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Food Allergy

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Food
ALLERGY

Commissioning Editor: Sue Hodgson
Development Editor: Sven Pinczewski
Editorial Assistant: John Leonard
Project Manager: Vinod Kumar Iyyappan
Design: Kirsteen Wright
Illustration Manager: Merlyn Harvey
Illustrator: Robert Britton
Marketing Managers (UK/USA): Gaynor Jones/Abigail Swartz

Food
ALLERGY
John M. James, MD
Colorado Allergy and Asthma Centers, P.C.
Private Clinical Practice
Fort Collins, CO, USA

Wesley Burks, MD
Professor and Chief
Pediatric Allergy and Immunology
Duke University Medical Center
Durham, NC, USA

Philippe Eigenmann, MD
Head, Pediatric Allergy Unit
Department of Child and Adolescent
University Hospitals of Geneva
Geneva, Switzerland

Edinburgh  London  New York  Oxford  Philadelphia  St Louis  
Sydney  Toronto  2012

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Notices
Knowledge and best practice in this field are constantly changing. As new research and experience broaden
our understanding, changes in research methods, professional practices, or medical treatment may become
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British Library Cataloguing in Publication Data
Food allergy.
  1. Food allergy.
  I. James, John. II. Burks, Wesley. III. Eigenmann, Philippe.
  616.9’75-dc22
ISBN-13: 9781437719925
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Preface

We take great pride in presenting an exciting new textbook entitled Food Allergy: Practical Clinical Approaches
to Diagnosis and Management. Our main goal was to create a practical, relevant and clinically-based
resource for food allergy and related adverse reactions to foods. The specific target audience was allergy
specialists, medical residents and fellows-in-training, general pediatricians, family physicians, nutritionists
and other health professionals with an interest in this important topic. Our hope was that the individual
chapters in this textbook would provide the reader with ready access to pertinent information. The chapters have been specifically templated with boxed key points, clinical pearls and case studies to help illustrate key teaching points. In addition, an accompanying web-based version of this textbook will be
available to all readers via secure access, with searchable text, images for download to use in presentation
and links to other online resources.
Food allergy is an important public health problem that affects children and adults and appears to be
increasing in prevalence. The impact of food allergy in the community is commonly underestimated.
Besides the few patients with potentially life-threatening reactions to trace amounts of foods, there are
large numbers of patients on eviction diets based on unclear diagnosis. Also because patients frequently
confuse nonallergic food reactions, such as food intolerance, with food allergies, there is an unfounded
belief among the public that food allergy prevalence is higher than the reality. The medical care team
works in the chasm between the public perception and scientific reality of food allergy. The rapid growth
in knowledge in this clinical area has been staggering and continues to be gratifying as reflected in the
topics covered in this textbook. While there is no current cure for food allergy (i.e. the disease can only
be managed by allergen avoidance or treatment of symptoms), there are exciting new developments in
potential new therapies. Topics addressed in this textbook include mucosal immunity and oral tolerance,
basic science of food antigens, epidemiology, diagnosis and management of food allergy, GI tract and
food allergy, natural history, as well as the management of food allergy and anaphylaxis. Hopefully, this
textbook will help to identify key gaps in the current scientific knowledge to be addressed through future
research, but also supply to the primary care provider clear guidelines on how to address a patient with
suspected food allergy.
The development and creation of this new textbook on food allergy would not have been possible
without the expert assistance of our contributing authors, as well as the excellent guidance and editorial
assistance from the expert staff at Elsevier Ltd. We certainly hope that the reader will find this resource
to be useful and practical in dealing with patients with food allergy and other adverse reactions to foods.
John M. James MD
Wesley Burks MD
and
Philippe Eigenmann MD

vii

List of contributors
Yuri Alexeev, PhD
Project Scientist
Institute of Food Research
Norwich
UK
Katrina J. Allen, MBBS, BMedSc, FRACP, PhD
Associate Professor
Paediatric Gastroenterologist/Allergist
Department of Paediatrics
University of Melbourne Royal Children’s Hospital
Group Leader
Gut and Liver Research Group
Infection, Immunity & Environment
Murdoch Children’s Research Institute
The Royal Children’s Hospital
Parkville, VIC
Australia

Jesús F. Crespo, MD, PhD
Allergy Specialist
Servicio de Alergia
Hospital Universitario 12 de Octubre
Instituto de Investigación Hospital 12 de Octubre
Madrid
Spain
George Du Toit, MBBCh, MSc, FCP, FRCPCH
Consultant in Paediatric Allergy
King’s College London
The Medical Research Council and Asthma UK
Centre in Allergic Mechanisms of Asthma
Division of Asthma, Allergy and Lung Biology
Guy’s and St Thomas’ National Health Service
Foundation Trust
London
UK

Cristiana Alonzi, MD
Assistant Professor
Food Allergy Referral Centre
Department of Pediatrics
Padua General University Hospital
Padua
Italy

Motohiro Ebisawa, MD, PhD
Department of Allergy
Clinical Research Center for Allergology and
Rheumatology
Sagamihara National Hospital
Sagamihara, Kanagawa
Japan

Dan Atkins, MD
Professor of Pediatrics
National Jewish Health
Associate Professor of Pediatrics
University of Colorado Medical School
Denver, CO
USA

Philippe Eigenmann, MD
Head, Pediatric Allergy Unit
Department of Child and Adolescent
University Hospitals of Geneva
Geneva
Switzerland

Debra D. Becton, MD
Assistant Professor of Pediatrics
University of Arkansas for Medical Sciences
Arkansas Children’s Hospital
Little Rock, AR
USA
S. Allan Bock, MD
Research Affiliate
Department of Pediatrics
National Jewish Health
Department of Pediatrics
University of Colorado Denver
Denver, CO
USA

Mary Feeney, MSc, RD
Clinical Research Dietitian
King’s College London and
Guy’s and St Thomas’ National Health Service
Foundation Trust
London
UK
Glenn T. Furuta, MD
Professor of Pediatrics
University of Colorado Denver School of Medicine
Department of Pediatrics
Digestive Health Institute, Section of Pediatric
Gastroenterology, Hepatology and Nutrition
Director, Gastrointestinal Eosinophilic Diseases
Program
The Children’s Hospital
National Jewish Health
Denver, CO
USA
ix

List of contributors
Contents
Jonathan O’B. Hourihane, DM, FRCPI
Professor and Head of Department
Paediatrics and Child Health
University College Cork
Cork
Ireland
John M. James, MD
Colorado Allergy and Asthma Centers, P.C.
Private Clinical Practice
Fort Collins, CO
USA
Philip E. Johnson, BSc(Hons), PhD
Postdoctoral Research Scientist
Institute of Food Research
Norwich
UK
Stacie M. Jones, MD
Professor of Pediatrics
Chief, Allergy and Immunology
Dr. and Mrs. Leeman King Chair in Pediatric
Allergy
University of Arkansas for Medical Sciences
Arkansas Children’s Hospital
Little Rock, AR
USA
Corinne Keet, MD, MS
Assistant Professor of Pediatrics
Johns Hopkins School of Medicine
Baltimore, MD
USA
John M. Kelso, MD
Division of Allergy, Asthma and Immunology
Scripps Clinic
San Diego, CA
USA
Jennifer J. Koplin, BSc
Murdoch Children’s Research Institute
Royal Children’s Hospital
Parkville, VIC
Australia
Gideon Lack, MBBCH (Oxon), MA (Oxon),
FRCPCH
Professor of Paediatric Allergy
King’s College London
The Medical Research Council and Asthma UK
Centre in Allergic Mechanisms of Asthma
Division of Asthma, Allergy and Lung Biology
Guy’s and St Thomas’ National Health Service
Foundation Trust
London
UK

x

Stephanie Ann Leonard, MD
Fellow
Jaffe Food Allergy Institute
Department of Pediatrics
Division of Allergy and Immunology
Mount Sinai School of Medicine
New York, NY
USA
Vicki McWilliam, BSci MND APD
Clinical Specialist Dietitian, APD
Department of Allergy and Immunology
Royal Children’s Hospital
Melbourne
Australia
E. N. Clare Mills, BSc PhD
Programme Leader
Institute of Food Research
Norwich
UK
Kim Mudd, RN, MSN, CCRP
Research Nurse/Program Coordinator
Johns Hopkins Division of Pediatric Allergy/
Immunology
Johns Hopkins Hospital
Baltimore, MD
USA
Antonella Muraro, MD, PhD
Head
Food Allergy Referral Centre Veneto Region
Department of Pediatrics
Padua General University Hospital
Padua
Italy
Anna Nowak-Wegrzyn, MD
Associate Professor of Pediatrics
Jaffe Food Allergy Institute
Department of Pediatrics
Division of Allergy and Immunology
Mount Sinai School of Medicine
New York, NY
USA
Tamara T. Perry, MD
Assistant Professor
Arkansas Children’s Hospital Research Institute
College of Medicine
Department of Pediatrics
University of Arkansas for Medical Sciences
Little Rock, AR
USA

List of contributors
stnetnoC
Julia Rodriguez, MD, PhD
Allergy Specialist
Head of the Allergy Service/Division
Servicio de Alergia
Hospital Universitario 12 de Octubre
Instituto de Investigación Hospital 12 de Octubre
Madrid
Spain
Hugh A. Sampson, MD
Professor of Pediatrics
Jaffe Food Allergy Institute
Division of Pediatric Allergy and Immunology
Mount Sinai School of Medicine
New York, NY
USA
Scott H. Sicherer, MD
Professor of Pediatrics
Jaffe Food Allergy Institute
Mount Sinai School of Medicine
New York, NY
USA

John O. Warner, MD, FRCP, FRCPCH, FMed Sci
Professor of Paediatrics and Head of Department,
Imperial College
Director of Research, Women and Children’s
Clinical Programme Group
Imperial College Healthcare NHS Trust
St. Mary’s Campus
London
UK
Jacqueline Wassenberg, MD
Chief Resident
Division of Allergology and Immunology
Department of Pediatrics
University Hospitals of Lausanne
Lausanne
Switzerland
Robert Wood, MD
Professor of Pediatrics and International Health
Johns Hopkins School of Medicine
Baltimore, MD
USA

Atsuo Urisu, MD, PhD
Professor
Department of Pediatrics
Fujita Health University
The Second Teaching Hospital
Nagoya
Japan

xi

Acknowledgments

There are so many individuals who have helped shape my career in medicine and my on-going professional development as a clinical specialist in Allergy, Asthma and Immunology. These include my clinic
staff, fellow staff physicians and partners and most importantly, my patients who have taught me so many
valuable lessons. In addition, I certainly could not have completed this textbook without the expert assistance of my co-editors, Dr. Wesley Burks and Dr. Philippe Eigenmann and the staff at Elsevier. Finally,
special acknowledgments should be made to my father, Dr. David James, who provided my initial inspiration to choose a career in medicine, Dr. Hugh Sampson, who was my clinical/research mentor during my
fellowship training at Johns Hopkins University in Baltimore, Dr. Wesley Burks, who was my first division
chief at the Univeristy of Arkansas for Medical Sciences in Little Rock, AR and to my wife, Kristie, and my
two children, Dylan and Maddie, who all have always supported me along my journey.
John James MD
I would like to thank the many patients and families with food allergy who have allowed me to learn
from them. Also, I want to thank the many mentors who helped guide and direct me, Dr. Rebecca Buckley,
Dr. Hugh Sampson, Dr. Jerry Winklestein and Dr. Hank Herrod; the advice they have given me has been
invaluable. Additionally I want to acknowledge my co-editors, Dr. John James and Dr. Philippe Eigenmann, without whom this project would not have been nearly as much fun. Lastly and most importantly
I want to thank my family, my wife, Jan, and our children Chris, Sarah and Collin for constant support
and encouragement.
Wesley Burks MD
I would like to thank the clinical staff and the research team at the University Children’s Hospital who
ease the many tasks of our daily work, also allowing activities such as editing a book, broadly seeding
knowledge on food allergy into the medical community. As in daily clinical practice or in research activities, this book would not have been possible without efficient and nice team work. My thanks go to Dr.
John James and Dr. Wesley Burks, the colleagues contributing the chapters, and the team at Elsevier. All
the knowledge shared in this book would not have been possible without education, and this gives me
the opportunity to thank among many mentors, Dr. Hubert Varonier who helped me to get on the tracks
of pediatric allergy, and Dr. Hugh Sampson whose support and education has been invaluable. Finally,
my wife Chantal and our children Alexandra and Oleg supported me in all ways in my professional
activities, many thanks to them.
Philippe Eigenmann MD

xiii

CHAPTER

1 

Overview of Mucosal Immunity and
Development of Oral Tolerance
Corinne Keet and Robert Wood

KEY CONCEPTS
The GI mucosa is the major immunologic site of contact
between the body and the external world.
 The manner in which immune cells encounter
antigen determines the subsequent immunologic
response.


Introduction
The mucosa is the principal site for the immune
system’s interaction with the outside environment.
Unlike the skin, which is characterized by many
layers of stratified epithelium, the intestinal mucosa
is lined with a single layer of columnar epithelium.
Almost two tons of food travel past this thin barrier
each year. More than one trillion bacteria representing about 500 distinct species live in contact with
it. The vast majority of these bacteria are nonpathogenic commensals, but pathogens lurk in this
diverse antigenic stew, and even the commensal
bacteria have the potential to cause harm if not kept
in check. The mucosal immune system performs
the essential job of policing this boundary and distinguishing friend from foe.
Not only must the mucosal immune system determine the local response to an antigen, but, as the
primary site of antigenic contact for the body, it also
plays a central role in directing the systemic response
to antigens. Oral tolerance – the modulation of the
© 2012, Elsevier Inc

Oral tolerance is a complicated process, probably
proceeding by several overlapping mechanisms.
 Many factors, including developmental stage, microbial
exposures, diet and genetics, influence the balance
between allergy and tolerance.


immune response to orally administered antigens
– is a fundamental task of the mucosal immune
system. In general, as befits the ratio of benign to
pathogenic antigens it encounters, the default
response of the mucosal immune system is tolerance. The tendency to tolerize to fed antigen can
even be used to overcome already developed systemic sensitization, something known and exploited
long before the specific cells comprising the immune
system were identified. Yet, despite the general bias
toward tolerance, the mucosal immune system is
capable of producing protective responses to pathogens. This response is controlled by recognition of
inherent characteristics of the antigen, or contextual
cues such as tissue damage. In general, the immune
system is remarkably skilled at responding properly
to the antigens it encounters. Failures, albeit uncommon, can be very serious. Food allergy is a prime
example of the failure of oral tolerance.
How the mucosal immune system determines
when to sound the alarm and when to remain
silent is the focus of this chapter. In it, we examine

Food Allergy

the normal response to food proteins, how that
response can go awry, and the factors that tip the
balance.

Structure and function
The primary role of the GI tract is to absorb food
and liquid and eliminate waste. To achieve this
goal, the surface of the tract is both enormous
(100 m2) and extremely thin. The lumen of the
intestinal tract provides a hospitable environment
for bacteria that help break down foods into absorbable nutrients. However, the thinness of the barrier
between external and internal creates a grave danger.
It is not just nutrients, but toxins, pathogenic bacteria, viruses and parasites that are kept out by a
single cell layer only. Breaks in this thin barrier
create a risk of systemic infection. The complex task
of protecting this border involves both non-specific
and highly targeted techniques.

Chemical defenses
Protection begins with chemical and physical measures that keep some of the potentially harmful antigens (both food and microbial) from contact with
the mucosal immune system and thus from generating an inflammatory response. Although the
intestinal lumen is one of the most microbiologically dense environments in the world, bacteria and
large antigens are actually maintained at some distance from the epithelial cells that line the GI tract.
This is accomplished by a rich glycocalyx mucin
layer (the mucus), which is produced by specialized
intestinal epithelial cells. Antimicrobial peptides
are caught in the mucous layer in a concentration
gradient that provides a zone of relative sterility
immediately proximal to the epithelial layer. In
mouse models, deficiency of either the mucins or
the antimicrobial peptides results in chronic inflammation. In humans, mutations causing abnormal
production of the antimicrobial peptides are associated with the autoimmune syndrome Crohn’s
disease.1,2 Whether dysfunction in the mucous
layer or antimicrobial peptides play a role in the
development of food allergy is an area yet to be
explored.
What is known is that the enzymatic degradation
of food proteins is a first line of protection against
allergic sensitization, and that defects in digestion

2

of food antigens contribute to allergy. Many food
proteins never get a chance to cause the systemic
immune responses characteristic of allergy because
they are labile and are denatured by the acidic contents of the stomach. Allergens tend to be proteins
that are resistant to this degradation, and thus
capable of reaching immune cells to cause sensitization and reaction. For example, β-lactoglobulin
and Ara h2, some of the relevant allergens for
milk and peanut allergy, respectively, are not
denatured by the conditions of the GI tract. Other
potential allergens, such as the birch homologs
found in many fruits, are easily broken down:
although they can induce oral symptoms in crossreactive individuals, they do not typically initiate
sensitization by themselves. Several studies have
lent evidence to the importance of the normal enzymatic processes in preventing allergy by showing
that antacids impair oral tolerance in both animals
and humans. Further, in mice, encapsulation of
potentially allergenic foods facilitated allergy by
allowing intact allergen to be present in the small
intestine.3
The fact that most proteins are broken down by
acid and enzymes may help explain why most
foods tend not to be allergens, but it does not
explain why allergy to stable proteins remains relatively rare. Peanut, for example, contains several
proteins that are not degraded, yet only about 1%
of the US population is allergic to it, despite near
universal exposure. Clearly, other factors come into
play after the digestive processes of the stomach.

Trafficking of antigen across
the epithelium
Proteins that are not degraded by enzymatic processes can come into contact with the immune
system in a number of ways. Transport across the
epithelium is both active and passive, occurring
both in the spaces between the cells and across
them (Fig. 1.1).
The high-volume route for fluid is via the paracellular spaces, and the overall permeability of the
mucosa is regulated by tight junctions that seal the
space between epithelial cells. The leakiness of
these junctions is subject to a variety of factors,
including cytokines, medications and nutritional
status. Permeability varies along the GI tract, and
even within a short area, as the pores of the villi
allow passage of larger solutes than those of the

Overview of Mucosal Immunity and Development of Oral Tolerance

A

1

C

Epithelial cell

M cell

B

Peyer’s patch
Lamina propria

Portal vein
Lymphatic

Liver

Mesenteric
lymph node

Spleen

A Dendritic cell route

B M cell route
Epithelial cell

Antigen

Antigen
Dendritic cell
M cell

C Epithelial cell route
Epithelial cell
Antigen

Follicle

Lamina propria

Lamina
propria

Germinal
center
Dendritic
cell
Lymphatic

T
cell

T
cell

T
cell

Macrophage
Capillary

IgA
Serosa

Lymphatic

Figure 1.1  Antigen sampling in the gut. (A) Dendritic cells sample antigen directly by extending processes into the lumen. (B)
Antigen taken up by M cells travels to the underlying Peyer’s patches. (C) Antigen can cross the epithelium for transport to
antigen-presenting cells, T cells, or into the lymphatic circulation. Reproduced with permission from: Chehade M, Mayer L. Oral
tolerance and its relation to food hypersensitivities. J Allergy Clin Immunol 2005; 115: 3–12.

3

Food Allergy

crypt.2,4 Cytokines associated with both autoimmune and allergic disease disrupt barrier function
and increase permeability.5 Children with food
allergy have been shown to have increased intestinal permeability, both at a time when they are
regularly consuming the relevant allergen and after
a long period of avoidance.6,7 Other evidence for
the importance of barrier function in allergy is the
high rate of new sensitization in people taking the
anti-rejection medicine tacrolimus, which causes
mucosal barrier dysfunction. Although tacrolimus
has other effects on the immune system, the high
rate of new food allergies after solid organ transplantation is thought to be due its effects on
mucosal integrity.5
In addition to the paracellular route, several
alternative transport systems actively carry proteins, electrolytes, fatty acids and sugars across
cells. Specialized modified epithelial cells called
M (or microfold) cells act as non-professional
antigen-presenting cells. These cells stud the
follicle-associated epithelium overlying specialized
collections of immune cells called Peyer’s patches.
They express receptors that recognize microbial
patterns and aid in the endocytosis and transfer of
antigen to the basal surface of the epithelium. This
is especially important for bacteria, but may also
be relevant for food allergens.4
Other non-specialized columnar epithelial cells
form vesicle-like structures that allow transport
of dietary proteins across cells. The formation
of these vesicle-like structures seems to be dependent on MHC class II binding, but transocytosis
can also occur via binding of antigen to IgA,
IgE, and IgG. Transport via IgE may be especially
important in the acute allergic response and in the
amplification of allergy.4 In contrast, secretory IgA,
which accounts for the majority of the immunoglobulin produced by the body, complexes with
antigen and facilitates transport across the epithelium to antigen-presenting cells, with a tolerogenic
outcome.
A final method of antigen transport involves
direct sampling of the luminal contents by extensions of antigen-presenting cells. Dendritic cells
found in the lamina propria form their own tight
junctions with intestinal epithelial cells and can
project directly into the intestinal lumen. These
projections increase when invasive bacteria are
present, and sampling via this route seems to be
especially important for the transport of commensal and invasive bacteria.4
4

Initial contact with the mucosal
immune system
Once the antigen has been captured by dendritic
cells, either by direct sampling or after processing
through epithelial cells, the fate of the immune
response depends on the interaction between dendritic cells and naive CD4+ T cells. Of the professional antigen cells associated with the gut, dendritic
cells are the most important. They are found
throughout the mucosal-associated lymph tissue
and comprise a large class of phenotypically and
functionally diverse cells. Subspecialization of these
cells is thought to depend on their derivation (some
develop from lymphoid precursors and some from
myeloid precursors), their maturity, and environmental cues. This interaction can occur in specialized aggregations of antigen-presenting cells, T cells
and B cells, such as Peyer’s patches, in the loose
aggregations of lymphocytes in the lamina propria,
or, most importantly for food antigens, in the
draining mesenteric lymph nodes.
Although there is communication between the
mucosal and systemic immune systems, contact
that is essential for both protective immune
responses and oral tolerance, there is significant
compartmentalization of responses at the mucosal
level. The mesenteric lymph nodes act as a ‘firewall’,
keeping the systemic immune system ignorant of
much of the local immune response. In animals
whose mesenteric lymph nodes have been removed,
massive splenomegaly and lymphadenopathy
develop in response to typical exposure to commensal organisms. In fact, much of the interaction
with commensal organisms never even reaches the
level of the mesenteric lymph nodes. IgA+ B cells,
which collectively produce the majority of the
immunoglobulin in the body, are activated at the
level of the Peyer’s patches and lamina propria and
act locally. Induction of this IgA response can
proceed normally in mice deficient in mesenteric
lymph nodes. Although the response to commensals happens largely at the level of the Peyer’s
patches and lamina propria, for food antigens it
seems that the mesenteric lymph nodes are key for
the active response that constitutes oral tolerance.
Mice without Peyer’s patches develop oral tolerance
normally, but those without mesenteric lymph
nodes cannot. For food antigens, it seems that the
typical path is for dendritic cells in the lamina
propria to traffic to the mesenteric lymph nodes for
presentation to CD4+ cells.7,8

Overview of Mucosal Immunity and Development of Oral Tolerance

Different experimental models have shown
somewhat different kinetics of traffic to mesenteric
lymph nodes after oral antigen. However, within
days after exposure, dendritic cells carry orally fed
antigen to the mesenteric lymph nodes and cause
T-cell proliferation. T cells stimulated in this way
then travel back to the mucosa and to the systemic
lymph nodes.9
Once captured and processed, antigen presented
by dendritic cells can cause several distinct immune
responses. It is this interaction that determines
whether allergy or oral tolerance develops.

What is oral tolerance?
Before we can begin to discuss what factors influence the development of oral tolerance, we must
discuss what is meant by oral tolerance. There is
disagreement at a fundamental level about how
oral tolerance to foods develops. Not only are the
specific mechanisms of oral tolerance imperfectly
understood, but also the overall paradigm. Here we
explore different theories about the development of
oral tolerance.

Immune deviation
Starting in the 1980s, with work from Coffman and
Mosmann, researchers began to describe distinct
subsets of CD4+ T cells that were characterized by
distinctive cytokine milieus and resulting disease or
protective states.10 A central paradigm in immunology for the past two decades has been this division
of effector CD4+ T cells into Th1 and Th2 cells,
both responsible for different mechanisms of clearing infection and both causing different pathological states when overactive. The cytokines that Th1
cells secrete (such as IFN-γ) activate macrophages
and facilitate clearance of intracellular pathogens.
In contrast, Th2 cells produce cytokines that
promote class switching and affinity maturation of
B cells, and signal mast cells and eosinophils to
activate and proliferate. Th2 responses are important for clearance of extracellular parasites.
Allergy is dominated by the Th2 response and is
characterized by IgE production, eosinophilia, mast
cell activation, and, in some cases, tissue fibrosis.
For many years it has been posited that the central
defect in allergy is an imbalance between Th1 and
Th2 responses. This model, although an oversimplification, has proved helpful in identifying factors

1

that promote allergy. In the original model naive
T-helper cells were stimulated by dendritic cells to
develop either as Th1 or Th2 cells. Cytokines necessary and sufficient for Th1 polarization include
IL-12 and INF-γ, but the mechanisms of Th2 differentiation have remained elusive. Two cytokines,
IL-4 and IL-13, play a role, but are not essential for
the development of high numbers of Th2 cells in
the mouse model. Until recently, a leading hypothesis was that Th2 differentiation is the default
response that occurs in the absence of Th1-directing
signals. The theory of Th2 as a default has appeal
because it harmonizes nicely with the so called
‘hygiene hypothesis’, in which inadequate infectious stimuli create the conditions for allergy. If Th2
deviation were the default, allergic responses would
naturally develop in the absence of Th1 driving
infectious stimuli. Recent work, however, suggests
that Th2 differentiation requires other signals,
including OX40L from dendritic cells, but that the
signals essential for Th1 differentiation are stronger
and predominate if present.11
Despite the compelling qualities of this theory, it
is now clear that the reality is much more complicated. Although allergy is characterized by a Th2
response, an increasing body of evidence calls into
question whether it is simply the balance between
Th1 and Th2 responses that lies at the crux of the
problem of allergy. Epidemiologic studies do not
consistently show a reciprocal relationship between
incidence of Th1 imbalance (i.e. autoimmunity)
and Th2 imbalance.12 Adoptive transfer of Th1 cells
in mice cannot control Th2-induced lung inflammation.13 A recent study showed that allergic subjects had low-level Th1-type cytokine responses to
allergenic stimulation that matched the nonallergenic responses but were simply overwhelmed
by the massive Th2 cytokine response.14 Most
importantly, other types of CD4 cells important in
the control of both allergy and autoimmunity have
been identified.

Regulatory T cells
The existence of T cells with suppressive capacity
was first recognized in the 1980s. Initially, centrally
derived T-regulatory cells were identified. These
cells are important in regulating autoimmunity and
are generated in the thymus, in a process of T-cell
selection that has been compared to Goldilocks’
sampling of the bears’ oatmeal. T cells with too
strong an attraction to self antigens are deleted, as
5

Food Allergy

Probability of selection

TCR avidity for self antigen

Death by neglect

Conventional CD4

TGF-β

Deletion

Foxp3+
Thymus

Foxp3

iTreg
RA
IL-6

Foxp3

TGF-β
Naive
CD4

nTreg

RORγt

Th17

Periphery

Figure 1.2  The development of regulatory T cells. In the thymus, avidity of the T-cell receptor for self antigen determines the fate of
the T cell. In the periphery, naive Foxp3− CD4+ T cells can develop into FoxP3+ T-regulatory cells or Th17 cells, depending on the
cytokine milieu. Reproduced with permission from: Mucida D, Park Y, Cheroutre H. From the diet to the nucleus: vitamin A and
TGF-beta join efforts at the mucosal interface of the intestine. Semin Immunol 2009; 21: 14–21.

are those that do not bind well at all, and thus will
not be effective antigen presenters. The majority of
the remaining cells bind ‘just right’ at a moderate
level and are destined to become effector T cells,
but a subset that binds to self antigens more strongly
persists and becomes suppressive T cells (Fig. 1.2).15
A transcription factor, FOXP3, is essential for the
suppressive nature of these cells and has served to
identify them. The importance of these cells in
autoimmune disease has been amply demonstrated, both in animal models – autoimmune
disease can be induced by depletion of these cells
– and in natural human diseases. Children with
IPEX (immune dysregulation, polyendocrinopathy,
6

enteropathy, X-linked) syndrome have mutations
in the FOXP3 gene leading to absent or abnormal
levels of regulatory T cells. These children have
early and severe autoimmune gastrointestinal and
endocrine disease. Bone-marrow transplant that
replaces the T-regulatory cells successfully reverses
the disease.
Children with IPEX also have food allergy and
eczema, demonstrating a failure of tolerance to
antigens that are not present in the thymus. More
recently, the importance of peripherally generated
T-regulatory cells has become clear. As with the
centrally generated T-regulatory cells, FoxP3 marks
these cells (called iTregs), although other related

Overview of Mucosal Immunity and Development of Oral Tolerance

subsets of suppressor T cells generated in the
periphery do not express Fox P3. T-regulatory cells
are preferentially induced in the mesenteric lymph
nodes, where the cytokine TGF-β is a key mediator
of T-cell differentiation. In the past decade, it has
been determined that T-regulatory cells and a newly
described T-cell subset, Th17 cells, develop reciprocally under the influence of TGF-β. A cytokine, IL-6,
drives differentiation to Th17 cells, whereas a
metabolite of vitamin A, retinoic acid, was recently
discovered to inhibit Th17 differentiation and
promote T-regulatory development in the presence
of TGF-β.16 Vitamin A, which is not produced by
the human body, is converted to its active form,
retinoic acid, by epithelial cells and dendritic cells.
The fact that generation of suppressor cells is

1

dependent on an orally derived factor that is converted to an active form by the intestinal epithelium
may help explain how the gut is maintained as a
tolerogenic site.17
Peripherally generated T-regulatory cells have a
multitude of effects on other immune cells. Through
the action of secreted cytokines, such as IL-10 and
TGF-β, they act on B cells, reducing IgE production
and inducing the blocking antibody IgG4; on Th1
and Th2 cells, suppressing their inflammatory activities; and on dendritic cells, inducing them to
produce IL-10 and further stimulate the development of regulatory T cells. In addition, they have
direct interaction with mast cells through cell
surface ligands (Fig. 1.3). In sum, they control both
Th1- and Th2-mediated inflammatory responses.18

Induction of IgG4
suppression of IgE

Suppression of
inflammatory DC induction
of Treg cell stimulating APC

B cell
DC

IL-10
TGF-β

Suppression of
Th2 effector cells

IL-10
TGF-β

TH2
CTLA-4
PD-1
HR2
OX40
OX40L

Mast
cell

Basophil

IL-10
TReg
IL-10
TGF-β
IL-10
TGF-β

Eosinophil

Th0
TH1
Suppression of
Th1 effector cells

Interaction with
resident tissue cells,
role in remodeling

Direct and indirect suppressive
effects on mast cells, basophils
and eosinophils

Figure 1.3  T-regulatory cells have direct and indirect effects on many different types of effector cells. Suppressive cytokines include
interleukin-10 (IL-10) and transforming growth factor-β (TGF-β). Another mechanism of suppression is by cell–cell contact via
OX40-OX40ligand (red arrows: suppression; black arrows: induction). Reproduced with permission from: Akdis M. Immune tolerance
in allergy. Curr Opin Immunol 2009; 21: 700–7.
7

Food Allergy

Antigen-specific peripherally induced T cells
are essential for oral tolerance. Oral tolerance proceeds normally in mice lacking centrally derived
T-regulatory cells, but fails in mice unable to
induce regulatory cells peripherally.16 In humans,
T-regulatory cell function has been implicated in
both IgE- and non-IgE mediated food allergy. Children with active non-IgE mediated milk allergy had
lower T-regulatory cells than controls in one study,
whereas another, also of non-IgE mediated milk
allergy, showed that T-regulatory function was associated with outgrowing the disease. In IgE-mediated
milk allergy, increased numbers of T-regulatory
cells were found in children with a milder phenotype who were better able to tolerate cooked milk
than those with a more severe phenotype who
reacted to cooked milk.6
T-regulatory cells seem also to be important
for the effectiveness of allergen-specific immunotherapy. Oral and sublingual immunotherapies
(reviewed in Chapter 17) have emerged as a very
promising treatment for food allergy. Although the
precise mechanisms by which they work are not yet
known, an increase in FOXP3+ T-regulatory cells
was found in the initial stages of peanut immunotherapy, with a return to baseline by 2 years on
therapy.6
Th17 cells, which develop reciprocally with
T-regulatory cells, promote inflammatory responses
at the gut and seem to be especially important for
protection against infection.19 Deficiency of Th17
cells, as in Job’s syndrome (also known as hyper-IgE
syndrome), is characterized by abnormal responses
to infectious stimuli, as well as very high levels of
IgE. However, despite these high levels, specific sensitization is less common and the causes of high
IgE in this syndrome are not clear.20 Th17 cells do
seem to be important in certain types of asthma
that are less atopic, but whether they have a role in
either prevention or promotion of food allergy has
not been determined.

Other methods of tolerance
Other mechanisms of oral tolerance overlap with
those discussed above. For control of self-reactivity,
besides deviation and responsiveness to suppression, T cells have other mechanisms that allow
them to be switched off or killed. In general, activation of the cell in the absence of co-stimulatory
signals results in anergy. Anergy refers to a T-cell
state where proliferation to antigen on rechallenge
8

is impaired, but can be reversed with sufficient
quantities of the T-cell growth cytokine IL-2. Blockage of co-stimulatory receptors can induce anergy,
as can other methods of TCR cross-linking without
co-stimulation, such as stimulation with soluble
peptides. Deletion is a related process, and can
follow anergy.
Several studies have shown that anergy and deletion can be important in oral tolerance to food
antigens. In a key paper, Chen and colleagues21
found that high doses of a model antigen caused
initial activation of T cells followed by apoptosis of
antigen-specific T cells. Low doses led to increases
in what we now know to be regulatory T cells.
Similarly, Gregerson et al.,22 in a model of autoimmune uveoretinitis, found that low doses of fed
antigen caused suppressive mechanisms to kick in,
and that transfer of lymphocytes from treated
animals transferred suppression to untreated
animals. At higher doses, anergy was the predominant mechanism, and this could not be transferred
to a naive animal.
Anergy, apoptosis and suppressive mechanisms
are not mutually exclusive and have been shown to
work simultaneously.23,24 In all likelihood, the
normal response to food proteins involves a combination of immune deviation, regulatory factors
and anergy/deletion of reactive clones. It makes
sense that something as important as oral tolerance
would have highly redundant mechanisms.

Factors that influence the
development of oral tolerance
versus allergy
Factors both intrinsic to the individual and related
to environmental exposures influence the development of allergy. Those that have been identified so
far include age, microbial exposures, genetics, nutritional factors, and dose and route of antigen.

Developmental stage
The neonatal GI tract differs from the adult tract
in significant ways, including the robustness of
physical and chemical barriers, the composition of
the microbial flora, and the maturity of the gutassociated immune system. Overall, these differences predispose the infant to the development of
allergy, although the precise developmental window

Overview of Mucosal Immunity and Development of Oral Tolerance

of risk and the optimal strategy to prevent allergy
in infants are among the most contentious areas in
the field of allergy.
Part of the difficulty of resolving these controversies lies in the inadequacy of the animal models.
Both human and rodent neonates have increased
intestinal permeability compared to their adult
counterparts. However, in humans, the transition
from the highly permeable fetal gut to a more
mature gut barrier occurs in the first few days of life,
compared to more than a month in rats.25
One well-studied area is the difference in gastric
pH and pancreatic enzyme output between infants
and adults. With their immature barriers to regurgitation of caustic gastric contents, infants secrete
much less acid into the stomach and have decreased
pancreatic enzyme output, and do not reach adult
levels of pH for the first few years of life.25 As discussed above, acidic and enzymatic digestion is a
first-line defense preventing some potentially sensitizing proteins from reaching relevant immune
cells. Combined with somewhat increased intestinal permeability, this increases the chances of intact
allergen crossing the epithelial border.
Once across the epithelial border, the immune
system that the antigen encounters is very different
in neonates than in adults. Both cellular and
humoral branches of the immune system are immature. Total numbers of dendritic cells are lower, as
is their ability to respond to co-stimulatory factors
that typically elicit a Th1-type response. Further,
CD4+ T cells are themselves highly skewed in a Th2
direction in the neonate, and have poor production
of IL-12, a cytokine involved in Th1 responses. The
inability to mount Th1 responses but ability to
mount Th2 responses leads to an environment
where potential autoimmunity or reactivity to
maternal antigens is dampened, responses to
microbial insults are deficient, and allergic responses
are relatively favored.26
The fetal and neonatal immune system is also
characterized by varying levels of T-regulatory cell
function. At the time of birth, T-regulatory cells are
found less frequently in cord blood than in adult
blood, and those found have less efficient suppressive function after stimulation.28 However, there is
some evidence that, at least in mice, neonatal T cells
have a propensity to develop into T-regulatory
cells.27 Given the uniquely stressful experience of
birth, one could question whether what is found in
cord blood is a valid reflection of the intrinsic qualities of the neonate. Regardless, the T-regulatory cell

1

compartment is one area where neonatal and adult
responses vary considerably, with important implications for the development of allergy.
The humoral immune system is also immature in
the infant. Immaturity of the humoral immune
system is at least partially compensated for by
unique features of breast milk. Breast milk contains
large amounts of secretory IgA and some IgG.
Maternally supplied IgA substitutes for the infant’s
relative lack, complexing with dietary proteins
and promoting non-inflammatory responses.25 IgG
found in breast milk plays a similar role, with
added nuances. Neonates express a receptor for IgG
in their intestinal epithelium (the FcRn receptor).
This allows for active transport of IgG from breast
milk into the neonatal circulation. In addition to
absorbing maternal antibody to be used in fighting
infections, the FcRn receptor can also transport
intact antigen complexed with IgG directly from the
lumen to lamina propria dendritic cells, contributing to oral tolerance. In mice, antigen complexed
to IgG in breast milk has been shown to induce
antigen-specific T-regulatory cells in a manner independent of the other ingredients in breast milk.
Interestingly, this was enhanced in mothers who
were sensitized to the allergen.29
Other components of breast milk are important
in oral tolerance. Pro-forms of the tolerogenic
cytokine TGF-β are abundant in breast milk. They
are thought to be physiologically active after exposure to the acidic gastric environment, and epidemiologic work in humans suggests that higher
levels are associated with protection from atopic
disease.30,31
Despite these pro-tolerogenic features, the presence of allergen in breast milk does not always lead
to oral tolerance. Allergens are found both free and
complexed to antibody in breast milk, and infants
can become sensitized to proteins encountered in
breast milk and react to them. Complicating the
picture further, maternally ingested or inhaled allergens have also been found in the placenta, although
whether this allergen is transferred to the fetal circulation remains unclear. Studies in mice have
shown variation in the results of prenatal exposure
by the dose of antigen. Mice whose mothers had low
doses of prenatal exposure to a model allergen
developed tolerance to that allergen. With higher
doses there was transient inhibition of IgE production upon challenge, but after the immediate neonatal period the mice had increased susceptibility
to the development of allergy to that allergen.32
9

Food Allergy

Whether sensitization or oral tolerance to these
antigens occurs probably depends on a complex
interaction between the non-allergen components
of breast milk, infant factors, and the dose and
timing of the allergen.

Route of exposure
Some have suggested that the primary route of sensitization leading to food allergy is via the skin. In
this model, oral exposure is almost always tolerogenic. Allergy happens when the skin encounters
potentially allergenic foods prior to oral contact.
Eczema, which creates breaks in the skin and an
inflammatory backdrop, predisposes to allergic sensitization. Evidence supporting this model includes
the fact that mice can be sensitized via low-dose
skin exposure, some epidemiologic evidence tying
peanut oil-containing lotions to peanut allergy, and
the differences in immune responses induced by
antigen-presenting cells in the skin and in the gut.
However, this theory has not been conclusively
proven.33

Microbial influences
The most compelling theory for the wide variation
in incidence in allergic disease remains the so called
‘hygiene hypothesis’. In general terms, this theory
posits that the decreased burden of infection, especially childhood infections, characteristic of the
western lifestyle does not adequately stimulate the
developing immune system into a non-allergic phenotype. The beauty – and the limitation – of this
theory is that it is sufficiently broad to encompass
a wide range of theoretical mechanisms by which
infection might prevent allergy, including Th1
skewing and induction of T-regulatory cells, and
that it does not specify what infections are actually
essential.
Epidemiologic evidence supporting the hypothesis includes the fact that allergy is more common in
developed than in developing countries, in city than
in farming communities, in children who do not
attend daycare, and in older siblings than in younger
siblings, especially younger siblings in large families. A thorough analysis of farming communities in
Europe identified unpasteurized milk and the presence of multiple species of farm animals living
under the same roof as key protective factors of the
rural life. In other populations, markers for parasitic
infections, such as Schistosoma, are associated with
10

reduced rates of allergy. In addition, differences in
the microbial content of drinking water have been
linked to the disparate rates of atopic disease found
in genetically similar populations of people living
on different sides of the Finnish/Russian border.
Similar epidemiologic studies also associate infection with protection from autoimmune disease.34
Evidence tying actual differences in gut flora to
allergy has been mixed, with some finding that
allergic children have different colonization patterns, and others failing to replicate the result. Birth
by Caesarean section, which does not expose the
infant to the normal maternal vaginal and fecal
flora, has been associated with alterations in the
infant’s fecal flora. In one study,35 Caesarean delivery was associated with an increased risk of wheezing, although this was not replicated in another
study. Methodological problems with how gut flora
were analyzed may be a part of the confusion, as
the relevant bacteria may be hard to culture.
In rodent models, intestinal colonization is
essential for normal development of the immune
system and for the ability to induce oral tolerance.
Recent work has identified certain bacterial components as being essential for the development of the
normal gut immune system.36 Specific mechanisms
for prevention of allergy by infection are still being
worked out. In humans, the mechanisms have been
most carefully explored in prospective studies of
children growing up on European farms. In these
studies, several mechanisms of protection from
allergy were identified, including upregulation of
Toll-like receptors (TLRS), increased T-regulatory
cell function and alterations in prenatal serum
cytokine levels.37–39 Prenatal farm exposure has
been identified as particularly protective for the
development of allergy. Whether the prenatal
exposure is mediated by colonization of the infant,
epigenetic changes passed from mother to child, or
by so far unidentified features of the intrauterine
environment, is unknown.

Nutritional factors
Nutritional factors are one way in which the prenatal
environment or early life could modify the risk for
allergic disease. Because diet has changed so rapidly
in developed countries over the last half century,
nutritional factors are candidates to explain the
rapid increase in allergic disease and the geographic
variation in disease. The Mediterranean diet in
general during pregnancy has been associated with

Overview of Mucosal Immunity and Development of Oral Tolerance

protection from respiratory allergy and wheeze in
children.40 It has been suggested that an important
difference between more ‘westernized’ diets and the
Mediterranean diet is the presence of different isoforms of vitamin E found in cooking oils. D-αtocopherol, found in olive oil and sunflower oil, has
anti-inflammatory effects by reducing cell adhesion
molecules on epithelial cells. D-γ-tocopherol, the
predominant isoform of vitamin E found in vegetable oils in westernized diets, has opposite effects on
epithelial cells.41 The effects of these isoforms on
food allergy have not been adequately explored.
Another dietary factor that may have a role in
protection from allergy is polyunsaturated fatty
acids (such as those found in fish oil). In a randomized placebo-controlled study, supplementation
with omega-3 polyunsaturated fatty acids during
pregnancy and breastfeeding was associated with
lower sensitization to food proteins and eczema.42
Epidemiologic studies have found similar results,
although not uniformly.43
Besides fatty acids, vitamin D is also found in fish
oil. Vitamin D levels vary significantly within westernized populations. Vitamin D is found in the
diet, both naturally in foods such as fatty fish and
in fortified dairy products, and is also produced by
the skin with exposure to sun. Populations living at
very northern or southern latitudes, as is the case
in most developed countries, are at risk for deficiency. Vitamin D is a steroid hormone with pleotropic effects. Its many effects on the immune
system can vary by dose. To innate cells, it promotes
the production of antimicrobial peptides, while
also downregulating some TLRs. The effects on Th1
cells include downregulation of IFN-γ at the gene
level. Effects on Th2 cells depend on the dose, with
very high or low levels associated with increased
Th2 deviation. Overall, T-regulatory cells are upregulated. Epidemiologic studies of the relationship
between vitamin D supplementation and allergy or
wheeze have found mixed results, and have typically been very susceptible to recall bias. Several
recent population studies have linked latitude and
season of birth with acute food allergy episodes,
implicating lack of sun exposure in the pathogenesis of food allergy. Studies that prospectively assess
the relationship between vitamin D and development of allergy are under way.44,45
Vitamin A, which has a clear role in the development of oral tolerance, is found in sufficient
amounts in almost all western diets. Blood levels
are tightly controlled, and so although vitamin A

1

may be necessary for the development of oral tolerance, differences in intake may not be an important
risk factor for food allergy. Whether variations in
intake relate to the development of oral tolerance
has not been explored.
The role of folic acid in allergy and asthma is
another area of intense study, although its specific
role in oral tolerance has not been determined. The
interest in folic acid is driven by its potential role
in the modification of DNA expression through epigenetics, and by the fact that folic acid intake has
changed markedly in the past two decades. Epigenetics refers to heritable changes in gene expression
that are not due to changes in the underlying DNA
sequence. The major mechanism of epigenetic
change is through changes in methylation of DNA.
Folic acid, which is a methyl donor, was added to
all grain products in the US in 1998 by FDA
mandate. In 2008, Hollingsworth et al.46 showed in
a mouse model that maternal supplementation
with folate led to suppression of a gene known to
be important for the balance between Th1 and Th2
skewing, among other effects. In contrast, in a
cross-sectional epidemiologic study, Matsui and
Matsui47 found an inverse relationship between
folic acid levels and total IgE, atopy and wheeze.
The role of folic acid in allergy and airway disease
remains highly controversial.

Genetics
A family history of food allergy in particular, and
atopy in general, is a major risk factor for the development of food allergy. Teasing apart the role of
environment and genetics in failures of oral tolerance has been complicated by the lack of uniform
definitions for food allergy, and by the probability
that what we call food allergy actually comprises
several distinct phenotypes. Further, as has been
demonstrated best for asthma, it is likely that gene
–environment interactions mandate precise determinations of environmental factors when trying to
determine the role of genetics (and vice versa). For
example, in studies of asthma, a genetic variant in
the receptor for lipopolysaccharide (a bacterial
product important in stimulating innate immune
responses) is protective at high levels of endotoxin
(such as might be found on a farm), but increases
the risk of asthma when levels of endotoxin are
low.48 Exposure to both microbial products and
allergens probably modifies whatever genetic risk
factors there are for food allergy.
11

Food Allergy

However, no matter how it is defined, and under
what environmental conditions, it is clear that there
is a large genetic component to food allergy. For
example, a British study found that a child with a
peanut-allergic sibling had a five times increased
risk of peanut allergy than the general population.
Depending on how food allergy is defined, and on
the population studied, the heritability of specific
food allergies has been estimated to be 15–80%.48
Despite the clear heritability of food allergy, it is not
yet clear which genes are most important for the
normal development of oral tolerance. The genes
that most obviously cause food allergy when
mutated, such as FOXP3, in which food allergy is
part of a larger syndrome, are probably only responsible for a fraction of the overall burden of disease.
Candidate genes that have been explored with
varying levels of success include those for antigen
presentation, cytokines, and intracellular signaling.
Human leukocyte antigens, which determine the
antigenic epitopes presented to the immune system,
were early targets for study. Although initial studies
showed an association with certain food allergies,
repeat studies did not replicate those results. Two
genes known to be involved in Th2 differentiation,
SPINK5 (serine protease inhibitor Karzal type 5)
and the gene for IL-13, have shown association with
food allergy in preliminary studies. Studies of two
other genes that would be logical to be involved,
the gene for the receptor for lipopolysaccharide,
discussed above, and the gene for IL-10 (which is
important in T-regulatory cell development), have
found inconsistent results. Larger studies are under
way to try to further elucidate the genetic factors
important in the normal development of food
tolerance.48
In summary, the balance between oral tolerance
and allergy is influenced by a complicated array of
factors, including genetic susceptibility, microbial
exposure, dietary factors, and the route, dose and
timing of allergen exposure. Environmental influences begin in the womb, and perhaps before, and
are modified by the mother’s genetics and own
allergic history. So far we have only scratched the
surface of this field.

Opportunities for prevention
With the steep rise in allergy in general, and food
allergy in particular, the need for interventions that
might prevent allergy has become more imperative.
12

However, implementing a successful preventive
strategy is like threading a narrow needle: any intervention can have unintended consequences. So far,
preventive strategies have focused most heavily on
the timing of antigen exposure, with some attention to trying to alter the gut flora and to nonallergen related dietary factors.
The history of recommendations about the
timing of allergen exposure serves as a cautionary
tale about the dangers of making policy for populations without clear evidence. Although previous
AAP recommendations suggested that pregnant and
lactating women with a family history of allergy
avoid peanuts and tree nuts, and possibly eggs, fish
and milk, more recent reviews of the literature have
concluded that there is no good evidence that
maternal avoidance is beneficial. Indeed, small
interventional studies have suggested that maternal
avoidance is not risk-free, and that maternal egg
and milk avoidance can be harmful nutritionally.
The most recent advisory statement by the AAP
retracts the previous recommendation, stating
instead that there are not enough data to make any
recommendation.49
The best time to introduce allergens directly to
the infant is even more contentious. Previous recommendations were that at-risk children avoid
cows’ milk until their first birthday, egg until the
second, and peanut, tree nuts and fish until the
third. In the decade since those recommendations
were made in the US and the UK, the incidence of
food allergy has continued to grow rapidly, and
prominent allergists are questioning whether more
harm than good is being done by avoiding allergens
early in life. Some tentative epidemiologic evidence
supports the notion that early introduction could
be helpful. Evidence includes the low rate of peanut
allergy in Israel, where peanuts are eaten early, compared to the high rate in genetically similar populations in the UK, where peanuts typically are not
eaten early. A large interventional study of early
peanut introduction in children with eczema or egg
allergy currently under way in the UK will hopefully
shed light on this question. In the meantime, pediatricians, allergists and parents are left without clear
guidance about when to start highly allergenic
foods.
Probiotics for the prevention of allergy are
another area where initial high promises have not
been met. Given the data for the importance of gut
microbiota in the development of the intestinal
immune response, it would make sense that one

Overview of Mucosal Immunity and Development of Oral Tolerance

could alter the microbial contents with beneficial
results. Prebiotics, which contain elements that
stimulate specific bacterial growth, and probiotics,
which contain the bacteria themselves, have been
used in many small studies for the prevention and
treatment of allergic disease. In sum, the studies
suggest a small beneficial effect for the prevention
of atopic dermatitis, but no benefit for the treatment of established disease or for the prevention of
other atopic conditions. Larger, well-designed
studies are required before probiotics can be confidently recommended.50
Other dietary factors are promising, although
they have not yet been fully evaluated. As discussed
above, the single randomized controlled study of
fish oil found some protection from food allergy,
but this needs to be replicated. It is not yet clear
whether an increase or reduction in vitamin D and
folic acid would be the best intervention for prevention of food allergy. Well-designed prospective epidemiologic studies are the first necessary step to
sort this out.

Conclusions
Oral tolerance is a complex, active process that
occurs in the gut-associated immune system.
Although the precise mechanisms have not been
completely elucidated, regulatory T cells seem to be
essential for its development and maintenance.
Other, overlapping mechanisms, including immune
deviation, anergy and deletion, also play a role.
Many factors affect the balance between allergy and
oral tolerance. They include genetic variations, the
dose, timing and route of antigen exposure, the
microbial milieu, and probably other dietary
factors. This field is still young, and much remains
to be done to identify the mechanisms of allergic
sensitization. Because of the complexity of the
system, some things will not be known until interventional studies in humans are carried out.

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17. Strober W. Vitamin A rewrites the ABCs of oral
tolerance. Mucosal Immunol 2008;1:92–5.
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19. Weaver CT, Hatton RD. Interplay between the TH17
and TReg cell lineages: a (co-)evolutionary perspective.
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T(H)17 cell differentiation in subjects with autosomal
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773–6.
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22. Gregerson DS, Obritsch WF, Donoso LA. Oral tolerance
in experimental autoimmune uveoretinitis. Distinct
mechanisms of resistance are induced by low dose vs
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23. Perruche S, Zhang P, Liu Y, et al. CD3-specific
antibody-induced immune tolerance involves
transforming growth factor-beta from phagocytes
digesting apoptotic T cells. Nat Med 2008;14:528–35.
24. Sun JB, Czerkinsky C, Holmgren J. Sublingual ‘oral
tolerance’ induction with antigen conjugated to cholera
toxin B subunit generates regulatory T cells that induce
apoptosis and depletion of effector T cells. Scand J
Immunol 2007;66:278–86.
25. Verhasselt V. Oral tolerance in neonates: from basics to
potential prevention of allergic disease. Mucosal
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immunity: faulty T-helpers and the shortcomings of
dendritic cells. Trends Immunol 2009;30:585–91.
27. Wang G, Miyahara Y, Guo Z, et al. ‘Default’ generation
of neonatal regulatory T cells. J Immunol 2010;185:
71–8.
28. Schaub B, Liu J, Schleich I, et al. Impairment of T
helper and T regulatory cell responses at birth. Allergy
2008;63:1438–47.
29. Mosconi E, Rekima A, Seitz-Polski B, et al. Breast milk
immune complexes are potent inducers of oral
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development. Mucosal Immunol 2010;3:461–74.
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transforming growth factor-beta in the prevention of
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importance of milk TGF-beta on immunological
outcomes in the infant and young child. Pediatr
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to a farm environment modifies atopic sensitization at

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birth. J Allergy Clin Immunol 2008;122:407–12, 12
e1–4.
38. Schaub B, Liu J, Hoppler S, et al. Maternal farm
exposure modulates neonatal immune mechanisms
through regulatory T cells. J Allergy Clin Immunol
2009;123:774–82 e5.
39. Pfefferle PI, Buchele G, Blumer N, et al. Cord blood
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pregnancy: the PASTURE Study. J Allergy Clin Immunol
2010;125:108–15 e1–3.
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diet in pregnancy is protective for wheeze and atopy in
childhood. Thorax 2008;63:507–13.
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Isoforms of vitamin E have opposing immunoregulatory
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recruitment. J Immunol 2009;182:4395–405.
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supplementation in pregnancy and lactation may
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2009;98:1461–7.
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postnatal dietary exposures on childhood development
of atopic disease. Curr Opin Allergy Clin Immunol
2010;10:139–44.
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Mol Biol 2010;120:86–95.
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birth and food-induced anaphylaxis in Boston. Allergy
2010;65:1492–3.
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47. Matsui EC, Matsui W. Higher serum folate levels are
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48. Hong X, Tsai HJ, Wang X. Genetics of food allergy.
Curr Opin Pediatr 2009;21:770–6.
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nutritional interventions on the development of atopic
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50. Johannsen H, Prescott SL. Practical prebiotics,
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they? Clin Exp Allergy 2009;39:1801–14.

CHAPTER

2 

Food Antigens
E. N. Clare Mills, Philip E. Johnson, Yuri Alexeev

Introduction
The immune system possesses remarkable flexibility in the number of ways in which it works to
protect the body from hazards, including infective
microorganisms, viruses and parasites, employing
both cellular agents to remove and inactivate
hazards, as well as molecules, notably immunoglobulins (Igs), which form part of the humoral
defense system. Igs are synthesized in a number of
different forms, or isotypes, and have been classified on a structural, physicochemical and functional
basis including IgA, IgG (of which there are a
number of subtypes identified in humans, including IgG1 and IgG4), IgM and IgE. All are characterized by an antibody-binding site generated to bind
specifically to ‘non-self’ molecules, which are generally known as antigens. These include molecules
found in microbial pathogens, parasites, environmental agents such as pollen and dietary proteins.
Albeit not exclusively so, antigens tend almost
entirely to be proteinaceous in nature, although
some carbohydrate moieties can be recognized, and
the lipopolysaccharide antigens of microbes are
particularly effective elicitors of humoral immune
responses.
However, in the allergic condition classified as a
type I hypersensitivity reaction, the antibody repertoire to selected environmental antigens is altered,
the body synthesizing larger quantities of the antibody isotype normally produced in response to
© 2012, Elsevier Inc

parasitic infections, IgE. The molecules recognized
by IgE are frequently termed allergens and, if polyvalent in nature, they may be able to cross-link
mast-cell-bound IgE and in so doing trigger mediator release, the inflammatory mediators then going
on to trigger tissues responses which are manifested
as allergic symptoms in an allergic reaction.
The sites that an antibody recognizes on its
cognate antigen have been termed epitopes and can
be classified into two different types. The first of
these have been termed continuous or linear
epitopes and are where antibody recognition is
based almost entirely on the amino acid sequence,
with very little effect of conformation. In general
such antibodies can bind well to short linear peptides of 10–15 residues in length that correspond
to the epitope sequence in the parent protein. They
also often recognize both native folded and
unfolded antigens well. A second type of epitope
has been termed conformational and is where the
secondary, tertiary and quaternary structural elements of a protein antigen bring together sometimes quite distant regions of the polypeptide
chain. In general, antibody binding to such epitopes
is disrupted when proteins unfold, and it can be
difficult to map such epitopes using linear peptides
as they do not resemble the structural epitopes
brought about by the folded nature of the antigen.
Structural studies have indicated that antibody
binding to proteins involves a surface area of 650–
900 Å2, contacts outside the immediate epitope

Food Allergy

area being important in binding although they
may not determine antibody specificity. Such definitions are in some ways arbitrary, and it may be
in some instances that several linear epitopes
could come together to form a conformational
epitope.
Allergens have been defined by the International
Union of Immunological Societies as being molecules that must induce IgE-mediated (atopic)
allergy in humans with a prevalence of IgE reactivity
above 5%. Although it does not carry any connotation of allergenic potency, an allergen is termed as
being major if it is recognized by IgE from at least
50% of a cohort of allergic individuals, otherwise it
is known as minor. Allergens are given a designation based on the Latin name of the species from
which they originate and composed of the first
three letters of the genus, followed by the first letter
of the species and finishing with an Arabic number.
Thus, an allergen from Mallus domesticus (apple) is
prefaced Mal d followed by a number, which is
largely determined by the order in which allergens
are identified. The numbers are common to all
homologous allergens (also known as isoallergens)
in a given species, which are defined on the basis
of having a similar molecular mass, an identical
biological function, if known, e.g. enzymatic action,
and >67% identity of amino acid sequences. For
those species where the first three letters of a genus
and the first letter of a species are identical, the
second letter of the species is also used.
Many proteins are post-translationally modified
with glycans and such structures can bind IgE,
glycan-reactive IgE being found in between 16%
and 55% of food-allergic patients. These are best
characterized for the asparagine-linked carbohydrate moieties (N-glycans), with α(1–3) fucose and
β(1–2) xylose representing the major cross-reactive
carbohydrate determinants (CCDs), which are
found in many plant food and pollen allergens but
are distinct to mammalian N-glycans. However,
there is debate about whether IgE to CCDs has biological significance, and whether it can result in
clinically significant allergic symptoms. This is
probably because such glycans tend not to be polyvalent, and consequently are unable to trigger crosslinking of IgE receptors, the IgE binding may be of
low IgE affinity, and the presence of blocking antibodies may downregulate the allergic response.
O-linked glycans are also found in plant proteins,
albeit less frequently than N-glycans. There is evidence that single β-arabinosyl residues linked to
16

hydroxyproline residues are important in determining the IgE-binding activity of an allergen from
mugwort pollen known as Art v 1, although O-linked
glycans have yet to be described in food allergens.
In the process of describing the active agents
involved in food allergies a large number of allergens have now been identified with the greatest
diversity existing for plant food allergens, perhaps
reflecting the diversity of plant-derived foods that
humans consume. They include nuts, seeds, grains,
and a variety of fresh fruits and vegetables. Although
it appears that individuals can be allergic to any of
a vast number of foods, it appears that the majority
of allergies are triggered by a more restricted selection, and that the allergens triggering those reactions belong to a restricted number and type of
protein. This observation has led to certain restricted
numbers of foods being termed the ‘Big 8’ which
includes milk, eggs, fish, crustacean shellfish, tree
nuts, peanuts, wheat and soybean. Other important
allergenic foods or food groups have emerged,
some of which, along with the ‘Big 8’ must be
labeled on manufactured foods in certain countries
and regions of the world to allow allergic consumers to avoid them. These include molluscan shellfish, mustard, celery (root celery or celeriac) and
lupin. This review will focus on the structural
attributes and common properties of allergens and
then describe in more detail the allergens found in
more commonly important allergenic foods.

Common properties and structural
attributes of food allergens
The last 10–15 years have seen an explosion in the
number of allergenic proteins described from a vast
array of foods, which has allowed the application
of various bioinformatic tools to classify them
according to their structure and function into
protein families. Some years ago this was undertaken for both plant and animal food allergens,
together with pollen allergens. This analysis has
demonstrated that the majority of allergens in each
of these groups fell into around three to 12 families,
the remaining allergens belonging to around 14–23
families comprising one to three allergens in each.
Thus, around 65% of plant food allergens belonged
to just four protein families, known as the prolamin,
cupin, Bet v 1 and profilin superfamilies, whereas
animal-derived food allergens fall into just three
main families, namely the tropomyosins, EF-hand

Food Antigens

and caseins. A summary of the major and several
of the minor allergen families is given below.

Animal food allergen families
Tropomyosins (Fig. 2.1)
Tropomyosins are contractile proteins which,
together with the other proteins actin and myosin,
function to regulate contraction in both muscle and
non-muscle cells and are ubiquitous in animal cells.
They comprise a repetitive sequence of heptapeptide repeats that spontaneously form two strands of
α-helix which then assemble into two-stranded
coiled coils. These monomers then assemble into
head-to-tail polymers along the length of an actin
filament. These are the major allergens of two invertebrate groups, Crustacea and Mollusca, which
include the food group commonly known as shellfish. They have been identified as both food and
inhalant allergens, being characterized as allergens
in dust mite and cockroach, and consequently have
been termed invertebrate pan-allergens. IgE-epitope

2

mapping has shown that sequences unique to invertebrate tropomyosins, located in the C-terminal
region of the protein, play an important role in their
allergenic potential. Their lack of homology between
vertebrates and invertebrates means there is no
cross-reactivity between IgE from shellfish-allergic
individuals and animal muscle tropomyosins.

Parvalbumins (Fig. 2.2)
Parvalbumins represent the second-largest animal
food allergen family and are abundant in the white
muscle of many fish species, where they have a role
regulating free intracellular calcium levels, which
are important for muscle fiber relaxation. They are
ubiquitous in animals and have been classified into
two different types, α and β, which possess distinct
evolutionary lineages but are structurally very
similar. In general it is the β-parvalbumins that are
allergenic. Structurally they are characterized by a
calcium-binding motif found in many proteins,
known as an EF-hand, which comprises a 12 amino

A

B

Figure 2.1  Three-dimensional structure of tropomyosin in
insect flight muscle (PDB code 2W4U) and example of a
tropomyosin from an invertebrate which is typical of the
allergenic tropomyosins found in crustaceans and molluscs.
(a) A view along tropomyosin chains; (b) a cross-sectional view.
Tropomyosin is shown in red. Other proteins are troponin and
actin. α-Helices and loops are shown in cyan and yellow,
respectively.

Figure 2.2  Three-dimensional structure of calcium-liganded
carp parvalbumin (PDB code 4CPV, Cyp c 1). Parvalbumin has
two calcium-binding sites which have the same structural motif
formed by an α-helix linked to a second α-helix by a 12-residue
loop around the calcium cation. Calcium cations are shown as
green spheres. α-Helices are shown in cyan cylinders and loops
are shown in yellow.
17

Food Allergy

acid loop flanked on either side by a 12 residue
stretch of α-helix. Parvalbumins possess three
EF-hand motifs, two of which bind calcium, and
consequently, as with many other proteins with
integral metal ions, the loss of calcium causes a
change in protein conformation which is associated
with a loss of IgE-binding capacity. Recently a sarcoplasmic calcium-binding protein has been identified as an allergen in pacific white shrimp Litopenaeus
vannamei called Lit v 4.0101, allergenic homologs of
which can be found in other crustacean species
such as lobster. This protein also possesses an E-Fhand motif and is thought to be an invertebrate
parvalbumin, as it also functions as a calciumbuffering protein in invertebrate muscle.

Caseins (Fig. 2.3)
The major protein in milk is a fraction known as
casein which comprises a heterogeneous mixture of
structurally mobile proteins known αs1-, αs2- and
β-caseins, although the αs2-casein gene is not
expressed in humans. These proteins possess clusters of phosphoserine and/or phosphothreonine
residues which bind calcium, forming a shell
around amorphous calcium phosphate to form
microstructures called nanoclusters. This ability
allows calcium to reach levels in milk that exceed
the solubility limit of calcium phosphate. The αs1-,
αs2- and β-caseins assemble into large macro­
molecular structures known as casein micelles,

Figure 2.3  Modeled three-dimensional structure of bovine

β-casein (Bos d 8). α-Helices and loops are shown in cyan and
yellow, respectively. Structure reference: Beta-Casein variant A
structure: T. F. Kumosinski, E. M. Brown, and H. M. Farrell, Jr.,
Three-Dimensional Molecular Modeling of Bovine Caseins: An
Energy-Minimized Beta-Casein Structure (1993) Journal of Dairy
Science, 76: 931–45.
18

which are stabilized by a polypeptide chain known
as κ-casein. The α- and β-caseins are related to the
secretory calcium-binding phosphoprotein family
together with proteins involved in mineralization
and salivary proteins, whereas κ-caseins may be distantly related to fibrinogen γ-chain. There is considerable similarity in the caseins from different
mammalian milks used for human consumption,
which explains their IgE cross-reactivity.

Minor animal food allergen families
There are several less well represented animal food
allergen families which encompass ligand-binding
proteins that function as carriers, enzymes and protease inhibitors. One of the types of carrier molecule is known as the lipocalin family, a group of
diverse proteins that share about 20% sequence
identity but have a conserved three-dimensional
structure. They are characterized by a central tunnel
which can often accommodate a diversity of
lipophilic ligands, and are thought to function as
carriers of odorants, steroids, lipids and pheromones, among others. The majority of lipocalin allergens are respiratory, having been identified as the
major allergens in rodent urine, animal dander and
saliva, as well as in insects such as cockroaches,
although the only lipocalin that acts as a food allergen is the cows’ milk allergen, β-lactoglobulin.
Another carrier protein family are the transferrins,
eukaryotic sulfur-rich iron-binding glycoproteins
which function in vivo to control the level of free
iron in biological fluids.
Another minor family is the glycoside hydrolase
family 22 clan of the O-glycosyl hydrolase superfamily to which lysozyme type C and α-lactalbumins
belong, being structurally homologous despite
having very different functions, α-lactalbumin
being involved in lactose synthesis in milk, whereas
lysozyme acts as a glycohydrolase, cleaving bacterial
peptidoglycans. Furthermore, α-lactalbumin, unlike
hen’s egg lysozyme, binds calcium. A second minor
allergen family comprising enzymes are the arginine
kinases, which have been identified as allergens in
invertebrates. They belong to a family of structurally
and functionally related ATP:guanido phosphotransferases that reversibly catalyze the transfer of
phosphate between ATP and various phosphogens.
Two different types of protease inhibitor families
are also allergenic. These include the serpins, a
class of serine protease inhibitors of which some
family members have lost their inhibitory activity.

Food Antigens

A second type are the Kazal inhibitors, which also
inhibit serine proteases and can contain between 1
and 7 Kazal-type inhibitor repeats.

Plant food allergen families
Prolamins (Fig. 2.4)
The prolamin superfamily was initially identified
on the basis of a conserved pattern of cysteine
residues found in the sulfur-rich seed storage
prolamins, the α-amylase/trypsin inhibitors of
monocotyledonous cereal seeds, and the 2S storage
albumins. Subsequently other low molecular

A

2

weight allergenic proteins have been identified as
belonging to this superfamily, including soybean
hydrophobic protein, non-specific lipid transfer
proteins and α-globulins. The conserved cysteine
skeleton comprises a core of eight cysteine residues
that includes a characteristic Cys–Cys and Cys–X–
Cys motif (X representing any other residue). Two
additional cysteine residues are found in the alphaamylase/trypsin inhibitors. Apart from the seed
storage prolamins, which are characterized by
the insertion of an extensive repetitive domain,
members of this superfamily share a common
three-dimensional structure. This comprises a
bundle of four α-helices stabilized by disulfide

C

Figure 2.4  Three-dimensional structures of prolamin family

B

proteins. (a) nsLTP from wheat (PDB code 1CZ2; Tri a 14). (b) The
2S albumin from peanut (PDB code 1W2Q; Ara h 6). (c)
α-Amylase inhibitor from wheat (PDB code 1HSS). α-Helices and
loops are shown in cyan and yellow, respectively. Disulfide
bridges are shown in green ball-and-stick form.
19

Food Allergy

bonds which are arranged in such a way as to create
a lipid-binding tunnel in the nsLTPs which is collapsed in the 2S albumin structures. It is also
responsible for maintaining the three-dimensional
structure of many of these proteins even after
heating, which is associated with their retaining
their allergenic properties after cooking and may
contribute to their resistance to proteolysis.

2S albumins
A major class of seed storage proteins, the 2S
albumins are usually synthesized in the seed as
single chains of 10–15 kDa which may be posttranslationally processed to give small and large
subunits which usually remain joined by disulfide
bonds. The type of this processing depends on the
plant species,those in sunflower being single-chain
albumins and those in Brazil nut being two-chain
albumins. They can act as both occupational (sensitizing through inhalation of dusts) and food
allergens.

Lipid transfer proteins
The name of these proteins derives from the fact
they were originally identified in plants because of
their ability to transfer lipids in vitro, but their
actual biological function in plants is unclear.
Because their expression is regulated by abiotic
stress, belonging to pathogenesis-related protein
group 14, they may have a role in plant protection.
They are located in the outer epidermal tissues of
plants, such as the peel of peach or apple fruits, and
this, together with their lipid-binding characteristics, has led to the suggestion they are involved in
transporting cutin and suberin monomers to the
outer tissues of plants, where they polymerize to
form the outer waxy layers. They have been termed
pan-allergens and are the most widely distributed
type of prolamin, being found in a variety of plant
organs including seeds, fruit and vegetative tissues.
Thus, in addition to being identified in many different fruits and seeds, they have also been characterized as allergens in the pollen of several plant
species such as olive and Parietaria judaica as well
as inhalant allergens involved in occupational allergies to dusts such as wheat flour in Baker’s asthma.
The IgE cross-reactivity of LTPs from the Rosaceae
fruits has been demonstrated and related to conservation of their surface structure but to date such
cross-reactivity has not been demonstrated between
pollen and food allergens. Certainly allergy involving peach LTP Pru p 3, has been demonstrated to
20

be independent of pollen LTP sensitization and is
associated with much higher levels of peach Pru p
3 specific IgE, implying it is the primary sensitizing
agent involved in this food allergy.

Seed storage prolamins
The cysteine skeleton and α-helical structure generally characteristic of the prolamin superfamily has
been disrupted in the seed storage prolamins as a
consequence of the insertion of a repetitive domain
rich in the amino acids proline and glutamine. This
repetitive domain dominates their physicochemical
properties of the seed storage prolamins and is
thought to adopt a loose spiral structure formed
from a dynamic ensemble of unfolded and secondary structures comprising overlapping β-turns or
poly-L-proline II structures. They are the major seed
storage proteins of the related cereals wheat, barley
and rye, those from wheat being able to form large
disulfide-linked polymers that comprise the viscoelastic protein fraction known as gluten. These proteins are characteristically insoluble in dilute salt
solutions, either in the native state or after reduction of interchain disulfide bonds, being instead
soluble in aqueous alcohols.

Bifunctional inhibitors
This group of allergens are restricted to cereals, individual subunits acting as inhibitors of trypsin (and
sometimes other proteinases), α-amylases from
insects (including pests) or both,leading to their
being termed bifunctional. These proteins can have
a role as allergens in occupational allergies to wheat
flour, such as baker’s asthma, or in food sensitizing
via the gastrointestinal tract. They were initially
identified in extracts made with mixtures of chloroform and water and are often called CM proteins,
but are also soluble in water, dilute salt solutions
or mixtures of alcohol and water.

Bet v 1 homologs (see Fig. 2.7)
A very important group of allergens are those that
are homologous to the major birch pollen allergen
Bet v 1. A β-barrel protein that can bind plant steroids in a central tunnel, Bet v 1 and its homologs
belong to family 10 of the pathogenesis-related proteins and may have a role in plant protection, acting
as a steroid carrier, although this has not been
confirmed. The conservation of both primary structure (amino acid sequence) and the molecular surfaces of Bet v 1 and its homologs explains the

Food Antigens

cross-reactivity of IgE and hence the widespread
cross-reactive allergies to fresh fruits and vegetables
frequently observed in individuals with birch
pollen allergy. Two classical examples are the allergies to fruits, such as apple, and nuts, notably hazelnut. In both instances individuals tend to have
allergy to birch pollen and suffer from oral allergy
syndrome on consumption of fresh apple or hazelnuts which is associated with the presence of IgE
specific for the Bet v 1 homologues found in these
foods, known as Mal d 1 and Cor a 1 respectively.

Cupins (Fig. 2.5)
A functionally diverse protein superfamily, the
cupins have probably evolved from a prokaryotic

2

ancestor and are found in microbes and plants but
not animals. They are characterized by a β-barrel
structure from which their name is derived, ‘cupin’
meaning barrel in Latin. Using this basic structural
motif, a diverse range of biological functions have
been derived, including sporulation proteins in
fungi, sucrose-binding activities and enzymatic
activities found in germins, where manganese is
bound in the center of the barrel. In flowering
plants the cupin barrel has been duplicated to give
the bi-cupins, which include the 7S and 11S seed
storage globulins. The 11S globulins, sometimes
termed legumins, are hexameric proteins of ~300–
450 kDa. Each subunit is synthesized in the seed
as a single chain of ~60 kDa, which is posttranslationally processed to give rise to acidic
(~40 kDa) and basic (~20 kDa) chains, linked by
a single disulfide bond, and are rarely, if ever, glycosylated. The 7/8S globulins, also termed vicilins, are
somewhat simpler, comprising three subunits of
~40–80 kDa, but typically about 50 kDa.

Minor plant food allergen families
As with animal food allergens there are a number
of minor families. One of the most important
of these are the profilins (Fig. 2.6), a group of

A

B

Figure 2.5  Three-dimensional structure of native soybean

β-conglycinin trimer (PDB code 1IPK; Gly m 5). (a) The structure
consists of three chains, A, B and D. Chains are shown in
space-filling representation; (b) chain B is shown in cartoon
mode. α-Helices are shown as cyan cylinders. β-Pleated sheets
and loops are shown in magenta and yellow, respectively.

Figure 2.6  Three-dimensional structure of birch profilin (PDB
code 1CQA, Bet v 2). α-Helices are shown as cyan cylinders.
Single β-pleated sheets and loops are shown in magenta and
yellow, respectively.

21

Food Allergy

allergens involved in the pollen–fruit allergy syndrome. Cytosolic proteins found in all eukaryotic
cells, profilins are thought to regulate actin polymerization by binding to monomeric actin and a
number of other proteins. However, only profilins
found in plants, where they are highly conserved,
have been described as allergens. As a consequence,
profilin-specific IgE cross-reacts with homologs
from virtually every plant source, and sensitization
to these allergens has been considered a risk factor
for multiple pollen allergies and pollen-associated
food allergy. However, the clinical relevance of
plant food profilin-specific IgE is still under
debate.
Many of the remaining minor plant food allergen
families have a role in protecting plants from pests
and pathogens. Two types of enzyme family have
been described as plant food allergens, including
the glycoside hydrolase family 19 proteins known
as class I chitinases, which are involved in latexfood allergies, and the cysteine (C1) papain-like
proteases. Plant class I chitinases degrade chitin, a
major structural component of the exoskeleton of
insects and of the cell walls of many pathogenic
fungi, and hence have a role in protecting plants
against pests and pathogens. They possess an
N-terminal domain that is structurally homologous
with hevein, a major latex allergen, which is thought
to bind chitin. As a consequence of this homology,
class I chitinases from fruits such as avocado,
banana and chestnut have been identified as major
allergens that cross-react with IgE specific to the
latex allergen Hev b 6.02. The 43-residue polypeptide chain of hevein-like domains contains four
disulfide bonds, to which they owe their stability,
and because of their widespread occurrence in
plants have been termed pan-allergens. The cysteine
proteases, to which fruit allergens belong, notably
in kiwi, were originally characterized by having a
cysteine residue as part of their catalytic site,
although some members may have lost the capacity
to act as proteases, a notable example being the
soybean P34 protein, in which a glycine has
replaced the active site cysteine residue.
Other minor plant food allergen families include
the Kunitz/bovine pancreatic trypsin inhibitors and
some lectins. The Kunitz inhibitors are active
against serine, thiol, aspartic and subtilisin proteases, and in plants they probably play a role in
defense against pests and pathogens. They belong
to a superfamily of structurally related proteins
which share no sequence similarity and which
22

includes such diverse proteins as interleukin (IL)-1
proteins, heparin-binding growth factors (HBGF)
and histactophilin. The thaumatin-like proteins
(TLPs) are structurally similar to the intensely
sweet-tasting protein thaumatin found in the fruits
of the West African rainforest shrub Thaumatococcus
daniellii. They are also involved in plant protection,
belonging to the PR-5 family of proteins.

Common properties and
predicting allergens
What does the classification of allergens into
protein families tell us? Great efforts have been
made to use bioinformatic methods to predict what
makes some proteins allergens and not others,
especially to support the allergenic risk assessment
process for allergens in novel foods and genetically
modified organisms destined for food use. However,
it is not yet possible to predict allergenic activity in
proteins, and it is clear that membership of one of
a limited number of protein families is not in itself
sufficient to determine allergenic activity. However,
proteins from the same family often share common
properties conferred by the structural features of
that particular family. It seems that several factors
contribute to determining whether a given atopic
individual will become sensitized to a given individual. These include the genetic make-up and
atopic tendencies of the exposed individual and
factors such as the abundance of an allergen in a
food, its structure, and the biochemical and physicochemical properties of the allergen. These include
a protein’s ‘stability’, reflecting its ability to either
retain or regain its original native three-dimensional
structure following treatments such as cooking, and
to resist attack by proteases, such as those encountered in the gastrointestinal tract. Such stability has
the potential to be modified by ligands, such as
lipids and metal ions. Other factors, such as interaction with membranes, the ability to aggregate, or
the presence of repetitive structures, may also influence allergenic potential. It may also be that,
although glycans are not so important in triggering
allergic reactions in individuals once sensitized,
they may play a role in effecting sensitization in the
first place. However, an understanding of structural
relationships and common properties does help to
explain many of the cross-reactive allergies observed
and the common responses of many different types
of food allergy to processes such as cooking. The
following sections give a summary of the current

Food Antigens

knowledge of allergens in the major allergenic
foods identified to date.

Animal food allergens
Cows’ milk
Cows’ milk is an important allergenic food in early
childhood, allergies in adults being rare. Allergens
that have been identified include proteins found
in both whey and curd fractions. Major whey allergens include β-lactoglobulin (Bos d 5), the only
lipocalin that acts as a food allergen. An 18.4 kDa
protein with a lipocalin β-barrel structure, it has a
ligand-binding tunnel which can bind a variety of
lipophilic molecules, including retinoic acid and
fatty acids such as palmitate. It is stabilized by two
intramolecular disulfide bonds together with a
single free cysteine residue. The other whey protein
allergen is α-lactalbumin (Bos d 4), a calciumbinding protein that belongs to the glycoside
hydrolase family 22 clan. It has a superimposable
three-dimensional structure with the egg allergen
lysozyme. A 14.2 kDa calcium-binding protein,
α-lactalbumin is stabilized by four disulfide bridges
and has a role in regulating lactose synthase. Its
three-dimensional structure is primarily α-helical
in nature, with some 310 helix and β-sheet the parts
of the polypeptide which form the calcium-binding
site being the most ordered (less mobile, more
rigid) part of the protein structure.
In addition to the whey proteins, the major allergens of cows’ milk are the caseins (Bos d 8), a
heterogeneous mixture of proteins called αs1-, αs2and β-caseins which are produced by a polymorphic
multigene family and undergo post-translational
proteolysis and phosphorylation. Other minor
allergens identified in milk include the iron-binding
protein lactoferrin, serum albumin (Bos d 6) and
immunoglobulin (Bos d 7). IgE cross-reactivity
studies in a group of cows’ milk-allergic infants
showed that although all but 10% had serum IgE
against αs2-casein, only around half recognized αs1casein, and only a small proportion (15%) had IgE
against β-casein. The high level of homology (e.g.
>90%) between whey proteins and caseins from
different mammalian species explains the extensive
IgE cross-reactivity observed between the milks of
cow, sheep and goat, individuals with cows’ milk
allergy generally reacting when undergoing oral
challenge with goats’ milk; allergies to goats’ or

2

sheep’s milk have been emerging, although the IgE
reactivity seems to be limited to the casein fraction.
Reduced IgE cross-reactivity has been observed with
mares’ milk proteins, such that some individuals
with cows’ milk allergy can tolerate mares’ milk, and
there are indications that camels’ milk also has a
reduced IgE cross-reactivity compared with cow’s
milk. Such observations have led to the suggestion
that milk from mammals such as horse, donkey and
camel might have some utility as a substitute for
cows’ milk suitable for consumption by cows milk
allergic individuals, be used in selected cases of
cows’ milk allergy, once they have been processed
to make them suitable for consumption by human
infants.
Food processing procedures can result in further
modification of cows’ milk proteins, with pasteurization resulting in β-lactoglobulin becoming covalently attached to casein micelles and thermal
treatments, in particular spray drying, resulting in
extensive lactosylation. Thus, the allergenic activity
of β-lactoglobulin has been found to increase 100fold following heating in the presence of lactose,
whereas severe thermal processing, such as baking,
appears to reduce the allergenicity of milk compared to less severe heat treatments. Both whey
proteins form thermally induced aggregated structures and at high protein concentrations form
gelled networks, whereas caseins can have a tendency to aggregate. Both α-lactalbumin and the
caseins are highly susceptible to digestion by
pepsin, being rapidly degraded. In the case of
α-lactalbumin this may relate to the pH-labile
nature of the allergen, which unfolds at low pH,
whereas the caseins, as mobile proteins, are excellent substrates for pepsin. These properties contrast
with those of β-lactoglobulin, which is resistant to
pepsin at physiological concentrations and is
digested only slowly by the duodenal endoproteases trypsin and chymotrypsin. Processing may
modify their susceptibility to digestion, and
although thermal denaturation enhances the digestability of β-lactoglobulin it does not affect the susceptibility of caseins to digestion. However,
interaction with other food components and food
matrices can have unexpected effects. Thus, adsorption to oil droplets increases the susceptibility of
β-lactoglobulin to pepsinolysis, whereas adsorption of β-casein results in certain fragments being
protected from pepsinolysis, including regions
spanning known IgE epitopes. Such effects of
processing may underlie the differences in clinical
23

Food Allergy

reactivity of baked milk foods, compared to less
extensively thermally processed milk products.

Egg
A second important allergenic food of infancy and
childhood is egg, for which a number of allergens
have been identified. These include the dominant
hen’s egg-white allergen Gal d 1, the extensively
glycosylated Kazal inhibitor (comprising three
Kazal-like inhibitory domains) known as ovomucoid, and the serpin serine protease inhibitor ovalbumin, Gal d 3. It is ovomucoid that is responsible
for the viscous properties of egg white, whereas
ovalbumin accounts for more than half the protein
in egg white. Gal d 1 comprises three tandem
domains (Gal d 1.1, Gal d 1.2, Gal d 1.3) stabilized
by intradomain disulfide bonds, the Gal d 1.1 and
Gal d 1.2 domains possessing two carbohydrate
chains each, whereas around only half the Gal d 1.3
domains are glycosylated. Such extensive glycosylation acts to stabilize the protein against proteolysis.
Two other proteins are minor allergens which are
also homologs of cows’ milk allergens. One is lysozyme, also known as Gal d 4, a glycosidase belonging to the glycoside hydrolase family 22 clan of the
O-glycosyl hydrolase superfamily, and is homologous to cows’ milk α-lactalbumin (Bos d 4). A
second is the sulfur-rich iron-binding glycoprotein
ovotransferrin, which is homologous to the cows’
milk allergen lactoferrin. Although the major egg
allergens are found in egg white, there are indications that certain yolk proteins may also act as allergens. Thus, the egg yolk protein α-livetin has been
designated the allergen Gal d 5, and recently the
vitellogenin-1 precursor has been identified as a
minor allergen and termed Gal d 6.
It has been shown that the egg white allergen
ovomucoid becomes disulfide linked to the gluten
proteins during baking, with a concomitant reduction in the allergenic activity of soluble extracts.
These effects are apparent even following kneading.
During storage of eggs ovalbumin is transformed
into a more thermostable form known as Sovalbumin, which denatures at 88° rather than
the 80°C characteristic of the native protein. The
conversion involves conformational changes rather
than proteolysis and is the result of elevation of the
egg’s pH, with typically about 80% of the ovalbumin being converted into the S form on storage at
20°C for a month. Nothing is known about the
impact of such changes on the allergenicity of this
24

protein. Both ovalbumin and ovomucoid can be
readily digested by pepsin, but it appears that
peptide fragments of ovomucoid can retain their
IgE-binding capacity, albeit in a patient-dependent
manner. It maybe that those individuals likely to
retain their egg allergy beyond childhood show IgE
reactivity towards digestion-resistant fragments,
whereas those who outgrow their allergy have IgE
responses only to the intact protein. Ovalbumin
and lyoszyme are often used as fining agents in
wine production, but evidence to date suggests they
lose their allergenic activity when used in this way.

Fish
One of the first fish allergens to be described was
the allergenic parvalbumin of cod, Gad c 1, but a
number have now been identified in many different
fish species and can therefore be considered to be
the pan-allergens in fish. Clinical cross-reactivity to
multiple fish in individuals with allergy based on
the major fish allergen parvalbumin is a common
observation. This can be explained by the structural
similarity of the parvalbumins from various fish
species, although their lower levels in the dark
muscle of some fish species, such as tuna, may
mean they are less problematic allergens in such
types of fish. Similarly, the cross-reactivity of fish
and frog muscle in fish-allergic individuals can be
explained by the structural similarities between
their parvalbumins, although intriguingly one of
the allergens in frog is an α-parvalbumin.
One of the first records in the literature of processing affecting allergenicity is the report of Prausnitz
on the sensitivity of Kustner towards cooked, but
not raw, fish. However, it has rarely been reported
in the literature that food processing increases allergenic activity. In general it seems that fish allergens
are stable to cooking procedures, the parvalbumins
being generally resistant to heat and proteolysis. A
likely explanation for this observation is that the
E-F-hand structure of parvalbumin, whilst unfolding at elevated temperatures is able to refold on
cooling, providing calcium is still present, thus
regaining its native, IgE-reactive conformation. Such
thermostability undoubtedly contributes to the
ability of this major fish allergen to retain its allergenic properties after cooking, although the severe
heat treatment does have an effect, the IgE-binding
activity of canned fish having been estimated to be
100–200 times lower than that of boiled fish.
Thermal treatment of fish results in the formation

Food Antigens

of parvalbumin oligomers, which are generally associated with a loss of IgE-binding capacity, whereas
processes such as smoking appear to potentially
increase allergenicity and may result in the formation of novel allergens.

Molluscan and crustacean Shellfish
Members of a family of closely related proteins
present in muscle and non-muscle cells, tropomyosins are major seafood allergens found in various
species of Crustacea, including shrimp, crab and
lobster, as well as Mollusca, such as abalone,
mussels, squid and octopus. First characterized as
allergens in shrimp, tropomyosins are now acknowledged to be invertebrate pan-allergens. To date, all
allergenic tropomyosins have been confined to vertebrates and invertebrates and are highly homologous to non-allergenic forms from invertebrate
species, sequence differences being confined to the
first two residues of the IgE epitope in the C-terminal
portion of the protein, which is crucial for IgE
binding. The uniqueness of this region to invertebrate tropomyosins explains the lack of IgE crossreactivity between shellfish and animal muscle
tropomyosins. Recently efforts to exploit this similarity in order to graft ‘allergenic’ invertebrate tropomyosin epitopes onto the human tropomyosin
scaffold have shown that conformational epitopes
play a major role in the allergenicity of tropomyosin, which cannot be identified using short synthetic peptides. The extensive homologies between
allergenic tropomyosins result in IgE cross-reactivity,
individuals sensitized to tropomyosin from one
particular crustacean species often showing IgE
cross-reactivity, which is often (although not always)
accompanied by clinical allergy to many crustacean
species. However, such extensive cross-reactivity is
less clear with regard to mollusc reactivity, which
may be restricted to cross-sensitization. The field of
crustacean and molluscan shellfish allergies is made
complex by the diverse range of shellfish species
that humans consume, which are often described
using broad terms such as “shrimp” or “seafood”. It
is important to make distinctions between crustacean and molluscan shellfish but further research is
needed to gain the evidence currently lacking to
further classify crustacean shellfish allergies on the
basis of, for example, allergens from fresh- or marine
species or differences in IgE reactivity to the fastcompared to slow-muscle tropomyosins. A minor
group of allergens identified in shrimp are the

2

arginine kinases, which have also been identified as
cross-reactive allergens in the Indian meal moth,
king prawn, lobster and mussel. Other shrimp allergens include a sarcoplasmic calcium-binding
protein, triosephosphate isomerase (TIM), and
several contractile proteins including myosin light
chains, troponin C and troponin I. The proteins
appear to be generally heat stable, their allergenicity
being unaltered by boiling. Tropomyosins have
been detected in the cooking water, but in general
there have been few studies on the impact of cooking
on shellfish and crustacean allergenicity.

Plant food allergens
Fresh fruits and vegetables
Many allergens in fresh fruits and vegetables are
related to inhalant allergens, particularly those
found in birch pollen and latex. It is thought that
individuals initially become sensitized to the
inhalant allergens in pollen and latex and subsequently develop allergies to a variety of fresh fruits,
vegetables, nuts and seeds, because the close structural resemblance of inhalant allergens and their
homologs in foods allows IgE developed to the
inhalant allergens to bind (or cross-react) with
homologs found in foods. In addition, it appears
that some fruit and vegetable allergens can sensitize
individuals directly.
A large number of allergenic homologs of Bet v
1 have been identified in a variety of fruits and
vegetables involved in pollen–fruit cross-reactive
allergies, with perhaps the most important including the Rosacea fruits such as apple (Mal d 1),
cherry (Pru av 1) and peach (Pru p 1). They have
also been identified as allergens in emerging
allergenic foods, such as kiwi fruit (Act d 8) and
exotic fruits such as jackfruit and Sharon fruit. In
addition, allergenic Bet v 1 homologs have also
been identified in vegetables, notably celery (Api g
1) and carrot (Dau c 1) (Fig. 2.7). A second group
of IgE-cross-reactive allergens originally identified
in connection with birch pollen allergy are the profilins, and as with Bet v 1, a wide range of homologs
of the allergenic profiling in birch and other allergenic pollens have been identified in a variety of
fruits and vegetables. Many of the foods that contain
allergenic Bet v 1 homologs also contain allergenic
profilins. There have been concerns that although
profilins can sensitize individuals, the resulting IgE
25

Food Allergy

Figure 2.7  Three-dimensional structure of major carrot
allergen Dau c 1 from the Bet v 1 family of allergens (PDB code
2WQL). The structure is complexed with polyethylene glycol
oligomer. α-Helices are shown as cyan cylinders. Single
β-pleated sheets and loops are shown in magenta and yellow,
respectively.

lacks biological activity and does not play a role in
the development of allergic reactions, but this does
not seem to be a general rule and in certain patients
they may be able to trigger an allergic reaction.
Another type of allergy to fresh fruits and vegetables found in Europe appears to be generally confined to the Mediterranean area and does not seem
to be associated with prior sensitization to other
agents such as pollen. Unlike the birch pollen allergies it tends to be manifested with much more
severe, even life-threatening allergic reactions and
involves a different group of allergens, known as
the non-specific lipid transfer proteins (LTPs).
These have emerged as important allergens because
of their role in causing severe allergies to peach (Pru
p 3), and subsequently have been termed panallergens, with cross-reactive homologs having
been found in other fruits such as apple (Mal d 3)
and grape (Vit v 1), together with vegetables such
as asparagus, cabbage (Bra o 3) and lettuce. It is not
clear whether peach is the initial sensitizing allergen and that other allergies to fruits develop as a
26

consequence of IgE-cross-reactivity, in a manner
akin to the development of Bet v 1 -related allergies
(see above); whether each different type of LTP is
able to sensitize via the gastrointestinal tract; or
whether there is a ‘missing’ inhalant allergen, such
as another LTP in pollen.
A third group of relevant fruit allergens are those
involved in the latex–fruit cross-reactive allergy syndrome, which include the class I chitinases. Several
allergens have been described from a variety of
plant foods, including avocado (Pers a 1), banana
(Mus p 1.2) and chestnut (Cas s 1). Other allergens
involved in IgE cross-reactive allergies between
foods and latex include patatin, a storage protein
from potato that has also been shown to be crossreactive with the latex allergen Hev b 7, along with
other proteins from avocado and banana. Efforts to
reduce the burden of latex allergy by, for example,
reducing the use of powdered latex gloves by health
professionals in particular, may ultimately reduce
the prevalence of such latex-related food allergies,
although this will need verifying in future.
An increasingly important allergenic fruit is kiwi,
which contains several representatives of minor
plant food allergen families, including a thaumatinlike protein (TLP, Act d 2), and a thiol protease,
actinidin (Act c 1), together with allergens such as
kiwellin. Other less widely found fruit and vegetable allergens include germin-like proteins, which
have been identified as allergens in bell pepper and
orange pips (Cit s 1) and for which the N-linked
glycans have been found to be important for IgE
binding. Fruit seed storage proteins corresponding
to the 7S and 11S seed storage globulins have also
been identified as allergens in tomato. Another type
of allergen identified in celery root is the flavin
adenine dinucleotide (FAD)-containing oxidase
(Api g 5), a 53–57 kDa protein which is extensively
glycosylated, posesses cross-reactive glycans and,
albeit able to bind IgE, does not seem to be able to
stimulate histamine release.
As the major allergens are pathogenesis-related
proteins, their level of expression changes in plants
in response to abiotic stress and pathogen attack,
and changes during the process of fruit ripening
and post-harvest storage. Thus, the levels of LTP
allergens in fruit such as apple (Mal d 3) tend to be
higher in freshly picked fruit but decrease during
storage, whereas the levels of Bet v 1 homologs
(Mal d 1) tend to be lower in freshly picked apples
and to increase following modified-atmosphere
storage for several months. Processing also affects

Food Antigens

the allergenic properties of allergens in fruits and
vegetables in different ways, and it seems that different fruit tissues may respond in different fashions. Thus, for allergens such as Bet v 1 homologs,
for which the IgE-binding sites are generally conformational in nature, processing procedures that
denature this protein generally result in a loss of
IgE reactivity, and this is particularly true of fresh
fruits, although the allergenic Bet v 1 homolog
from celeriac seems to retain its allergenic activity
after thermal processing. The Bet v 1 homologs also
tend to be labile to gastrointestinal digestion,
although there are suggestions that whereas IgE
epitopes may be destroyed, the short peptides
resulting from gastrointestinal digestion maybe
able to act as T-cell epitopes and hence may modulate immune responses, even if not involved in
elicitation.
In contrast, allergens from the prolamin superfamily appear to be both resistant to thermal
processing procedures and highly resistant to gastric
and duodenal digestion. Notable among these are
the LTPs, which are generally highly resistant to
both gastric and duodenal proteases, and it seems
likely that they survive digestion in a virtually intact
form, a property that has been associated with their
allergenic potency. They also resist thermal denaturation, often refolding on cooling, and have been
found in fermented foods and beverages such as
beer (where they make an important contribution
to foam stability) and wines, although combinations of low pH and heating may be sufficient to
denature the protein. Similarly, TLPs appear to be
stable to thermal processing, being found even in
highly processed products such as wine, and being
highly resistant to simulated gastrointestinal digestion. Thus the allergenic TLP from kiwi fruit is
highly resistant to simulated gastrointestinal proteolysis, and the stability of TLPs to food processing
is shown by the presence of allergenic grape TLPs
surviving the vinification process and being found
in wine. It is likely that the rigidity of the protein
scaffold introduced by intramolecular disulfide
bonds is responsible for the stability of allergens
such as LTPs, and TLPs are probably reponsible for
their stability to proteolysis. Similarly, the intramolecular disulfide bonds in the chitin-binding
domain class I chitinases may confer stability,
although the allergenic homolog from avocado,
Pers a 1, is extensively degraded when subjected to
simulated gastric fluid digestion. However, the
resulting peptides, particularly those corresponding

2

to the hevein-like domain, were clearly reactive
both in vitro and in vivo.

Tree nuts and seeds
The major allergens of tree nuts and seeds include
other members of the prolamin superfamily, the 2S
albumins and the cupin seed globulins, both of
which often function as a protein store in the seed.
2S albumins have been identified as important
allergens in nuts, including walnut allergen (Jug r
1), almond, Brazil nut (Ber e 1), hazelnut and pistachio (Pis v 1) and in seeds such as oriental and
yellow mustard (Bra j 1) and (Sin a 1), Ses i 1 and
2 from sesame, and the 2S albumin from sunflower
seeds (SFA-8). These allergens seem to be highly
potent and may well dominate allergic responses to
many nuts and seeds. In addition to the 2S albumins, a second major group of allergens found in
nuts and seeds are the 11S and 7S seed storage
globulins that belong to the cupin superfamily.
Seed storage protein allergens have been described
in a variety of nuts and seeds, with both 11S and 7S
seed storage globulins having been reported as
allergens in hazelnut (Cor a 11 [7S globulin] and
Cor a 9 [11S globulin]), cashew nut (Ana o 1 and
Ana o 2) pistachio (Pis v 2 and Pis v 3), walnut (Jug
r 2 and Jug r 4), and sesame seed (Ses i 1, Ses i 6).
The 11S globulins have also been shown to be allergens in almond, also known as almond major
protein (AMP) and mustard (Sin a 2). The close
botanical relatedness of species such as cashew and
pistachio and the high levels of homology between
the major allergens in these tree nuts explain the
cross-reactive nature of allergies to these nuts. There
are suggestions that conformational epitopes exist
in these proteins, which are also responsible for IgE
cross-reactivity between allergens from species
where homologies are weaker. However, it is difficult to distinguish between polysensitization and
cross-reactivity.
In addition to the pollen–fruit cross-reactive
allergy syndromes, it is emerging that Bet v 1
homologs in various nuts and seeds can cause
similar allergies. These have been especially well
documented for hazelnut, where an isoform, Cor a
1.04, has been identified which resembles Bet v 1
more closely than the allergenic Bet v 1 homolog
from hazelnut pollen (Cor a 1.01). There are also
reports of LTPs found in nuts and seeds triggering
allergies similar to those observed in fruits such as
peach, including LTP allergens from walnut (Jug r
27

Food Allergy

3) and hazelnut (Cor a 8), the latter having recently
been shown to be an allergen in a population from
Northern Europe.
Another group of potentially important allergens
that have been identified in the last few years are
the oleosins, a group of proteins associated with oil
bodies, where they play an important role in packaging and stabilizing the oil droplet surface, having
a portion of the protein structure buried in the oil
phase and a second domain on the aqueous facing
surface. These have been identified as allergens in
sesame and hazelnut. The effects of cooking and
food processing tend to mirror those observed for
fruit and legume allergies, with, in general, cooking
reducing the reactivity of Bet v 1 type allergens but
having much less of an effect on allergens from the
prolamin superfamily, such as LTPs and 2S
albumins.

Legumes, including peanut
Many of the allergen types found in other plant
foods have also been identified in allergenic
legumes. They include allergenic homologs of the
cupins, with both the 7S and 11S seed storage globulins having been identified in peanut, and are
known as Ara h 1 (conarachin) and Ara h 3 (arachin),
respectively. Ara h 1 is N-glycosylated during synthesis in the peanut seed and is recognized by IgE from
individuals with glycan-reactive IgE, but it is thought
that this is not clinically significant in eliciting an
allergic reaction. Although generally thought to be
less of a problematic allergenic food than peanut,
similar allergens are found in soybean, with the 7S
globulin β-conglycinin and 11S globulin glycinin
being termed allergens Gly m 5 and 6, and appearing to be markers of more severe allergy to soybean,
although in this study the majority of individuals
with soybean allergy also had allergy to peanut.
The most potent allergen in peanuts is the
prolamin superfamily 2S albumin, Ara h 2, 6 and
7, respectively. Intriguingly, although 2S albumins
are found in soybean, they do not appear to be
major allergens in this legume. Allergenic seed
storage proteins have been identified as allergens in
lentil (Len c 1) and pea (Pis s 1), which can be
cross-reactive with peanut. Such cross-reactivity is
particularly problematic with lupin, with both the
7S and the 11S seed storage globulins, known as
β-conglutin and α-conglutin, respectively, having
been identified as allergens, lupin β-conglutin (Lup
an 1) having been designated the major allergen.
28

Both proteins have significant homology to the
peanut allergens Ara h 1 and Ara h 3 4, explaining
the clinical cross-reactivity observed between these
two legumes.
Bet v 1 homologs and profilins involved in the
cross-reactive pollen syndromes have been identified in a number of legumes, the most important
being the peanut Bet v 1 homologs known as Ara
h 8, along with peanut profiling. The Bet v 1
homolog from soybean, known as Gly m 4, albeit
more generally associated with mild symptoms, can
occasionally be associated with particularly severe
reactions, the differences in potency possibly being
explained in part, at least, by the extent of food
processing.
Other allergens identified in peanut include an
oleosin and a lectin, peanut agglutinin. Several
other soybean allergens have been described including a Kunitz trypsin inhibitor and a member of the
cysteine protease family, the 34 kD so-called oil
body-associated protein, known as Gly m 1, and
Glym Bd 30 k. Another soybean allergen which is
of relevance in countries such as Japan is the 23 kDa
protein known as Gly m 28 k, which is glycosylated
and contains important IgE-reactive glycans also
found in a derived 23 kDa peptide.
In general, the vicilin-like and legumin-like seed
globulins both exhibit a high degree of thermostability, requiring temperatures in excess of 70°C for
denaturation. The globulins have a high propensity
to form large aggregates on heating, which is widely
exploited in legume food ingredients such as flours
and isolates, to generate a diverse range of foods.
These aggregated protein structures appear to a
large degree to retain, their native secondary structures. The allergenic 2S albumin allergens are even
more thermostable than the globulin allergens. A
consequence of so many thermostable allergens is
that legumes retain their allergenicity after cooking,
and it appears that, for peanut at least, modification
by sugars to produce Maillard adducts may even
enhance the allergenic potential of peanut allergens. However, processes such as boiling result in
the loss of globulins from peanuts and lentils into
the cooking water, and may in part account for
observations that boiled peanuts appear less allergenic than their roasted counterparts.
Despite such thermostability, the 7S globulins are
highly susceptible to pepsinolysis, although several
lower molecular weight polypeptides seem to
persist following digestion of the peanut 7S globulin allergen Ara h 1, and there is evidence they still

Food Antigens

possess IgE-binding sites following proteolysis.
Similarly, in vitro simulated gastrointestinal digestion results in rapid and almost complete degradation of the protein to relatively small polypeptides,
although these retain their allergenic properties.
There are indications that the peptides do not
remain monomeric but can assemble into larger
structures, and it may be that this propensity to
aggregate is responsible for the protein retaining its
allergenic properties even when hydrolyzed. In contrast, the 2S albumins, like the structurally related
LTPs, are relatively resistant to simulated gastrointestinal proteolysis. Such factors may account for
the allergenic potency of these prolamin superfamily members.

Cereals
In addition to triggering the gluten-induced enteropathy celiac disease, wheat and other cereals can
trigger IgE-mediated allergies, although the condition is as widespread as allergies to foods such as
egg and peanut, despite a public perception that
wheat allergy is prominent. Cereals, and in particular wheat, can trigger allergic conditions such as
atopic dermatitis and exercise-induced anaphylaxis
(EIA), where patients only experience an allergic
reaction on exercising within a certain interval after
eating a problem food.
The main seed storage proteins of cereals, known
as seed storage prolamins, are highly heterogeneous, and in wheat comprise a mixture of 60–100
polypeptides. They have the relic of the conserved
disulfide skeleton of the prolamin superfamily into
which a repetitive domain of variable length, composed largely of glutamine and proline residues, has
been inserted. The proteins are characteristically
soluble in aqueous alcohols and include two major
fractions, the monomeric gliadins soluble in dilute
acetic acid or 70% (v/v) ethanol, and polymeric
glutenins, which require the presence of reducing
agent and 25% propanol for solubility. This lack of
solubility in dilute salt solutions, such as those commonly used in clinical diagnostics, makes the diagnosis of wheat and cereal allergies more complicated
and may mean that such allergies go undiagnosed
or even missed. A number of prolamin allergens
have been described, including the monomeric γ-,
α- and ω-5 gliadins and the polymeric high molecular weight and low molecular weight subunits of
glutenin. Of these, the ω-5 gliadin has been
described as being a marker for more severe

2

exercise-induced allergic reactions to wheat. As well
as the poorly soluble seed storage prolamins, the
water- and salt-soluble albumins and globulins can
also act as allergens, notably other members of the
prolamin superfamily. Thus, several different forms
of the cereal trypsin/α-amylase family have been
identified as inhalant and food allergens in wheat
and other cereal foods such as rice. Furthermore,
the LTPs have been described as allergens in foods
such as maize, spelt and wheat (Tri a 14).
Cooking appears to affect the allergenicity of all
the cereal allergens, and it has been suggested that
baking may be essential for the allergenicity of
cereal prolamins with indications being that IgE
binding proteins in cereals resist digestion to a
greater extent after baking. There do appear to be
differences in the responsiveness of allergens to
cooking by the same protein from different plant
species. Thus, wheat LTP unfolds at a slightly lower
temperature than maize LTP (60° as opposed to
75°C), and cooking reduces the IgE-binding capacity of wheat LTP in some patients and not others.
In contrast, maize LTP appears highly resistant, its
allergenic activity being unaffected by cooking, like
that of the α-amylase inhibitors. It is interesting to
note that barley LTP, which is structurally closer to
wheat than maize LTP, unfolds following extensive
heating such as is employed in wort boiling, but
that on cooling a proportion remains irreversibly
denatured, the remainder refolding to the native
structure. This may explain why some individuals
react to LTP remaining in beer after brewing, where
it probably plays an important role in foam
stabilization.

Allergens in diagnosis and treatment
of food allergies
Currently the gold standard for diagnosis of food
allergy remains double blind placebo controlled
food challenge, although frequently diagnosis is
performed based on clinical history together with
food specific serum IgE and/or a positive skin prick
test. Whilst easier to perform these tests currently
only assess whether an individual is sensitised (i.e.
have food specific IgE) but it is known that many
of these individuals do not necessarily express a
clinical reaction on exposure to the food they are
sensitised to – often in up to 50% of cases. One way
of improving the specificity and sensitivity of in
vitro diagnostics, such as serum IgE tests, maybe to
29

Food Allergy

use individual purified allergens rather than relying
on crude food extracts. This has given rise to the
term component resolved diagnosis, with purified
authenticated allergens being used either in classical formats, such as the ImmunoCAP, or more
recently using microarray technology where minute
quantities of individual allergens are spotted onto
a solid support – often a glass slide. Such “chip”
based diagnostics have advantages in using relatively small volumes of serum but provide a much
more complex readout for the clinician to understand. For example, given the IgE cross-reactivity of
allergenic parvalbumins from many fish species, is
it sufficient to test only for IgE towards one representative parvalbumin molecule such as Gad c 1?
Similarly could a representative shellfish allergen,
such as the tropomyosin allergen Pen a 1 provide
diagnosis for all crustacean shellfish allergies? There
are indications that sensitisation to tropomyosin is
an effective marker of shrimp allergy and may offer
superior diagnostic efficiency compared to total
shrimp IgE and skin testing. However, whether tropomyosin from one shrimp species can be used as
a diagnostic marker for allergy to either all crustacean species and/or molluscan shellfish allergy,
remains to be proven. It is also emerging that the
peanut 2S albumin allergens Ara h 2 and Ara h 6
are important indicators of clinical allergy to
peanut. The patterns of reactivity to particular molecules can show a geographic distribution and has
been well characterised for allergies to fruit such as
apple for which Bet v 1 homologue sensitisation
appears to dominate in Northern Europe whilst LTP
sensitisation being more relevant in the Mediterranean area. This may mean that component
resolved approaches need to take account of such
factors, and whilst sensitisation to the LTP allergen
from peach, Pru p 3, is highly likely to have a diagnostic utility in Mediterranean populations, its
usefulness remains to be established in other
populations where the relationship between sensitisation to LTP and clinical allergy remains to be
defined. Thus, component resolved approaches
have great potential to improve diagnosis of allergy
but are in their infancy and require further validation to assess the robustness and utility in different
populations.
In addition to improving the sensitivity and specificity of in vitro diagnostics for food allergy, our
greater knowledge of allergens is also being used to
improve the treatment of food allergy. Currently
the major treatment for food allergy involves
30

individuals avoiding their problem food, and for
those with a history of severe allergies, they are
equipped with rescue medication in case of accidental exposure. As a consequence of societies
increasing reliance on prepackaged and processed
foods, allergenic ingredients may not always been
apparent, making reading of food labels a way of
life for food allergic consumers. However, these
strategies can fail, and as a result food allergy is a
significant cause of anaphylaxis, one of the main
causes of emergency admissions to hospital, and
which can result in fatalities. To date the most effective treatment which comes closest to a cure is
allergen-specific immunotherapy (SIT) but it has
not been successfully applied to food allergy
because anaphylactic side-effects are too numerous
and severe. One strategy which is now being applied
to improve the utility of SIT for food allergy is
modify the allergen in such way that its decreased
IgE-binding capacity, and hence its potency to
elicit and allergic reaction, is significantly, reduced.
Through a knowledge of the molecular basis of
allergenic activity allergenic molecules are being
redesigned to retain their immunological activity at
the level of the T-cell (and hence retain their capacity to desensitise and individual) whilst reducing
adverse reactions by modiying their IgE-epitopes.
Some examples where this has been attempted are
the humanization of the tropomyosin from shrimp,
known as Pen a 1 and produce mutant fish parvalbumin molecules which are hypoallergenic yet may
retain their ability to desensitise.

Conclusion
The last decade has seen a rapid increase in our
knowledge of the molecules in foods that cause and
trigger allergic reactions. They appear to be restricted
to a small number of protein families, but we still
do not understand why certain protein and protein
scaffolds dominate the landscape of allergen structures. Indications are that the relationships between
protein structure and allergenicity are very subtle,
and for food proteins are further complicated by
relatively poorly understood processing-induced
changes. Such effects may modulate the allergenicity of food proteins, and may either reduce or
increase the allergenic activity of individual molecules, different protein structures responding in different ways. Investigating the factors that modulate
the allergenicity of proteins is a research challenge

Food Antigens

for the coming years, and will require studies on
allergen structure and properties to be linked with
studies in animal models and clinical research. This
is important if we are to realize the potential of new
diagnostic approaches, such as component resolved
diagnosis, as well as identifying processing strategies and novel processing techniques that may
reduce the allergenicity of foods. It will also require
clinicians and allied health professionals to have a
deeper knowledge of the impact food-processing
procedures may have on the allergenicity of foods,
and the molecules responsible for them. Such
knowledge will enable health professionals to
provide patients with the knowledge they need to
avoid problems foods effectively.

Bibliography
General references about allergens
and allergen structure
Breiteneder H, Mills ENC. Molecular properties of food
allergens. J Allergy Clin Immunol 2005;115:14–23;
quiz 24.
Radauer C, Bublin M, Wagner S, et al. Allergens are
distributed into few protein families and possess a
restricted number of biochemical functions. J Allergy
Clin Immunol 2008;121(4):847–52.
Chapman MD, Pomés A, Breiteneder H, et al.
Nomenclature and structural biology of allergens.
J Allergy Clin Immunol 2007;119(2):414–20.
EFSA Panel on Genetically Modified Organisms (GMO).
Scientific Opinion on the assessment of allergenicity of
GM plants and microorganisms and derived food and
feed. EFSA Journal 2010;8(7):1700. [168 pp.].
doi:10.2903/j.efsa.2010.1700.
Salcedo G, Sánchez-Monge R, Barber D, et al. Plant
non-specific lipid transfer proteins: an interface
between plant defence and human allergy. Biochim
Biophys Acta 2007;1771(6):781–91.
Mills EN, Jenkins J, Marigheto N, et al. Allergens of the
cupin superfamily. Biochem Soc Trans 2002;30(Pt
6):925–9.
Fötisch K, Vieths S. N- and O-linked oligosaccharides of
allergenic glycoproteins. Glycoconj J 2001;18:373–90.

2

Nowak-Wegrzyn A, Fiocchi A. Rare, medium, or well done?
The effect of heating and food matrix on food protein
allergenicity. Curr Opin Allergy Clin Immunol 2009;
9(3):234–7.

Animal food allergens
Cow’s milk:
Wal JM. Structure and function of milk allergens. Allergy
2001;56(Suppl 67):35–8.

Egg:
Mine Y, Yang M. Recent advances in the understanding
of egg allergens: basic, industrial, and clinical
perspectives. J Agric Food Chem 2008;56(13):
4874–900.

Fish and Shellfish:
Lopata AL, Lehrer SB. New insights into seafood allergy.
Curr Opin Allergy Clin Immunol 2009;9(3):270–7.
Lopata AL, O’Hehir RE, Lehrer SB. Shellfish allergy. Clin
Exp Allergy 2010;(6):850–8.
Taylor SL. Molluscan shellfish allergy. Adv Food Nutr Res
2008;54:139–77.

Plant food allergens
Fresh fruits and vegetables:
Egger M, Mutschlechner S, Wopfner N, et al. Pollen-food
syndromes associated with weed pollinosis: an update
from the molecular point of view. Allergy 2006;61(4):
461–76.
Fernández-Rivas M, Benito C, González-Mancebo E, et al.
Allergies to fruits and vegetables. Pediatr Allergy
Immunol 2008;19(8):675–81.

Peanut, Soybean and other legumes
L’Hocine L, Boye JI. Allergenicity of soybean: new
developments in identification of allergenic proteins,
cross-reactivities and hypoallergenization technologies.
Crit Rev Food Sci Nutr 2007;47(2):127–43.

Tree nuts:

Effects of food processing
on allergens

Roux KH, Teuber SS, Sathe SK. Tree nut allergens. Int Arch
Allergy Immunol 2003;131(4):234–44.

Mills ENC, Sancho AI, Rigby NM, et al. Impact of food
processing on the structural and allergenic properties
of food allergens. Mol Nutr Food Res 2009;53(8):
963–9.
Maleki SJ, Hurlburt BK. Structural and functional
alterations in major peanut allergens caused by
thermal processing. J AOAC Int 2004;87(6):1475–9.

Wheat:
Battais F, Richard C, Jacquenet S, et al. Wheat grain
allergies: an update on wheat allergens. Eur Ann
Allergy Clin Immunol 2008;40(3):67–76.
Tatham AS, Shewry PR. Allergens to wheat and related
cereals. Clin Exp Allergy 2008;38(11):1712–26.
31

Food Allergy

Allergens in diagnosis and treatment
of food allergies
Sommergruber K, Mills ENC, Vieths S. Coordinated and
standardized production, purification and
characterization of natural and recombinant food
allergens to establish a food allergen library. Mol Nutr
Food Res 2008;52(S2):S159–S165.
Asero R, Ballmer-Weber BK, Beyer K, et al. IgE-mediated
food allergy diagnosis: Current status and new
perspectives. Mol Nutr Food Res 2007 Jan;51(1):
135–47.
Sastre J. Molecular diagnosis in allergy. Clin Exp Allergy
2010;40(10):1442–60.

32

Valenta R, Linhart B, Swoboda I, et al. Recombinant
allergens for allergen-specific immunotherapy: 10 years
anniversary of immunotherapy with recombinant
allergens. Allergy 2011 Feb 26. doi: 10.1111/
j.1398-9995.2011.02565.x

Further reading
Mills ENC, Shewry PR, editors. Plant Food Allergens.
Oxford: Blackwells; 2003. p. 219.
Mills ENC, Wichers H, Hoffman-Sommergruber, K, editors.
Managing Allergens in Foods. Cambridge UK:
Woodhead Publishing; 2007. p. 315.

CHAPTER

3 

The Epidemiology of Food Allergy
Katrina J. Allen and Jennifer J. Koplin

KEY CONCEPTS
Food allergy is on the increase in developed countries,
although good-quality prevalence data are lacking.
 Factors contributing to the epidemic appear to be related
to the modern lifestyle but as yet are poorly understood.
 The population prevalence of the four most common
IgE-mediated food allergies in infancy and childhood by
challenge-proven outcomes are approximately: cows’
milk (2–3%), egg (1–2%), peanut (1–2%) and tree nuts
(<1%), although there is marked heterogeneity in the
quality of studies to date.
 The incidence of food allergy-related anaphylaxis, the
most severe consequence of food allergy, is rising
particularly in the under 4-year age group.


Introduction
Childhood food allergy is an evolving public health
problem that appears to have risen rapidly in industrialized countries.1 Despite an increasing number
of studies mounted to investigate the rise of both
allergic disease in general and food allergy in particular, the cause of the epidemic of food allergy
remains elusive.
It is estimated that about a quarter of the population will have an adverse reaction to food (of which
food allergy is just one type) during their lifetime,2
most of which will occur during infancy and early
childhood. An estimated 10–15% of children report
symptoms of food allergy, although the prevalence
of IgE-mediated food allergies (i.e. symptoms of
© 2012, Elsevier Inc

There is little information about the population
prevalence of challenge-proven non-IgE-mediated food
allergies.
 Future epidemiological studies should address previous
study design deficiencies. For prevalence estimates,
population-representational sampling frames should
be employed. Appropriate adjustment for potential
confounding factors such as family and personal
history of allergy, and as genetic markers become
available, genetic predisposition, will be critical to
understanding risk factors for the development of
food allergy.


food allergy in the context of a positive skin prick
test) is reported to be lower, at approximately 6–8%
in children under 3 years and 3–4 % of the adult
population.3 By contrast, not much is known about
the prevalence of non-IgE-mediated food allergies,
although both eosinophilic esophagitis and celiac
disease have been documented to be increasing.4,5
There has been a significant increase in public
awareness of food allergies, with broad media
attention, owing to the concerning increase in the
prevalence of both food allergy and its most serious
manifestation, anaphylaxis. However, some medical
practitioners remain skeptical about the role of
food allergies in a number of clinical syndromes,
such as atopic dermatitis, colic and gastroesophageal reflux in infancy, despite an increasing body of

Food Allergy

evidence that food allergy can contribute to these
conditions.6

How do we define and measure
food allergy?
As outlined in Chapter 4, food allergy is defined as
an abnormal immunologic response to food proteins resulting in an adverse clinical reaction, and
can be broadly divided in to two types: those that
are mediated by food-specific immunoglobulin
class E (IgE) antibodies and those that are not. Of
the two, much more is known about IgE-mediated
than non-IgE-mediated food allergy. More than
90% of IgE-mediated food allergies in children are
caused by just eight food items: cows’ milk, soy,
hen’s egg, peanuts, tree nuts, wheat, fish and shellfish. Most children with cows’ milk and egg allergy
develop tolerance by late childhood, but allergies
to peanut, sesame seeds and tree nuts are more
persistent, with less than 20% developing tolerance.7 As a result, cows’ milk and egg allergies are
uncommon in adults and allergies to peanuts, tree
nuts, fish and shellfish predominate.

There have been many studies in the past few
decades suggesting that food allergy is over-reported
by individuals.8 There are many reasons for this.
Symptoms of food intolerance may be mistaken for
food-allergic symptoms, or poorly defined symptom
complexes such as recurrent abdominal pain,
chronic fatigue or attention deficit hyperactivity
disorder may be attributed to allergic reactions to
food even where there is no evidence to support
such contentions. Furthermore, although there are
well-described diagnostic criteria for IgE-mediated
food allergies (i.e. evidence of an acute allergic reaction, either through history or food challenge, in
the context of positive IgE antibodies to the food
in question), non-IgE-mediated food allergies can
be difficult to accurately diagnose and depend
for the most part on elimination–rechallenge
sequences performed in the home environment. As
such, any study on the prevalence of food allergy
needs to be contextualized by the outcome used
to define the condition. Table 3.1 outlines the
strengths and limitations of various study methodologies employed to measure prevalence.
Ideally, studies of the prevalence of IgE-mediated
food allergy use double-blind placebo-controlled

Table 3.1  Strengths and weaknesses of various study design and outcome methodology for the assessment of food
allergy prevalence

Outcome

Strengths

Limitations

DBPCFC

‘gold standard’ for diagnosis

Expensive, time-consuming, risk of anaphylaxis in allergic
individuals, usually has fairly low compliance rate

Open food
challenges

Less time-consuming, likely to
have improved compliance rates
compared with DBPCFC

Difficult to confirm whether delayed or subjective
symptoms are due to food ingestion without the use of a
placebo arm

Likely to be accurate for detecting
immediate objective symptoms of
allergy

Risk of anaphylaxis in allergic individuals

Self or parent-report
alone

Inexpensive, no risk of adverse
reaction in the allergic individual,
expect high compliance rates

Known over-reporting of allergy by individuals

Food-specific IgE
antibodies (SPT or
blood test)

Blood test poses no risk of allergic
reaction even in highly allergic
individuals

Using low threshold to define sensitivity – will
overestimate proportion with true allergy

SPT relatively non-invasive

Using high threshold to define sensitivity – will miss some
allergic individuals with lower levels

Improved accuracy compared
with report of symptoms or
food-specific IgE antibodies alone

Possible to have detectable levels of IgE antibodies in the
absence of previous overt exposure to a food – unclear
whether these individuals would react on ingestion

Self- or parent-report
+ food-specific IgE
antibodies

34

Individuals can be allergic to a food even in the absence
of previous overt exposure to that food – no information
on food allergy for these individuals

The Epidemiology of Food Allergy

food challenges (DBPCFC) – the gold standard for
the diagnosis of IgE-mediated food allergy. Because
this procedure is expensive, time-consuming, poses
a small risk of food challenge induced-anaphylaxis
to the individual and generally has low compliance
rates among study participants, a number of alternative methods have been used in epidemiological
studies. These include open food challenges without
the use of a placebo arm, and self- or parentreporting of acute (and usually objective) allergic
symptoms, sometimes combined with measurement of levels of IgE specific to food allergens.
Open food challenges pose the same level of risk as
DBPCFC but are less time-consuming and therefore
might achieve better compliance, but are best
limited to studies of younger study participants
(e.g. less than 2 years of age) as patient-reported
subjective symptoms are not likely to compromise
the challenge outcome. Both self-reported and
parent-reported food allergies are likely to overestimate true food allergy.
Although a number of publications have described
in detail the methodology of food challenge protocols, it is rather surprising that without exception
none have clearly delineated beforehand which
particular symptoms constitute a positive versus a
negative challenge. Although most protocols state
that a positive challenge is demonstrated by evidence of an immediate reaction consistent with
IgE-mediated food allergy such as urticaria, angio­
edema or anaphylaxis, none recommend how to
interpret more subjective symptoms such as abdominal pain or nausea, or the more ubiquitous and
less clearly defined sign of an eczema flare. Nor
are there published guidelines regarding the interpretation of a small number of transient urticarias
during a challenge. As such, challenge-proven
outcomes, albeit the gold standard, may also be
limited by interpretative differences between
studies.

CLINICAL CASE
An 11-year-old girl was first diagnosed with peanut allergy
at the age of 2 years following an acute allergic reaction to
a bite of a peanut butter sandwich. Within minutes of
ingestion she developed facial angioedema and
generalized urticaria, which resolved spontaneously over
the next several hours. She was referred to an allergist for
assessment, where a history was obtained and
confirmation of an IgE-mediated peanut allergy was made
in the context of a large positive skin prick test wheal
15 mm in size (and a negative saline control). The child
had concurrent asthma and was prescribed an adrenaline

3

(epinephrine) autoinjector, with advice about allergen
avoidance and a demonstration about how and when to
use adrenaline. She was monitored every 1–2 years with
serial skin prick tests. At ages 3, 5 and 7 years her SPT
remained elevated above 8 mm. However, at age 9 her
SPT was 6 mm and at 11 it had fallen to 4 mm. She had
not had any accidental ingestion reactions to peanut since
her initial diagnosis. At the age of 11, when her SPT was
4 mm, an oral food challenge was recommended which
was DBPCFC. The girl developed nausea and mouth
tingling with the second dose of the placebo arm, but
then went on to successfully tolerate the allergen arm and
is now tolerant to peanuts.

A further limitation of even the small number
of studies that have conducted formal graded
food challenges is that they have not addressed
the question of whether study participants are
representative of the population from which they
were sampled. The generalizability of their results
may therefore be poor. Although many cohort
studies are plagued by low participation, one
problem which is particular to studies of allergy is
the tendency for families at high risk of disease to
be over-represented among participants. The extent
to which this type of selection bias may affect
results is rarely formally assessed, although recent
cohort studies of food allergy have begun to address
this using short questionnaires to assess the pre­
valence of risk factors for allergy among those
who do not wish to undergo testing for food
allergy.9
Owing to the difficulties associated with performing large-scale studies of challenge-proven food
allergy, many population-based prevalence studies
have relied on the indirect marker of food-specific
IgE-antibodies. Methods used to detect the presence
of IgE specific to food allergens include skin prick
testing (SPT) or in vitro measurement of food
allergen-specific IgE using the CAP-fluoroenzyme
immunoassay (CAP-FEIA) or radioallergosorbent
test (RAST). For these three methods, individuals
are declared to have tested positive if the size of the
wheal (SPT) or measured IgE level (CAP-FEIA or
RAST) exceeds a prespecified threshold. Such individuals are said to be ‘sensitized’ to the food being
studied, but confirmation of food allergy at least
requires symptomatic ingestion of the food.
However, at least 50% of individuals with a positive
SPT have confirmed food allergy by formal food
challenge, and if higher cut-off wheal sizes are used
it is possible to increase the proportion of those
above the threshold wheal size with food allergy
to >95%.10 Similar positive predictive values for
35

Food Allergy

serological food-specific IgE antibodies have also
been published.11
Even the most severe consequence of food allergy,
anaphylaxis, is limited by varying opinions on what
constitutes anaphylaxis. Although variations in
definition may not significantly affect clinical care,
problems arise when attempting to determine the
population prevalence of this condition. Several
classification systems have been used; however, a
recent consensus document has defined anaphylaxis as a ‘serious allergic reaction that is rapid in
onset and may cause death’, and proposed diagnostic criteria for use in clinical care.12 According to
these criteria, a diagnosis of anaphylaxis can be
made if there is involvement of the respiratory or
cardiovascular systems during an allergic reaction;
or if a less severe reaction occurs in the setting of
previously diagnosed allergy and likely exposure to
the relevant allergen.

What is the current prevalence of
food allergy?
Because of the difficulties in measuring food allergy,
discussed above, the true prevalence has been difficult to establish. Existing studies of the incidence,
prevalence and natural history of food allergy are
difficult to compare owing to inconsistencies and
deficiencies in study design and variations in the
definition of food allergy. Although over 170 foods
have been reported to cause IgE-mediated reactions,
most prevalence studies have focused only on
the eight most common food allergens, as these
account for more than 90% of presentations to
allergists.
Rona et al.8 assessed data from 51 publications
and provided separate analyses for the prevalence
of food allergy for five common foods (cows’ milk,
hen’s egg, peanut, fish and shellfish), stratified by
whether the studies were in adults or children. The
investigators report a pooled overall prevalence of
self-reported food allergy (Fig. 3.1a) for adults and
children of 13% and 12%, respectively, to any of
these five foods. However, pooled results are far
lower (about 3%) when food allergy is defined as
either sensitization alone, sensitization with symptoms (Fig. 3.1b), or positive double-blind, placebocontrolled food challenge (Fig. 3.1c). This difference
between reported food allergy and food allergy
assessed by objective measures confirms that such

36

allergies are over-reported by patients, and that
objective measurements are necessary to establish a
true food allergy diagnosis.

CLINICAL CASE
A 2-year-old boy presented with intermittent constipation
that commenced at around 12 months of age when he
was converted from cows’ milk formula to fresh cows’ milk.
He had been exclusively breastfed until 6 months of age,
at which point he was started on solids and weaned on to
cows’ milk formula. He had not had colic, reflux,
constipation or other gastrointestinal symptoms in the first
12 months of life. Further questioning elicited that he had
developed an acute episode of fever and vomiting around
12 months of age, and the constipation had developed
within days of that episode. The patient’s mother had
recently started the child on soy milk, with little change in
bowel habit. Upon presentation to the allergist a history
was elicited that suggested that the constipation was
highly unlikely to be related to cows’ milk allergy. A skin
prick test to cows’ milk was negative, and 1 month of stool
softeners was prescribed plus a cows’ milk-free diet. The
parents were then advised to cease the stool softener and
reintroduce cows’ milk into the diet, and to return for
review if the constipation recurred. The parents
telephoned to inform the allergist that the child’s
constipation had resolved and not recurred when milk was
reintroduced.

Two recent cohort studies from the UK and
Denmark reported that the foods most often
responsible for symptoms of food allergy in infants
and young children were egg, cows’ milk and
peanuts. In the Danish study, the prevalence of egg
and milk allergy both reached a peak at around 18
months of age, at 2.4% and 1.0% for egg and milk,
respectively, with around 20% becoming tolerant
to egg by 3 years and 100% becoming tolerant to
milk by 6 years of age.13 In a recent Australian study,
the prevalence of challenge-proven peanut allergy
at 1 year of age was 3%, sesame allergy 0.8% and
raw egg allergy 8.9%.14
Both prevalence figures and the spectrum of food
allergens appear to vary considerably between
geographical regions, and are thought to reflect
variations in diet between different cultures. Alternatively, some of the differences in food allergy
prevalence between regions may be explained by
either genetic variation across populations or variations in exposure to environmental factors, such
as sunlight (i.e. related to vitamin D levels) or
factors related to the hygiene hypothesis (as discussed below).

The Epidemiology of Food Allergy

Dalal (2002)
Tariq (2000)
Rance (2005)
Garcia Ara (2003)
Kristjansson (Ice)(1999)
Eggesbo (1999)
Host (1990)
Bivalkevich (1990)
Frongia (2005)
Kristjansson (Swe) (1999)
Schrander (1993)
Penard-Morand (2005)
Roehr (2004)
Brugman (1998)
Isolauri (2004)
Rance (2005)
Bockel-Geelkerken (1992)
Perreira (2005)
Gislason (2000)
Emmett (1999)
Isolauri (2004)
Young (1994)
Woods (2001)
Falcao (2004)
Jansen (1994)
Altman (1996)
Woods (2002)
Marklund (2004)

Milk
0–4 years
P<0.001

Peanut
0–4 years
P<0.001

5–16 years
P<0.001

Adults
P<0.001

Total P<0.001

Combined
0

5–16 years
P<0.001

Adults
P<0.001

Total P<0.001

Combined
0
Dalal (2002)
Sicherer (2004)
Eggesbo (1999)
Kristjansson (Swe)(1999)
Kristjansson (Ice)(1999)
Perreira (2005)
Sicherer (2004)
Roehr (2004)
Bockel-Geelkerken (1992)
Brugman (1998)
Penard-Morand (2005)
Rance (2005)
Sicherer (2004)
Woods (2001)
Falcao (2004)
Altman (1996)
Emmett (1999)
Schafer (2001)
Marklund (2004)
Osterballe (2005)
Gislason (2000)

Kristjansson (Swe)(1999)
Rance (2005)
Sicherer (2003)
Dalal (2002)
Kristjansson (Ice)(1999)
Grundy (2002)
Rance (2005)
Sicherer (1999)
Penard-Morand(2005)
Emmett (1999)
Sicherer (2003)
Bockel-Geelkerken (1992)
Perreira (2005)
Kagan (2003)
Schafer (2001)
Kanny (2001)
Woods (2002)
Sicherer (1999)
Sicherer (2003)
Marklund (2004)
Altman (1996)
Emmett (1999)

2

4
Percentage

6

8

Fish

Combined
0

2

Percentage

4

Dalal (2002)
Kristjansson (Ice)(1999)
Bivalkevich (1990)
Kristjansson (Swe) (1999)
Rance (2005)
Tariq (2000)
Eggesbo (1999)
Frongia (2005)
Penard-Morand (2005)
Perreira (2005)
Rance (2005)
Bockel-Geelkerken (1992)
Roehr (2004)
Altman (1996)
Falcao (2004)
Woods (2002)
Emmett (1999)
Marklund (2004)
Schafer (2001)
Gislason (2000)
Young (1994)

0–4 years
P<0.001

Combined

5–16 years
P<0.001

Adults
P<0.001

Kristjansson (Swe)(1999)
Kristjansson (Ice)(1999)
Sicherer (2004)
Perreira (2005)
Rance (2005)
Sicherer (2004)
Bockel-Geelkerken (1992)
Woods (2002)
Sicherer (2004)
Kanny (2001)
Marklund (2004)
Gislason (2000)
Altman (1996)
Lunet (2005)
Falcao (2004)
Woods (2001)

Total P<0.001

Combined

3

2

4
Percentage

Egg

6

8
0–4 years
P<0.001

5–16 years
P<0.001

Adults
P<0.001

Total P<0.001
0

5
Percentage

Shellfish

0–4 years
P<0.001
5–16 years
P<0.001
Adults
P<0.001

Total P<0.001
0

5

Percentage

10

A

Figure 3.1  Population prevalence of (A) self-reported hypersensitivity to specific foods: peanut, cows’ milk, eggs, fish and shellfish,
stratified by age; (B) symptomatic food allergy in the context of a positive skin prick test or serological IgE to any food, fish, shellfish,
peanuts, cows’ milk and egg stratified by age and; (C) the prevalence of challenge-proven allergy to any food, fish, cows’ milk, egg. P
values indicate level of heterogeneity by age group and total. Reprinted with permission from: Rona RJ, Keil T, Summers C, et al. The
prevalence of food allergy: A meta-analysis. J Allergy Clin Immunol 2007; 120: 638–46.

37

Food Allergy

Kristjansson (Ice)(1999)

Any food
0–4 years
P=0.462

Kristjansson (Swe)(1999)
Kaczmarski (1999)

Kristjansson (Ice)(1999)

Peanut
0–4 years
P=0.116

Kristjansson (Swe)(1999)
Dalal (2002)

Roehr (2004)

5–16 years P=N/A
Adults
P=0.001

Zuberbier (2004)

Tariq (1996)
5–16 years
P=0.125

Perreira (2005)
Roehr (2004)

Bjornsson (1996)
Woods (2002)

Kagan (2003)
Adults
P=N/A
Total P<0.001

Zuberbier (2004)
Total P<0.001

Combined
0

2

4
Percentage

6

0

Egg
Dalal (2002)

0–4 years
P<0.001

Arshad (2001)

Combined

8
Kristjansson (Ice)(1999)

2
Percentage

4

Milk
0–4 years
P<0.001

Kristjansson (Swe)(1999)
Garcia Ara (2003)

Kristjansson (Ice)(1999)

Dalal (2002)

Kristjansson (Swe)(1999)
Roehr (2004)

5–16 years P=N/A
Adults
P=N/A

Zuberbier (2004)

Total P<0.001

Combined
0

1

2
Percentage

3

Host (1990)
5–16 years
P=N/A
Adults
P=1.00

Roehr (2004)
Woods (2002)
Zuberbier (2004)

Total P<0.001

Combined
-1

0

1
Percentage

2

3

Shellfish

Fish

5–16 years
P=N/A

Dalal (2002)

0–4 years
P=N/A

Roehr (2004)

Roehr (2004)

5–16 years P=N/A

Zuberbier (2004)

Zuberbier (2004)

Adults
P=N/A

Woods (2002)

Adults
P=0.013

Combined

Total P<0.001

Combined

Total P<0.001

-0.5

0

Percentage

0.5

1

0

0.5
1
Percentage

1.5

B

Figure 3.1  Continued

Estimates of the prevalence
of anaphylaxis
Food allergy is the leading cause of anaphylaxis
treated in hospital emergency departments in
Western Europe and the United States. The epidemiology of anaphylaxis has recently been reviewed.15
In the United States, food allergy alone appears to
account for approximately 30 000 anaphylactic
reactions, 2000 hospitalizations, and an estimated
200 deaths each year. The population prevalence of
anaphylaxis has been difficult to quantify owing to
38

a lack of consensus on the definition of anaphylaxis, analysis of different sample populations (e.g.
emergency department presentations, hospital
admissions, general practitioner presentations, specialist allergist presentations), and the use of varying
methodologies for data collection.
Population studies have estimated the incidence
or prevalence of anaphylaxis in Western countries
to be in the range of 8–50 per 100 000 person-years,
with a lifetime prevalence of 0.05–2.0%. Reported
population prevalence rates vary internationally,
with studies from the US reporting 49.8 per 100 000
person-years, the UK 8.4 per 100 000 person-years,

The Epidemiology of Food Allergy

Osterballe (2005)

Fish

Any food
0–4 years P=N/A
5–16 years P<0.001

Perreira (2005)
Roehr (2004)

Adults
P=0.001

Osterballe (2005)
Zuberbier (2004)
Young (1994)
Janssen (1994)

0–4 years P=0.461

Kristjansson
(Ice)(1999)
Kristjansson
(Swe)(1999)
Osterballe (2005)
Osterballe (2005)

Adults
P=N/A

Combined

Total P<0.001

Total P<0.001

Combined
0

3

5

Percentage

10

15

-1

Milk

0

Percentage

1

2

Egg
0–4 years P=0.001

Host (1990)

0–4 years P<0.202

Madrigal (1996)

Osterballe (2005)
Osterballe (2005)

Madrigal (1996)
Schrander (1992)

5–16 years
P=N/A

Roehr (2004)

Altinas (1995)
Roehr (2004)

5–16 years P=N/A

Osterballe (2005)

Adults
P=0.036

Janssen (1994)

Adults
P=N/A

Osterballe (2005)

Total P<0.044

Combined
Total P<0.001

Combined
0

1

Percentage

2

3

-1

0

1
Percentage

2

3

C

Figure 3.1  Continued

and Australia 13 per 100 000 person-years. However,
the variation in prevalence rates may reflect differences in sample populations, data collection
methods and definitions of anaphylaxis rather than
true differences in anaphylaxis rates between countries, as the UK prevalence estimate was derived
from a GP database, the US incidence rate was
determined from a population cohort in Minnesota, and the Australian minimum incidence of
anaphylaxis in the population was estimated based
on the number of anaphylaxis cases presenting to
an allergy specialist in a captured population. Disparate prevalence rates have also been found in
separate studies from the same country, with a
second US study reporting a much lower prevalence
of anaphylaxis of 10.5 per 100 000 person-years for
children and adolescents enrolled at a health maintenance organization.

Anaphylaxis admissions data from national database systems in the UK and Australia revealed
a population prevalence of 3.6 per 100 000
(2003/2004) and 8.0 per 100 000 (2004/2005),
respectively. The varying prevalence between the
two countries may be due to underlying differences
in the prevalence of food allergy in general, or more
simply to a difference in coding practices between
the two types of medical system. Using a statewide
administrative database, the rate of anaphylaxis
admissions for New Yorkers aged 0–20 years was
4.2 per 100 000. However, these admissions figures
are likely to underestimate the true population
prevalence of anaphylaxis, as not all presentations
will result in hospital admission, and misclassification of the presenting disorder in hospital settings
may occur. A review of National Electronic Injury
Surveillance System data from 34 participating
39

Food Allergy

emergency departments over a 2-month period in
2003 found that 57% of likely anaphylactic events
were not assigned an ED diagnosis of anaphylaxis.

Epidemiology of fatal anaphylaxis
Data from national mortality reporting systems in
the UK and Australia estimate the prevalence of
anaphylaxis fatalities from all causes to be 0.33
deaths per year per million population in the UK,16
with a higher rate in Australia of 0.64 deaths per
year per million population.17 Fatal episodes of
anaphylaxis in the UK were reported to be due to
food/possible food in 31% of cases, with the
remainder due to medication (44%), insect sting
(23%) and other (4%). In contrast, only 6% of
anaphylaxis deaths in the Australian study were due
to food, with the majority of deaths due to
medication/probable medication (57%) and insect
sting (18%).
For food anaphylaxis, admissions peaked in
males under 5 years of age, whereas deaths occurred
predominantly in females aged between 10 and 35
years. Risk factors for a poor outcome from an
episode of food-related anaphylaxis include age
(risk is highest in adolescents and young adults),
peanut or tree nut allergy, coexisting and poorly
controlled asthma, posture (failure to be kept in the
supine position), lack of access to self-injectable
adrenaline, and failure to administer adrenaline in
a timely manner. Although never formally investigated, hypothetical reasons for poorer outcomes in
the adolescent and young adult age group include
increased risk-taking behaviors, issues of transition
from parental locus of control, failure to adequately
educate young people about the risks of anaphylaxis at the time that they are taking increased
responsibility for their own health, and finally an
increased prevalence of both asthma and poorly
managed asthma in these age groups compared to
those under 5 years of age.

Role of race and gender in
food allergy
Although gender disparities in the prevalence of
some allergic disorders, including allergic asthma,
have been well described, the relationship between
gender and food allergy is less clear.18 The relationship between gender and allergy appears to vary by
40

age, with studies of allergic asthma showing that in
childhood males are more often affected, whereas
in adults the reverse is true. Studies of gender and
food allergy are limited, and few have used oral
food challenges as the outcome. Of the data that
are available, it appears that females are more likely
than males to report food allergy in adulthood.
Findings in childhood are less clear, with some
studies of peanut sensitization and allergy finding
a male predominance whereas others found no
gender differences.
Similarly, racial/ethnic differences in asthma
prevalence have also been well described, although
so far there have been very few studies investigating
the influence of ethnicity on the likelihood of
developing food allergy. One UK study found that
non-Caucasian infants were overrepresented in a
pediatric food allergy clinic compared to general
pediatric clinics.19 In the US, the 2007 National
Health Interview Survey found that non-Hispanic
children had higher rates of reported food allergy
than Hispanic children.20

Is the incidence of food
allergy increasing?
The prevalence of IgE-mediated food allergies
appears to be increasing in industrialized countries
following the previously documented rise in prevalence of other atopic conditions such as asthma,
eczema and allergic rhinitis. The paucity of earlier
studies on prevalence has precluded a clear evidence base for a rise in food allergy, although there
is circumstantial evidence to suggest that it has
occurred since the early 1990s.
Recent studies have tried to confirm anecdotal
evidence of an increased incidence of peanut allergy.
In a UK study, Grundy et al.21 found an increase in
reported peanut allergy from 0.5% to 1.5% in two
sequential early childhood cohorts from the same
geographic area, surveyed 6 years apart. However,
the difference did not reach statistical significance,
perhaps due to lack of numbers, or because the
number of years between measurement points may
have been insufficient to demonstrate an increase
in allergy.
Between two United States-wide phone surveys,
the prevalence of self-reported peanut and/or tree
nut allergy increased from 0.6% to 1.2% between
1997 and 2002 among children, though no change
was observed for adults.1 In a more recent Canadian

The Epidemiology of Food Allergy

study, the prevalence of peanut allergy was found to
be stable between 2000–2002 (1.63%, 95% CI
1.30–2.02%) and 2005–2007 (1.50%, 95% CI
1.16–1.92%).22,23 A systematic review by Chafen
et al.24 concluded that it is unclear whether there
has been a real rise in food allergy over the last few
decades, and estimated that the current prevalence
of food allergy in the US, Europe and Australia could
be as low as 1% or as high as 10%. Reliable surveillance of allergy prevalence within populations will
be required to measure any future increases.
Hospital records have been examined in an
attempt to assess the prevalence of more serious
allergic reactions. Poulos and colleagues25 found a
continuous increase in the rates of hospital admission for angioedema (3.0% per year), urticaria
(5.7% per year), and, importantly, anaphylaxis
(8.8% per year), over a 10-year period from 1993.
A fivefold increase in food-induced anaphylaxis
among children under 5 years was a notable finding,
and parallels the findings of population-based
prevalence studies.

What is the cause of the rise in
incidence of IgE-mediated food allergy?
The reasons for the presumed increase in food
allergy prevalence are not known, but the short
period over which the increase has occurred suggests that genetic factors alone cannot be causative,
as changes to the genome occur at an evolutionary
pace. Environmental factors must therefore be
central, although these may be mediated through
epigenetic modification (as discussed below). It
appears that these environmental factors are linked
to the ‘modern lifestyle’, as food allergy is more
common in developed than developing countries,
and migrants appear to acquire the incident risk of
allergy of their adopted country. Although environmental factors, including those associated with the
hygiene hypothesis, as well as dietary factors have
been found to be associated with the development
of eczema and atopy, it is not clear whether these
also play a role in the development of food allergy.26
As well as the factors associated with other atopic
diseases, it is likely that there are some food allergyspecific risk factors. These might include change in
methods of food preparation, increased use of antacids and proton pump inhibitors, use of medicinal
creams containing food allergens, and the later
introduction of allergenic foods into the diet of
infants.

3

The ‘hygiene’ hypothesis
Multiple environmental factors associated with the
hygiene hypothesis (i.e., the hypothesis that early
exposure to microbial antigens promotes healthy
immune development and reduces the risk of
developing allergies) have been linked to allergic
outcomes such as asthma or allergic sensitization.
These include cesarean section delivery, companion
animal ownership, exposure to other children
(either siblings or through childcare attendance),
and exposure to farm animals or domestic pets
(Fig. 3.2).

The impact of gastrointestinal
flora composition
The composition of the gastrointestinal flora in
infancy is affected by various factors, but as the fetal
intestine is sterile the initial colonizing events in
the infant are likely to be highly important in governing the type of commensal bacteria present in
the first few days of life, and possibly longer. The
initial colonizing event is likely to be influenced by
mode of delivery, with infants delivered by cesarean
section having less contact with maternal flora,
which acts as a source of intestinal bacteria for the
newborn. It has been hypothesized that differences
in colonization might lead to an increased risk of
allergy among infants born by cesarean section. It
is possible that commensal bacteria in the gastrointestinal tract may exert an immunomodulatory
effect that leads to tolerance to both the commensal
bacteria themselves and also to ingested food allergens. A recent systematic review of the literature
identified only two studies that examined the
relationship between mode of delivery and food
allergy, and a further two used sensitization as the
outcome.27 Of the studies that examined food
allergy, one found an increase among infants born
by cesarean section only if there was a maternal
history of allergy, whereas the second found no
difference in food allergy according to mode of
delivery. Further studies using objectively confirmed
food allergy as the outcome are required to determine whether delivery by cesarean section increases
the risk of food allergy.

The ‘old friends’ hypothesis
Following the initial colonizing events at birth, the
infant immune system continues to be exposed to
stimulus not only from the commensal bacteria in
41

Food Allergy
Genetic factors/family
history of atopy
Maternal smoking
Parental age
Maternal diet during pregnancy including
consumption of allergenic foods, use of probiotics
and vitamin supplements (e.g. folate, fish oil)
(direct or epigenetic effect)

Initiation of breastfeeding

Prenatal

Fetal epigenetic modification through
maternal exposure to these factors

Perinatal

Factors associated with the ‘hygiene hypothesis’
Improved sanitation
Increased immunization rates
Increased use of antibiotics
Decreased infections (H. pylori, Hepatitis A, helminths,
gastrointestinal infections)
Exposure to farm animals, domestic pets, endotoxin
Reduced microbial load in food, water
Presence of siblings

Caesarean section delivery

Infant dietary factors
Duration of breastfeeding
Maternal diet during breastfeeding
Age at first introduction of solids
Age at first introduction of allergenic foods
Use of cows’ milk-based formulas
Use of probiotics
Use of vitamin supplements

Postnatal

Exposure to
sunlight/vitamin D

Direct infant exposure

Exposure to tobacco smoke
and other environmental
pollutants

Figure 3.2  Factors potentially associated with risk of IgE-mediated food allergy.

the gastrointestinal tract but also from external
sources. The ‘old friends’ hypothesis states that the
immune system evolved at a time of constant exposure to certain organisms in the environment,
such as helminths and environmental saprophytes
found in food and water. These organisms needed
to be tolerated, either because they were harmless
and ubiquitous (environmental saprophytes) or
because mounting an immune response would
damage the host (some helminths). It is thought
that continued exposure to these organisms might
have caused downregulation of the immune
response not only to these organisms but also to
self-antigens (autoimmunity) and food allergens
(food allergy), possibly through the induction of
regulatory T cells. Reduced exposure to these groups
of organisms in the modern environment could
therefore potentially explain the increase in allergic
diseases and autoimmunity.
Other factors associated with a ‘modern lifestyle’
include myriad changes to our level of public
health, including improved sanitation, secure water
42

supplies (with associated decreased prevalence of
Helicobacter pylori infection), widespread use of
antibiotics and increasing rates of immunization,
reduced helminthic infestation, improved food
quality (and presumably less microbial load in the
food chain) as well as generally improved nutrition
and associated obesity (Fig. 3.2). These factors
might work individually or in concert to cause a
failure in the development of oral immune tolerance in the first year of life, when IgE-mediated
food allergy is most likely to develop.
These factors have all come into play some time in
the last half of the 20th century, and yet the rise in
food allergy prevalence appears in the context of the
early part of the 21st century. There is strong evidence that environmental exposures play a key role
in activating or silencing genes by altering DNA and
histone methylation, histone acetylation and chromatin structure. These ‘epigenetic’ modifications
determine the degree of DNA compaction and accessibility for gene transcription. If the hygiene hypothesis is found to be central to the rise of both atopy

The Epidemiology of Food Allergy

in general and food allergy more specifically, this
effect might be expressed through a delayed generational effect and the impact of maternal epigenetic
modification on fetal priming of the immune
system. There are now many elegant animal models
showing how environmental changes at critical
times during development (both in utero and postnatally) can profoundly alter the phenotype of
genetically identical animals through epigenetic
modification.28 These effects are currently under
investigation in a number of centers throughout the
world.

Other changes to the
gastrointestinal milieu
The allergenicity of some food allergens is reduced
or eliminated when subject to acid pH levels equivalent to those found in the human stomach (pH
1.5–3.0). Untersmayr and colleagues29 hypothesized that the widespread use of anti-ulcer mediation in the last 20–30 years may have contributed
to an increasing prevalence of food allergy. In a
study of adult patients they found that 3 months of
anti-ulcer therapy resulted in an increase in foodspecific IgE in 25% of all treated patients, and there
was a boost of pre-existing food-specific IgE in 10%.
They concluded that the relative risk for the increase
of an IgE response to food allergens after only 3
months of treatment was 10.5. In newborns, the
intragastric pH ranges from 6.0 to 8.0. After birth
there is a burst of acid secretion, resulting in transient adult gastric pH levels (pH 1.0–3.0) for 24–48
hours. However, after these first days of life gastric
acid production remains low and adult pH levels
in the stomach are not reached again until the
average age of 2 years. It has been suggested that
the widespread and increasing use of agents such
as proton pump inhibitors in infants with ‘colic’ in
Western populations (for presumed gastroesophageal reflux) may be one of the significant contributory factors of the ‘modern lifestyle’ resulting in an
increased prevalence of allergies.
Similarly, H. pylori-associated atrophic gastritis
reduces acid secretion. The infection is usually contracted in the first years of life and tends to persist
indefinitely if untreated. At least half of the world’s
human population has H. pylori infection, but rates
of infection have fallen dramatically in developed
countries over the last 20 years for as yet unidentified reasons. Widespread use of antibiotics,
improved public hygiene measures and better water

3

quality may all play a role in its decreasing prevalence, which could coincide with the rising prevalence of food allergy.
Following on from this line of thought, the dramatic change over the last 30 years in the timing of
introduction of solids from around 3 months of age
to after 6 months (as discussed below) could potentially mediate changes in acid secretion and result
in changed allergenicity of foods at a critical window
of opportunity.

Evidence for change in the timing of
introduction of solids and the impact on
food allergy prevalence
Along with changes in food quality and a likely
decrease in the microbial content of foods, there
has also been a trend to delay the age at which
foods are introduced to infants. Whereas in the
1960s infants were typically given solid foods in the
first 3 months of life, the 1970s saw the introduction of guidelines recommending delayed introduction of solids until after 4 months of age because
of a perceived link between the early introduction
of gluten and celiac disease. By the late 1990s,
expert bodies began to recommend delaying solids
until after 6 months of age, with a further delay in
the introduction of allergenic foods such as egg and
nuts until at least 2 years of age recommended for
infants with a family history of allergy. This did not,
however, appear to have the desired effect of reducing the prevalence of food allergy, and in 2008, lack
of evidence of a protective effect led to the removal
of advice to delay the introduction of any foods
beyond 4–6 months of age.
Recently, it has been suggested that delayed introduction of allergenic foods may actually prevent the
normal development of tolerance, which occurs
when foods are introduced during a ‘window of
opportunity’ in early infancy.28 This is consistent
with the observation that Israeli infants are introduced to peanut at a young age, yet Israeli schoolchildren experience a low prevalence of peanut
allergy, whereas the opposite is observed in the
UK.30 Of the studies to date investigating the relationship between timing of introduction of allergenic foods and food allergy, only one has controlled
for potential confounding factors such as personal
and family history of allergy.31,32 This study found
that infants introduced to cooked egg at 4–6 months
of age were less likely to have egg allergy at 1 year
of age compared to those introduced to egg later.
43

Food Allergy

Randomized controlled trials of the early introduction of allergenic foods are currently under way to
clarify the degree to which such an effect may be
found in association with the development of food
allergies.

Breastfeeding and food allergy
The relationship between breastfeeding and food
allergy is currently not clear. Since randomized controlled trials allocating infants to breastfeeding or
not breastfeeding are not ethically feasible, evidence is limited to observational studies which
have so far shown conflicting results. Like studies
of the timing of introduction of foods, observational studies of breastfeeding and food allergy are
limited by the possibility of confounding by a
family history of allergy or early signs of atopic
disease in the infant. Studies of breastfeeding and
food allergy are also complicated by the fact that
infants can be exclusively breastfed (without the
use of supplementary formulas or other foods) or
breastfed with supplementary formulas, in which
case the amount of breastfeeding compared with
formula may vary between individuals. It has also
been hypothesized that breastfeeding at the time
when foods are introduced into the infant diet,
rather than the duration of breastfeeding alone,
may be protective against the development of
allergy,28 although this has yet to be confirmed.

The role of genetics in predisposition to
food allergy
There is increasing evidence for a strong genetic
component to allergies, and particularly food
allergy. Twin studies have shown that the con­
cordance rate for peanut allergy was much higher
among monozygotic (64.3%) than dizygotic (6.8%,
p < 0.0001) twin pairs.33 A recent study of familial
aggregation observed the heritability of common
food allergies (sesame, peanut, wheat, milk, egg
white, soy, walnut, shrimp, cod fish) to be
15–30%.34
Food allergy occurs more frequently in infants
with eczema. Recently, eczema has been found to
be closely associated with defects in skin barrier
permeability and loss of function mutations in the
filaggrin (FLG) gene. A number of recent studies
have linked null mutations (R501X and 2282del4)
in FLG with an increased susceptibility to eczema.35
Individuals with two null alleles in FLG have been
44

shown to be 4–7 times more likely to have eczema
than those without.36 FLG appears to play an essential role in epithelial integrity: a severe breakdown
in the function of the protein produced can result
in the skin disorder ichthyosis vulgaris. However, it
is not known whether defects of FLG and/or other
epithelial barrier functions may act independently
to increase the risk of food allergy, and no studies
to date have investigated the relationship between
food allergy and the FLG null mutations. As the
most strongly associated genetic factor currently
linked to eczema, it will be important to refute or
establish a genetic association of FLG variants with
food allergy.
Despite many attempts to investigate risk factors
for food allergy, few have yet been identified. This
may be because population-based studies have not
been able to take into account the fact that food
allergy is at least partly genetically determined, as
the specific genes that confer susceptibility to food
allergy remain unknown. Environmental factors
that increase the risk of food allergy may act differently depending on genetic risk, an issue which
cannot be completely addressed until genetic risk
factors for food allergy are identified.

Food allergy and the ‘atopic march’
Atopic diseases such as asthma, allergic rhinoconjunctivitis, eczema and food allergy are closely
related. Their manifestations often present in a
characteristic sequence that has been named the
atopic march. The first signs of atopic diseases are
usually food allergies and eczema, which have their
greatest incidence during the first 3 years of life. In
contrast, IgE-mediated responses to environmental
allergens, allergic rhinoconjunctivitis and asthma
symptoms mostly develop later in life. Infants who
develop early symptoms of allergy, such as sensitization to cows’ milk or egg, are also more likely to
go on to develop sensitization to environmental
allergens and asthma.
Despite the delayed onset between allergen exposure and exacerbation, eczema is often associated
with IgE-mediated food allergy, and SPT or foodspecific serum IgE testing is helpful in predicting a
response to the elimination of cows’ milk protein
and other food allergens. Infants with early-onset
eczema (within the first 6 months) of at least moderate severity have a high incidence of food allergies, in particular to egg and cows’ milk.

The Epidemiology of Food Allergy

Non-IgE-mediated food allergies
The most common food associated with non IgEmediated food allergy syndromes is cows’ milk.
This may be a function of the fact that infants are
most likely to present with non-IgE-mediated syndromes at a time when gastrointestinal mucosal
integrity is developing, and cows’ milk protein is
the most common dietary antigen during the first
year of life. It is estimated that cows’ milk proteininduced allergy occurs in up to 2% of children
under the age of 2 years.6 Most infants with nonIgE-mediated cows’ milk protein allergy develop
tolerance by the third year of life. Table 3.2 outlines
the defining features that distinguish IgE-mediated
from non-IgE-mediated food allergies and their
associated syndromes.
Enteropathy resulting from cows’ milk is one
of the better-understood non-IgE-mediated food

Table 3.2  Defining features that distinguish IgEmediated from non-IgE mediated food allergies and
their associated syndromes. Modified from Allen KJ, Hill DJ,
Heine RG. Food allergy in childhood. Med J Aust. 2006 Oct
2;185(7):394–400.

Class

IgE
mediated

Non-IgE
mediated

Time to onset
of reaction

Immediate
<1 hour

Delayed
>24 hours

Volume
required for
reaction

Small (e.g.
<10 ml)

Large (e.g.
>100 ml)

Symptoms/
syndromes

Urticaria,
angioedema,
vomiting,
anaphylaxis,
oral allergy
syndrome,
eczema

Diarrhoea, eczema,
failure to thrive,
gastrooesophageal reflux
food proteininduced
enteropathy,
enterocolitis and
proctocolitis,
multiple food
allergy

Above signs or
symptoms by
history or oral
food challenge
AND positive
IgE antibodies
(skin prick test
or cap-FEIA)

Home based
elimination and
rechallenge
sequence (no risk
of anaphylaxis)

Diagnostic
procedures

3

allergies. One prospective cohort study of newborns in Denmark found that the incidence of
cows’ milk protein (CMP) enteropathy was 2.2%
over the first year of life, with a high rate of resolution (97%) by 15 years of age.37 Reports suggest a
rapid rise in the prevalence of eosinophilic esophagitis,38 a condition that was first linked to food
allergy in 1995. Celiac disease is also reported to be
increasing in prevalence, although there are some
suggestions that improved serological screening
studies have increased the case finding for this
disease, which has a reported prevalence of 0.5–
1.0% of the community39. Although symptoms of
CMP-induced enteropathy in infancy may be
similar to those of celiac disease, the onset often
coincides with the dietary introduction of CMP,
prior to wheat exposure.
Food allergies appear to play a role in over 90%
of children with eosinophilic esophagitis (EE) and
up to 40% of infants with symptoms of gastroesophageal reflux disease (GORD) are thought
to have cows’ milk allergy.40 However, there are
no clear distinguishing features to identify dietresponsive infants with reflux disease and there is a
significant clinical overlap between EE and GORD.
Poor response to the use of proton pump inhibitors
and more than 15 eosinophils per high-powered
field on histology of esophageal biopsies are used
to distinguish GORD from EE. Most infants with
food-induced GORD or EE usually present within
a few weeks of first exposure to the implicated food,
with cows’ milk most frequently implicated in
GORD and cows’ milk, soy, wheat, other grains,
meat and poultry frequently implicated in EE. The
diagnosis of food-induced GORD or EE is made by
strict food elimination for a minimum of 2–4
weeks, and subsequent re-challenge.

CLINICAL CASE
A 14-month-old girl was referred for opinion and
management of irritability from birth, and vomiting and
loose stools with failure to thrive from around 6 months of
age. A trial of ranitidine at 2 months of age for possible
gastroesophageal reflux disease was unhelpful. She was
exclusively breastfed until 6 months of age, and there was
no improvement with a partial maternal exclusion of dairy
products. Solids were introduced at that time and breast
milk was continued until 10 months of age. Soy milk and
goats’ milk were also tried, with no clear improvement.
At 8 months of age she was therefore prescribed an
extensively hydrolyzed formula, with improvement in her
stool quality but not the vomiting. Family history included
maternal celiac disease and atopy, and a sister with
45

Food Allergy
eczema. A gastroscopy was undertaken to rule out celiac
disease and surprisingly revealed changes consistent with
eosinophilic esophagitis. Eosinophils were detected in the
following biopsies; 42/high-power field (HPF) upper, 38/
HPF mid and 28/HPF in the lower esophagus. There was
basal cell proliferation occupying more than 50% of the
epithelial thickness, and her stomach and duodenum were
normal macroscopically and microscopically. Celiac
serology was also negative (IgA 0.77). She subsequently
underwent skin prick tests (SPT) which were all negative
(cows’ milk 0 mm, egg 0 mm, soy 0 mm, wheat 0 mm), but
atopy patch testing (APT) was positive for cows’ milk
protein and soy and negative for egg and wheat. A diet
eliminating cows’ milk and soy and an amino-acid based
formula was started, with subsequent improvement of all
symptoms. A follow-up gastroscopy around 12 months
later showed a normal esophagus with only 1–2
eosinophils per high-power field detected.

Food protein-induced proctocolitis (an allergic
inflammatory process involving the distal colon)
usually presents in the first 3 months of life with
low-grade rectal bleeding in an otherwise thriving
infant, and is the commonest cause of rectal bleeding in infancy after constipation with fissure. Cows’
milk protein allergy (CMPA) is the most common
cause of proctocolitis, although other food proteins
(e.g. soy, rice, wheat) have been implicated.41 It can
occur in breastfed infants, as the antigenic protein
β-lactoglobulin has been identified in breast milk.

CLINICAL CASE
A 6-week-old infant who was otherwise thriving presented
with low-grade rectal bleeding with no evidence of
constipation or a fissure. The infant was fully breastfed and
the mother was on an unrestricted diet. The allergist
recommended maternal cows’ milk avoidance, with some
resolution of the bleeding. Additional soy exclusion (with
support from an allergy dietitian) resulted in complete
remission of the bloody stools. The mother chose to
breastfeed until the infant was 12 months of age and
delayed the introduction of cows’ milk and soy (including
solids) until that time. At the 12-month review skin prick
testing to cows’ milk was negative, and the parents were
educated regarding a home-based introduction plan
commencing the infant on a daily dose of 5 ml of cows’
milk and doubling the dose on a daily basis until a full
serving of 200 ml was tolerated, at which time the infant’s
diet was liberated to all forms of dairy as he remained
asymptomatic.

Cows’ milk protein allergy in infancy may present
with constipation.42 However, in the absence of
clear diagnostic markers there are significant difficulties in making an unequivocal diagnosis of
CMP-induced constipation, since there is a wide
range of normal stool frequency in infants,43 and
46

minor constipation at the time of weaning from
breast milk to CMF is relatively common and
usually due to non-allergic mechanisms such as the
coincidental introduction of solids. Clinical features suggestive of CMP-induced constipation
include onset in close relationship to the first
dietary introduction of CMP. There is no diagnostic
test for CMP-induced constipation, other than
CMP elimination for 2–4 weeks followed by rechallenge. Infants with severe constipation require
specialist referral to exclude anorectal malformations or Hirschsprung’s disease. Increased eosinophils on rectal biopsy support the diagnosis of
CMP-induced constipation44 and management
involves strict dietary CMP elimination.
Colic is a multifactorial condition that typically
occurs in infants between 3 and 6 weeks, with
remission occurring by 4 months of age.45 The
causal relationship between colic and CMPA is controversial, although several trials have demonstrated
a significant clinical improvement in response to
CMP elimination.46,47 Persistence of irritability
beyond 4 months may suggest an organic etiology,
including CMPA. Most infants with colic have no
associated atopic disorders, and IgE-based tests for
food allergy are not helpful. In infants with dietresponsive colic, colic behavior is mostly reduced
within 1 week of dietary modification.

References
1. Sicherer SH, Munoz-Furlong A, Sampson HA.
Prevalence of peanut and tree nut allergy in the United
States determined by means of a random digit dial
telephone survey: a 5-year follow-up study. J Allergy
Clin Immunol 2003;112:1203–7.
2. Schafer T, Bohler E, Ruhdorfer S, et al. Epidemiology of
food allergy/food intolerance in adults: associations
with other manifestations of atopy. Allergy 2001;56:
1172–9.
3. Sampson HA. Food allergy – accurately identifying
clinical reactivity. Allergy 2005;60(Suppl. 79):
19–24.
4. Prasad GA, Alexander JA, Schleck CD, et al.
Epidemiology of eosinophilic esophagitis over three
decades in Olmsted County, Minnesota. Clin
Gastroenterol Hepatol 2009;7:1055–61.
5. Cook B, Oxner R, Chapman B, et al. A thirty-year
(1970–1999) study of coeliac disease in the Canterbury
region of New Zealand. The New Zealand Medical
Journal 2004;117:U772.
6. Allen KJ, Davidson GP, Day AS, et al. Management of
cows’ milk protein allergy in infants and young
children: an expert panel perspective. J Paediatr Child
Health 2009;45:481–6.

The Epidemiology of Food Allergy
7. Ho MH, Wong WH, Heine RG, et al. Early clinical
predictors of remission of peanut allergy in children.
J Allergy Clin Immunol 2008;121:731–6.
8. Rona RJ, Keil T, Summers C, et al. The prevalence of
food allergy: A meta-analysis. J Allergy Clin Immunol
2007;120:638–46.
9. Osborne NJ, Koplin JJ, Martin PE, et al. The
HealthNuts population-based study of paediatric food
allergy: validity, safety and acceptability. Clin Exp
Allergy 2010;40:1516–22.
10. Sporik R, Hill DJ, Hosking CS. Specificity of allergen
skin testing in predicting positive open food challenges
to milk, egg and peanut in children. Clin Exp Allergy
2000;30:1540–6.
11. Celik-Bilgili S, Mehl A, Verstege A, et al. The predictive
value of specific immunoglobulin E levels in serum for
the outcome of oral food challenges. Clin Exp Allergy
2005;35:268–73.
12. Sampson HA, Munoz-Furlong A, Campbell RL, et al.
Second symposium on the definition and management
of anaphylaxis: summary report – Second National
Institute of Allergy and Infectious Disease/Food Allergy
and Anaphylaxis Network symposium. J Allergy Clin
Immunol 2006;117:391–7.
13. Eller E, Kjaer HF, Host A, et al. Food allergy and food
sensitization in early childhood: results from the DARC
cohort. Allergy 2009;64:1023–9.
14. Osborne N, Koplin J, Martin P, et al. Prevalence of
challenge-proven IgE-mediated food allergy using
population-based sampling and predetermined
challenge criteria in infants. J Allergy Clin Immunol
2011;127:668–76.
15. Tang ML, Osborne N, Allen K. Epidemiology of
anaphylaxis. Curr Opin Allergy Clin Immunol
2009;9:351–6.
16. Pumphrey R. Anaphylaxis: can we tell who is at risk of
a fatal reaction? Curr Opin Allergy Clin Immunol
2004;4:285–90.
17. Liew WK, Williamson E, Tang ML. Anaphylaxis
fatalities and admissions in Australia. J Allergy Clin
Immunol 2009;123:434–42.
18. Chen W, Mempel M, Schober W, et al. Gender
difference, sex hormones, and immediate type
hypersensitivity reactions. Allergy 2008;63:1418–27.
19. Dias RP, Summerfield A, Khakoo GA. Food
hypersensitivity among Caucasian and non-Caucasian
children. Pediatr Allergy Immunol 2008;19:86–9.
20. Branum AM, Lukacs SL. Food allergy among U.S.
children: trends in prevalence and hospitalizations.
NCHS data brief 2008;1–8.
21. Grundy J, Matthews S, Bateman B, et al. Rising
prevalence of allergy to peanut in children: Data from
2 sequential cohorts. J Allergy Clin Immunol
2002;110:784–9.
22. Ben-Shoshan M, Kagan RS, Alizadehfar R, et al. Is the
prevalence of peanut allergy increasing? A 5-year
follow-up study in children in Montreal. J Allergy Clin
Immunol 2009;123:783–8.
23. Sicherer SH, Muñoz-Furlong A, Godbold JH, et al. US
prevalence of self-reported peanut, tree nut, and

3

sesame allergy: 11-year follow-up. J Allergy Clin
Immunol 2010 Jun;125(6):1322–6. Epub 2010 May 11.
24. Chafen JJ, Newberry SJ, Riedl MA, et al. Diagnosing
and managing common food allergies: a systematic
review. JAMA 2010 May 12;303(18):1848–56.
25. Poulos LM, Waters AM, Correll PK, et al. Trends in
hospitalizations for anaphylaxis, angioedema, and
urticaria in Australia, 1993–1994 to 2004–2005. J
Allergy Clin Immunol 2007;120:878–84.
26. Allen KJ, Martin PE. Clinical Aspects of Pediatric Food
Allergy and Failed Oral Immune Tolerance. J Clin
Gastroenterol 2010;44:391–401.
27. Koplin J, Allen K, Gurrin L, et al. Is caesarean delivery
associated with sensitization to food allergens and
IgE-mediated food allergy: a systematic review. Pediatr
Allergy Immunol 2008;19:682–7.
28. Prescott SL, Smith P, Tang M, et al. The importance of
early complementary feeding in the development of
oral tolerance: concerns and controversies. Pediatr
Allergy Immunol 2008;19:375–80.
29. Untersmayr E, Jensen-Jarolim E. The role of protein
digestibility and antacids on food allergy outcomes.
J Allergy Clin Immunol 2008 Jun;121(6):1301–8.
30. Du Toit G, Katz Y, Sasieni P, et al. Early consumption
of peanuts in infancy is associated with a low
prevalence of peanut allergy. J Allergy Clin Immunol
2008;122:984–91.
31. Koplin J, Osborne N, Wake M, et al. Can early
introduction of egg prevent egg allergy in infants? A
population-based study. J Allergy Clin Immunol
2010;126:807–13.
32. Poole JA, Barriga K, Leung DY, et al. Timing of initial
exposure to cereal grains and the risk of wheat allergy.
Pediatrics 2006;117:2175–82.
33. Sicherer SH, Furlong TJ, Maes HH, et al. Genetics of
peanut allergy: A twin study. J Allergy Clin Immunol
2000;106:53–6.
34. Tsai H-J, Kumar R, Pongracicwz J, et al. Familial
aggregation of food allergy and sensitization to food
allergens: a family-based study. Clin Exp Allergy
2009;39:101–9.
35. Irvine A. Fleshing out filaggrin phenotypes. J Invest
Dermatol 2007;127:504–7.
36. Marenholz I, Nickel R, Rüschendorf F, et al. Filaggrin
loss-of-function mutations predispose to phenotypes
involved in the atopic march. J Allergy Clin Immunol
2006;118:866–71.
37. Host A, Halken S, Jacobsen HP, et al. Clinical course of
cows’ milk protein allergy/intolerance and atopic
diseases in childhood. Pediatr Allergy Immunol
2002;13(Suppl. 15):23–8.
38. Cherian S, Smith NM, Forbes DA. Rapidly increasing
prevalence of eosinophilic oesophagitis in Western
Australia. Arch Dis Child 2006;91(12):1000–4.
39. Fasano A, Berti I, Gerarduzzi T, et al. Prevalence of
celiac disease in at-risk and not-at-risk groups in the
United States: a large multicenter study. Arch Intern
Med 2003;163(3):286–92.
40. Iacono G, Carroccio A, Cavataio F, et al.
Gastroesophageal reflux and cows’ milk allergy in
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infants: a prospective study. J Allergy Clin Immunol
1996;97:822–7.
41. Lake AM. Food-induced eosinophilic proctocolitis.
J Pediatr Gastroenterol Nutr 2000;30(Suppl.):
S58–60.
42. Iacono G, Cavataio F, Montalto G, et al. Intolerance of
cows’ milk and chronic constipation in children. N
Engl J Med 1998;339:1100–4.
43. Tham EB, Nathan R, Davidson GP, et al. Bowel habits
of healthy Australian children aged 0–2 years.
J Paediatr Child Health 1996;32:504–7.
44. Iacono G, Bonventre S, Scalici C, et al. Food
intolerance and chronic constipation: manometry and

48

histology study. Eur J Gastroenterol Hepatol 2006;18:
143–50.
45. Clifford TJ, Campbell MK, Speechley KN, et al. Sequelae
of infant colic: evidence of transient infant distress and
absence of lasting effects on maternal mental health.
Arch Pediatr Adolesc Med 2002;156:1183–8.
46. Hill DJ, Roy N, Heine RG, et al. Effect of a low-allergen
maternal diet on colic among breastfed infants: a
randomized, controlled trial. Pediatrics
2005;116:e709–15.
47. Jakobsson I, Lindberg T. Cows’ milk proteins cause
infantile colic in breast-fed infants: a double-blind
crossover study. Pediatrics 1983;71:268–71.

CHAPTER

4 

Clinical Overview of Adverse Reactions
to Foods
John M. Kelso

Introduction
‘Allergy’ is the term most often used by patients to
describe an adverse reaction attributed to a food. To
an allergist, the term implies an IgE-mediated – or
at least an immunologically mediated – reaction.
Adverse reactions to foods that are not immuno­
logically mediated are best termed ‘intolerance’.1
This chapter will describe the most common
food-related complaints for which patients seek
care from an allergist because either the patient or
the referring physician believes the reaction to be
allergic. There are a host of gastrointestinal disorders, such as gastroesophageal reflux, irritable
bowel syndrome and inflammatory bowel disease,
where patients may describe symptoms in relation
to eating, but these patients are typically referred to
gastroenterologists and these conditions will not
specifically be considered here.
When a patient presents with a food-related
health complaint, the history is paramount and
dictates the differential diagnosis, appropriate
testing and treatment.1,2 The physical examination
may add some additional information if the patient
happens to be seen acutely at the time of a reaction.
There are five crucial elements to the history:
1. The suspect(s): What food(s) does the patient
believe caused the reaction(s)?
2. Timing: How long from exposure to symptom
onset?
© 2012, Elsevier Inc

3. The nature of the reaction: What are the
symptoms?
4. Reproducibility: Has it happened more than
once? Does it happen every time?
5. What treatment was administered and what
was the response?

IgE-mediated reactions
Urticarial/anaphylactic
Why is it important to determine whether or not a
reaction is IgE-mediated? IgE-mediated reactions to
foods are potentially life-threatening, and testing
and treatment are available. As many as 200 people
each year die from such reactions, and most are
preventable.3 A patient may want to avoid onions
if they cause heartburn, but if he or she eats some
accidentally, the result is discomfort. If a patient is
allergic to peanuts, however, the result of an accidental ingestion could be fatal. Knowing whether
or not a patient has a food allergy rather than a
food intolerance dictates how careful they need to
be about avoiding the food. Testing is available to
determine whether the patient has IgE antibody
specifically directed to the suspect food (see Chapter
13). Non-specific treatment in the form of oral
antihistamines and self-injectable epinephrine is
available for accidental ingestions for patients
with IgE-mediated food allergy, whereas for food

Food Allergy

intolerance these measures would be unnecessary
and unhelpful. Specific treatment in the form of
oral desensitization or induction of tolerance will
probably become an option in the near future for
IgE-mediated food allergy (see Chapter 17), but
this would not be expected to help in food
intolerance.

Suspect foods
Virtually all reported food allergy deaths have been
from one of five foods or food groups: peanuts, tree
nuts, fish/shellfish, cows’ milk and egg.4–6 Therefore, patients who are suspicious that one of these
foods has caused a reaction are more likely to have
IgE-mediated food allergy. Many other foods have
been demonstrated to cause such reactions, but
they are less likely to do so and less likely to cause
life-threatening reactions. Allergens are antigens to
which people make specific IgE antibodies. Like
most antigens, most allergens are proteins.

Timing
The timing of the reaction is critical. IgE-mediated
reactions to food typically begin within minutes to
a couple of hours after ingestion.3 It usually takes
only a small amount of the food to cause a reaction,
and the reactions generally happen with every
exposure. These conditions usually make the diagnosis obvious. Patients who present saying that
they think they are allergic to peanuts because they
have broken out in hives the last three times they
have eaten them are almost certainly allergic to
peanuts. On the other hand, patients who present
with hives and have no idea what is causing them
are very unlikely to turn out to have food allergy as
a cause. However, patients are often under the
impression that the reaction could be to something
they ate the previous day or several days before, or
something that they have been eating more of than
usual lately, when in fact, if they were allergic to the
food, the reaction would have occurred shortly
enough after each exposure to make the connection
more obvious.

Nature of reaction
The nature of the reaction suggests the likelihood
that the reaction is IgE-mediated. IgE-mediated
reactions are mast cell-mediated reactions and the
symptoms should be consistent with the release of
histamine and other mediators from mast cells.3
50

Mast cells are most abundant where we have interface with our environment, namely skin, respiratory tract and gastrointestinal tract. Histamine is
also a potent vasodilator, and thus hypotension is
another major feature of systemic IgE-mediated
allergic reactions. Therefore patients will often
describe cutaneous symptoms of flushing, itching,
swelling and/or hives. Respiratory complaints can
include the symptoms of allergic rhinitis: itchy,
watery, red eyes; itchy, runny, stuffy nose; and
sneezing. Although such symptoms are typically
brought on by exposure to an airborne allergen,
once an ingested allergen such as a food has access
to the circulation and the allergen attaches to mastcell-bound IgE in the eyes and nose, the same symptoms result. Pharyngeal complaints can include an
itchy or sore throat, or symptoms resulting from
laryngopharyngeal edema, such as the sensation of
a lump in the throat or difficulty talking, swallowing or breathing. Lower airway symptoms are those
of asthma: coughing, wheezing, shortness of breath
and chest tightness. Patients who have asthma are
more likely to have these symptoms, and such
symptoms are more likely to be severe,5 but even
patients with no history of asthma can have the
same symptoms as part of an anaphylactic reaction.
Gastrointestinal symptoms can include nausea,
vomiting, abdominal pain and diarrhea. Symptoms
of hypotension are lightheadedness or loss of consciousness. Although it would seem that gastrointestinal symptoms would be the most common
manifestation of IgE-mediated food allergy, the
most common manifestations are dermatologic,
respiratory and cardiovascular.1 Deaths from anaphylaxis are either due to asphyxia (upper laryngeal
edema or severe bronchospasm) or hypotension.7
Again, pre-existing asthma is an important risk
factor for a fatal outcome from an anaphylactic
episode.4,5

Reproducibility
Most patients assume that one must be born with
food allergy and that it persists for a lifetime. Therefore, they believe that if they have eaten a food
uneventfully many times in the past that they
cannot be allergic to it. In reality, because as with
any other IgE-mediated reaction prior exposure is
required for sensitization, patients must have had
some previous uneventful exposure to become
allergic. This previous exposure is most often actually consuming the food, but can also be through

Clinical Overview of Adverse Reactions to Foods

less obvious sources, particularly in children.
Whenever a lactating mother eats any food, some
of that food protein is present in the breast milk for
several hours afterwards.8 Food proteins are present
on household surfaces such as countertops and
may become airborne, so cutaneous and respiratory
exposures may occur.9 Many foods have immunological cross-reactivity with other foods, and prior
exposure may have been to such a food sharing
similar proteins.10 Thus patients may appear to have
an allergic reaction on their first exposure to a food,
but in fact they have had prior relevant allergen
exposure.8 This prior exposure was sufficient to
cause sensitization (i.e. specific IgE antibody production) but not a clinical reaction. Once sensitized, a subsequent exposure to a larger amount
causes an allergic reaction.
Once sensitized, an allergic reaction typically
occurs with each ingestion. Thus, it is uncommon
for patients to react to the ingestion of a food on
one occasion but not the next. Similarly, although
there may be a dose–response curve where eating
more of the food is more likely to cause a reaction
or more likely to cause a severe reaction, this is
usually not apparent clinically because such a small
amount causes an obvious reaction. Therefore it is
uncommon for patients with an IgE-mediated food
allergy to report that they can tolerate a small
portion of a suspect food but not a large portion.
Therefore, although it is certainly important to
inquire what has happened with the ingestion of
the suspect food prior to the ingestion that appeared
to have caused a reaction, it is even more helpful
to know what has happened with subsequent ingestions. Many patients will have avoided the suspect
food after an apparent reaction, but some have not.
If the patient can relate that they have consumed
the suspect food uneventfully since the apparent
reaction, this markedly reduces the likelihood that
they are allergic to the food.
There are exceptions to the general rule that, once
sensitized, a patient will react to each subsequent
exposure to a food. Occasionally some cofactor is
required to cause a clinical reaction. These cofactors
include exercise, consumption of alcohol and the
ingestion of medications known to cause or lower
the threshold for mast cell degranulation, such as
non-steroidal anti-inflammatory drugs (NSAIDs)
or narcotic analgesics.11–13 Thus, a patient who has
made IgE antibodies to a food may still be able to
eat that food without reaction. However, if they eat
the food and then exercise, or eat the food while

4

taking an NSAID or narcotic, the combination will
cause a reaction.

Previous treatment and response
to treatment
A final element of the history that can be helpful is
determining what treatment was given for previous
reactions and whether or not it was helpful. A rash
that responded promptly to the administration of
an oral antihistamine, or lightheadedness that
resolved soon after the administration of epinephrine, would be consistent with the reaction being
IgE mediated.

Testing
If the history is consistent with a potentially IgEmediated reaction, demonstrating the presence of
IgE antibody to the food is essential.1 Although
a patient with a classic history is in fact likely to
be allergic to the suspect food, testing is required
to make a diagnosis. Occasionally an ‘obvious’
allergic reaction to a food turns out to be a nonIgE-mediated reaction, a coincidence, or an IgEmediated reaction to another food consumed at the
same time. As with all allergy testing, allergy testing
for foods should not be done as a screening test, or
in the absence of a history or disease that suggests
a possible reaction to the food (see Chapter 13).

Skin test vs RAST
There are two methods to look for IgE antibody,
skin testing and in-vitro assays of serum for specific
IgE antibodies.1,2 The blood tests are commonly
referred to as RASTs (radioallergosorbent tests),
although RAST is actually a brand name that has
become generic to refer to any of the assays for
specific IgE antibody, such as ImmunoCAP, Immulite and Turbo RAST, most of which no longer use
radioactive isotopes for detection. Skin tests have
the advantage of the results being available quickly,
as they are read 15 minutes after placing and can
therefore be available at the same visit when the
history was taken, whereas RAST results are typically available only days after being drawn and
require an additional visit or follow-up phone call
to discuss them. RASTs are also typically more
expensive. Systemic allergic reactions may rarely
occur with skin testing, although vasovagal reactions are just as likely14 and may also occur with
51

Food Allergy

blood drawing. Patients must be off all antihistamines (oral and topical), including medications
with antihistaminic activity such as tricyclic antidepressants, for 5–7 days prior to skin testing,15
whereas these medications do not interfere with
RASTs. Skin tests are also generally more sensitive
than RASTs, meaning that they are more likely to
be positive when IgE antibody is present, although
the currently available in vitro assays are nearly as
sensitive. In most cases the skin test and RAST
results would agree, i.e. both are positive or both
are negative. When there is a discrepancy, the majority are a positive skin test and negative RAST,
although occasionally the reverse is true.15

Positive vs negative
As with any assay, there is some level of result that
is considered positive, i.e. distinguishable from
background or negative results. For skin prick tests
the most commonly used criteria are a 3 mm wheal
greater than an appropriate negative control and
10 mm erythema.1 For RAST assays that quantify
specific IgE antibody the cutoff is usually 0.1 or
0.35 kU/L (see Chapter 13).

False positives
Whether detected by skin test or RAST, the presence
of IgE antibody does not equate to clinical allergy.
As is the case with all IgE-mediated diseases, including allergic rhinitis, allergic asthma and allergic
reactions to drugs and stinging insects, not all
patients who make IgE antibody to a food will react
when they eat that food.16 The reasons for this phenomenon of clinically irrelevant positive IgE tests
are not well characterized. The higher the level of
specific IgE antibody to a food, the more likely it is
that the patient will react if they eat that food.
However, there are patients who have very high
levels of IgE to a food yet nonetheless consume it
without reaction. Also, although there is a correlation between how much allergic antibody is present
and the likelihood of a reaction, there is little correlation between the level of IgE antibody and the
severity of that reaction.2,16 It may be that the particular IgE antibodies that a patient made to a food,
albeit few, are nonetheless more likely to cause a
reaction because they bind the allergen with greater
avidity, or bind more clinically relevant epitopes.
As above, the lower the level of IgE antibody, the
less likely the patient is to react, but this correlation
52

is not perfect, i.e. occasional patients with high
levels will tolerate the food, whereas occasional
patients with low levels have severe reactions. For
some foods, a certain level of IgE antibody as measured by RAST or skin test has been correlated with
the probability of reacting or not reacting to the
food if consumed.16 These are most often referred
to as ‘cutoff’ values and are better characterized for
the probability of reacting to a food, i.e. positive
predictive values. For example, if the measured
amount of IgE for a certain food is above a certain
level, there is a 95% chance that a patient would
react if they consumed that food.2 There are some
data on negative predictive values as well, i.e. the
probability that the patient will not react to the
food. For example, if the measured amount of IgE
for a certain food is below a certain level, there is a
95% chance that a patient would not react if they
consumed the food.16 Also, for some foods the
levels of IgE antibody that correlates to a 50%
chance of reacting to the food have been reported.17
It is important to realize that there are limits to the
generalizability of the use of these cutoff values.
Different studies have reported different values,
probably because different patient populations and
different assay methods were used, but they nonetheless provide a useful guide.

False negatives
Although RAST and skin tests are quite sensitive,
they are not perfect. There are patients with a history
of food reactions who have negative tests for IgE
antibody but nonetheless react when re-exposed to
the food. If there is a strong clinical suspicion of an
IgE-mediated reaction to a food and a test for IgE
antibody is negative, it is important to perform
additional testing before concluding that the patient
is not allergic. If a patient’s skin test result is negative, it may be appropriate to do a RAST, or vice
versa. If the skin test with a commercial extract of
a food is negative, it may be appropriate to create a
crude extract made from the actual food. This is
often required in the case of allergy to fruits and
vegetables, where many of the allergens are quite
labile.1 For example, a patient who reports itching
of the mouth with apple ingestion may well have a
negative RAST and skin test with commercial extract,
yet have a clearly positive test result when the skin
test is performed with the juice from a fresh apple.
This is less often the case with the food allergens
most likely to cause anaphylaxis, i.e. milk, egg, tree

Clinical Overview of Adverse Reactions to Foods

nuts, fish/shellfish and legumes (especially peanut),
although occasionally patients with a history of
reacting to these foods will react only to a skin test
with an extract made from the actual fresh food.

Challenge
The ultimate clinical diagnostic test for food allergy
is what happens when the patient consumes the
actual food. A patient with a recent history of an
allergic reaction to a food and a large positive skin
test or highly positive RAST to that food would
almost certainly react if they were to eat the food.
On the other hand, a patient with a distant history
of an allergic reaction to a food and a negative or
small positive skin test or low positive RAST to that
food might very well not react if they were to eat
the food. Patients who can report that they regularly eat a food without reaction are not allergic to
that food, irrespective of skin test or RAST results
(an exception is atopic dermatitis, as below).
Patients who have been trying to avoid a food may
nonetheless have accidental ingestions and can
report whether or not they reacted. Patients who
have successfully avoided the ingestion of a food
will not be able to provide this information and
at some point may be candidates for an oral
challenge under observation. In research settings,
these are most often done as double-blind, placebocontrolled food challenges (DBPCFC), whereas in
clinical practice they are most often performed as
open, oral food challenges.2 By definition, the challenges have a chance of inducing a life-threatening
anaphylactic reaction and must be performed in a
setting where there are medical personnel and
equipment available to recognize and treat such a
reaction should it occur (see Chapter 14).

4

there is a smaller amount of the protein and/or
because it has been cooked at a high temperature
for a long time, which may lead to a denaturation
of the relevant allergens in these foods. Although
this phenomenon has been confirmed by research
studies in a majority of milk- and egg-allergic children, it should be noted that in the minority of
such children who do not tolerate the foods even
in baked goods, their reaction to these baked goods
can be severe.19,20 Although one might wonder
whether allowing such exposure in children who
tolerate it might delay or prevent their ultimately
outgrowing their allergy, studies have indicated that
this exposure may actually hasten the resolution of
the allergy.21

Treatment
The treatment for food allergy is to avoid ingestion
of the relevant food allergen and to be prepared to
treat an allergic reaction if it occurs following an
accidental ingestion.

Avoidance
Patients allergic to a food must be vigilant.2 They
must carefully read packaged food labels and
re-read them every time the food is purchased, since
the ingredients may have changed even if the overall
appearance of the package has not. They must ask
questions directly and repeatedly to hosts and food
servers about the contents of prepared food. They
must make clear that they are asking whether or not
a dish contains a food because they have a potentially life-threatening allergy to that food, not
simply because they do not care for the taste of the
food or wish to avoid it for some other reason (see
Chapter 16).

Natural history

Emergency treatment

Some food allergies, such as reactions to cows’ milk
and egg, are commonly ‘outgrown’, i.e. they resolve
spontaneously over a period of time. Others, such
as reactions to peanuts, tree nuts, and fish/shellfish
are usually lifelong and less likely to be ‘outgrown’.1
There are exceptions, however, as egg or milk allergy
occasionally persists into adulthood, and perhaps
as many as 20% of toddlers with peanut allergy will
outgrow it.18 Many parents report that their milk- or
egg-allergic children react if they eat these foods
directly, but tolerate them if they are in baked
goods, such as cakes.19,20 This is presumably because

Despite these attempts at avoidance, the majority
of food allergy deaths occur in patients who knew
they were allergic to the food5 but had an accidental
ingestion, usually because the food was ‘hidden’ in
some other food, or a packaged food was contaminated by a food allergen not declared on the label.22
Therefore, each and every time a food-allergic
patient is eating, medications to treat a reaction,
namely self-injectable epinephrine and an antihistamine, must be immediately available.1 If they
know they have had such an accidental ingestion
they should also take the antihistamine and be
53

Food Allergy

prepared to use the self-injectable epinephrine.
When to use the self-injectable epinephrine requires
some judgment and depends on the nature of previous reactions. Although there are exceptions,
most systemic allergic reactions are stereotypic, i.e.
the nature and severity of the reaction in the past
is likely to be the nature and severity of future reactions.23 Thus, in a patient who has suffered a truly
life-threatening reaction to a food in the past and
had an accidental ingestion, the epinephrine should
be used even before the onset of any symptoms. On
the other hand, in a patient who has never had
more than cutaneous reactions with previous ingestions, it may be reasonable to administer the
antihistamine and prepare to administer the epinephrine. If at any stage of the reaction, whether the
antihistamine has been administered or not, if the
patient develops any respiratory symptoms (i.e. not
just frank respiratory distress, but any amount of
cough, wheeze, shortness of breath or throat swelling or clearing) or any cardiovascular symptoms
(i.e. not just frank syncope, but any amount of
lightheadedness) or repeated emesis, the epinephrine should be administered. Once the epinephrine has been administered, even if the patient
appears to be responding favorably, they should be
transported to the nearest emergency department
(ED). If the historical or current reaction seems
truly life-threatening, it is appropriate to call the
emergency medical services (EMS). Although epinephrine is typically very effective in treating anaphylactic reactions, its effect may also be temporary and
repeat doses may be required.24 Consideration can
be given to prescribing multiple doses of epinephrine,24–26 especially if prior reactions have been
severe or medical facilities are far away. Reactions
may progress to require additional treatment such
as oxygen, intravenous fluids, and intubation or
tracheotomy. Even if an ED is close by, patients who
know they are suffering an allergic reaction to an
accidental food ingestion of sufficient severity to
warrant the ED visit should administer the epinephrine before going to the ED.

The choice of antihistamine
An antihistamine for use in an acute allergic reaction to a food should have a rapid onset of action.
It should also be available in a form convenient for
patients to carry with them, since it needs to be
immediately available whenever and wherever they
are eating. Syrup for small children and rapidly
54

dissolving tablets that can be taken without liquids
are best suited for this purpose. Although the
number of doses to be used in this circumstance
would be expected to be small, an inexpensive
generic formulation would also be preferable.
Diphenhydramine has traditionally been the
antihistamine of choice for the treatment of acute
allergic reactions because of its rapid onset of
action, ability to be administered by oral, intravenous and intramuscular routes, availability in
capsule, syrup and rapidly dissolving tablet formulations, and its use in published protocols. It is
available as an inexpensive generic.
Cetirizine is a reasonable alternative. It has an
onset of action as fast as diphenhydramine, and is
also available in syrup and rapidly dissolving tablet
formulations. It has the advantage of having a
longer duration of action and less sedative potential
than diphenhydramine. It is also available as an
inexpensive generic form.

The choice of self-injectable epinephrine
There are three branded (EpiPen, Twinject and
Adrenaclick) and one generic epinephrine autoinjectors currently on the market. Each has advantages
and disadvantages.26 Insurance coverage, cost, ease
of carrying (weight and size), ease of use, possible
need to carry two doses, and patient preference all
must be factored into which device to prescribe.
Each EpiPen, Adrenaclick or generic autoinjector
delivers one 0.3 mg or 0.15 mg dose (EpiPen Jr.)
of epinephrine as an autoinjector. Each Twinject
delivers one 0.3 mg or one 0.15 mg dose as an
autoinjector and in addition can be dismantled to
reveal the syringe; after removal of a collar on the
plunger, this syringe with attached needle can be
used to administer a second dose of epinephrine in
the same milligram quantity as the first dose.

One dose or two
Studies of anaphylactic reactions in general and
food-induced anaphylactic reactions in particular
suggest that in a sizeable minority of reactions a
second dose of epinephrine is required to treat a
reaction.25 It may be appropriate for patients who
have suffered severe reactions in the past, or who
are further away from emergency medical facilities,
to carry two doses of self-injectable epinephrine
with them at all times. This can be accomplished
by carrying two single autoinjectors or one

Clinical Overview of Adverse Reactions to Foods

Twinject. Although it is more convenient to carry
the single Twinject device, the technical aspects of
using the second dose from the Twinject might
cause some patients to prefer carrying two single
autoinjectors.26

Oral immunotherapy
Immunotherapy by subcutaneous injection is a
well-established and effective treatment for allergic
rhinitis, allergic asthma and stinging insect allergy.
It is possible that such treatment would be effective
for food allergy as well. Studies with peanut injection immunotherapy demonstrated some improvement in the amount of oral peanut ingestion
patients could tolerate without reaction, but systemic reactions to the injections were very common
and precluded patients from being maintained at
an effective maintenance dose.27 Immunotherapy
with altered peanut proteins that are less allergenic
but still antigenic is being explored.28
Several studies have now shown promise with oral
immunotherapy for food allergy.19–21,29–35 Most of
these studies have been with cows’ milk and egg, but
studies with peanut have also been reported.
Although milk and egg allergies are commonly outgrown, for those children who do not outgrow them,
they continue to pose the burden of food avoidance
and the risk of accidental ingestion. Oral immunotherapy for food, sometimes called specific oral tolerance induction, involves protocols where allergic
patients are orally administered a minuscule amount
of the food initially, e.g. one drop of a solution made
by putting 10 drops of milk in 100 mL of water, and
then progressively higher amounts over days to
months. Some of the protocols involve administration in an observed setting (clinic or hospital) for
the initial doses, or when the dose is increased.
Reactions to the food ‘doses’ can cause systemic
reactions, and providers and patients or families
need to be prepared to recognize and treat anaphylaxis. Some patients who have completed these protocols have been able to tolerate an unlimited
amount of the food, whereas others only tolerate
enough to allow them not to react to a small amount
of the food, such as might occur in an accidental
ingestion. It is unclear whether oral desensitization
to food results in permanent desensitization or tolerance, such as might occur to pollen after successful
immunotherapy has been discontinued, where
intermittent contact with the allergen does not result
in symptoms, or whether there is only a temporary

4

desensitization or tolerance, such as occurs with
penicillin desensitization, where ongoing exposure
to the allergen is required to maintain the desensitized state. Most of the oral food desensitization
protocols require daily ingestion of the food. In
studies that have achieved successful oral desensitization, where patients are tolerating daily ingestion
of the food, some have had the patients avoid the
food again for a period of months and then
re-challenged them. Some such patients do not react
and appear to have achieved a long-term tolerance,
whereas others do react and appear to have lost their
tolerance (see Chapter 14).31,33

Food-dependent, exercise-induced
anaphylaxis
As mentioned above, some patients with IgEmediated food allergy do not react to the ingestion
of the food alone, but would react if they ate the
food and then subsequently exercised.11,36 The
reason for this is unclear, although it seems possible that the exercise alters the absorption or distribution of the food allergen systemically or renders
mast cells more susceptible to degranulation. The
foods that have been associated with this phenomenon include the common food allergens (cows’
milk, egg, tree nuts, fish/shellfish and legumes, primarily peanut), but have also involved other foods
such as wheat or celery. As an exception to the
general rule that allergy testing should not be done
in the absence of a history of reacting to the food,
in the case of food-dependent exercise-induced
anaphylaxis the history is not obvious, because
when the patient consumes the food without exercise afterward they do not react, and so would not
think of themselves as being allergic to the food.
Thus, even in the absence of any suspicion of food
allergy, patients with a history of exercise-induced
anaphylaxis should be tested to all food they eat.37
If a culprit food is identified, the patient needs to
avoid ingesting that food only if they are going to
exercise within a few hours afterward. There are
some patients with this syndrome who appear to
have anaphylaxis if they exercise too soon after
eating any food, and they need to avoid eating
anything too close to the time of exercising –
typically 2–4 hours. All patients with exerciseinduced anaphylaxis should be counseled to not
exercise alone, to stop exercising at the first sign of
a reaction, and to have self-injectable epinephrine
available to treat a reaction.
55

Food Allergy

Food allergy causing exacerbation
of eczema
About one-third of children with difficult to control
eczema have food allergy as an exacerbating
factor.38,39 Unlike urticarial or anaphylactic reactions to foods, when the ingestion of a food exacerbates eczema it may not be obvious because the
skin condition is already present.38 The foods that
most often exacerbate eczema are the same as those
that cause anaphylaxis (milk, egg, tree nuts, fish/
shellfish and legumes, primarily peanut), but other
foods can do so as well.38,39 Thus patients with difficult to control eczema should have skin tests or
RASTs for the common food allergens as well as any
foods the patient or family suspect of worsening the
eczema. Foods that give negative test results are not
exacerbating the eczema. The likelihood that a food
giving a positive test result is exacerbating the
eczema is overall about one-third.38,39 The size of
the skin test or the level of specific IgE antibody on
the RAST can be used to determine the chance that
a particular food is a factor. Not surprisingly, the
higher the test result, the more likely the clinical
relevance, with 95% positive and negative predictive value cutoff levels established for some foods,
as above.16 If there is uncertainty that ingestion of
a particular food is exacerbating the eczema, it may
be appropriate to exclude that food from the diet
for a few weeks to see if the eczema improves. If so,
the food should continue to be avoided. If not, it
can be added back to the diet. There are rare case
reports of anaphylaxis when foods have been added
back to the diet in this situation, and consideration
can be given to doing this under observation.40

Pollen-food allergy syndrome (oral
allergy syndrome)
Some patients with allergic rhinitis due to grass, tree
or weed pollen will report that if they eat certain
fresh fruits or vegetables, or occasionally nuts, they
get itching in the mouth.41,42 This pollen–food
allergy syndrome has also been known as oral allergy
syndrome because the symptoms rarely progress
beyond oral itching, although more severe swelling
of the tongue or throat or other symptoms of anaphylaxis can develop.43 Although the pollens and
foods are not botanically related, they nonetheless
contain common cross-reacting protein allergens.
Common examples are ragweed and melons, birch
and apple, and mugwort and celery. Thus patients
56

who have been sensitized via the respiratory route
to a specific pollen may react when they eat a food
containing the same protein. The particular proteins
responsible for this phenomenon are quite labile,
i.e. easily broken down. This probably explains why
the symptoms are usually confined to the mouth,
and why the foods can almost invariably be eaten
cooked without any reaction. It also probably
explains why skin tests with commercial extracts and
RASTs with fresh fruits and vegetables are often
negative in these patients, but skin tests performed
with the juice from the fresh food are positive.
Unlike food allergy causing urticarial or anaphylactic reactions, in the case of pollen–food allergy syndrome patients are typically told that they can
continue to eat the food if they desire, as long as the
symptoms do not go beyond oral itching. Occasionally patients with pollen–food allergy syndrome
have more severe, systemic allergic reactions and
must completely avoid the food.42 Given the crossreactivity between the pollens and foods, there is
reason to believe that standard immunotherapy
with pollens could, in addition to alleviating allergic
rhinitis symptoms, also alleviate the associated
food allergy symptoms, and published studies have
reported some success with this therapy.44,45

Other allergic reactions to foods related
to airborne allergens
Some patients who are allergic to natural rubber
latex are also allergic to certain foods due to crossreacting allergens.46 The food allergies most often
associated with latex allergy are banana, avocado,
kiwi and chestnut, but many other foods have also
been associated.
There are a number of reports of patients who
were sensitized to dust mites and then consumed
baked goods made with flour contaminated by
mites, suffering anaphylactic reactions as a result of
ingesting mite allergens.47–49
Some nurses with a history of respiratory exposure to psyllium as a result of dispensing psylliumcontaining laxatives, have later had anaphylactic
reactions when they consumed psyllium-containing
breakfast cereals.50–52

Eosinophilic esophagitis
In eosinophilic esophagitis, a new or at least newly
recognized condition, there is a significant eosinophilic inflammatory response in the esophagus.53

Clinical Overview of Adverse Reactions to Foods

The resulting inflammation leads to dysphagia. The
condition can develop at any age from infancy to
adulthood, and is more common in those with
other atopic diseases, i.e. asthma, atopic dermatitis,
allergic rhinitis and food allergy. The diagnosis is
made by esophagoscopy, which can reveal characteristic gross abnormalities including furrows and
rings. The esophagus may also appear normal, and
biopsy is essential. The presence of more than 20
eosinophils per high-powered field, particularly in
the proximal esophagus, is characteristic. The relationship to food allergy is unclear. An elemental
diet is curative, implying that food ingestion is
causative.54 Some investigators have had success
eliminating foods to which the patients make IgE
antibody, although such patients do not have urticarial or anaphylactic reactions to the foods.55
Others have empirically eliminated certain highly
allergenic food groups, with improvement in the
condition. In addition to detecting possible culprit
foods by testing for IgE antibody with skin tests or
RASTs, additional causative foods have been determined by some researches by patch testing with the
foods.55 In patients in whom food elimination diets
are not successful or feasible, treatment with swallowed corticosteroids has been successful.56 These
are not simply oral corticosteroids, but rather corticosteroids intended for inhalation for asthma,
which are instead swallowed in a formulation that
allows them to coat the esophagus and yet minimize systemic absorption. Finally, in patients whose
disease is not responsive to these measures, treatment with anti-IL-5 antibodies (IL-5 activates and
prolongs the survival of eosinophils) has been used
with some success (see Chapter 10).57

Non-IgE-mediated reactions
Lactose intolerance
Perhaps the most common non-IgE-mediated reaction to food is lactose intolerance or lactase deficiency.58 Human milk contains lactose and human
infants produce the enzyme lactase to digest it.
Many humans normally undergo a large decline in
lactase production after infancy and subsequently
develop gastrointestinal symptoms of nausea,
cramping, bloating and diarrhea if they consume
lactose-containing foods (dairy products). The condition is much more common in Asians and
African-Americans, and is probably best thought of

4

as a variation of normal rather than a disease. For
patients who are lactose intolerant who wish to
consume dairy products, lactase supplementation
allows them to do so without symptoms.

Celiac disease
A well-characterized immune- but not IgE-mediated
reaction to food is celiac disease (also called glutensensitive enteropathy or non-tropical sprue).59,60
Gluten is a mixture of proteins found in the cereal
grains wheat, rye and barley. In wheat, gluten is a
mixture of gliadin and glutenin. In some persons
with HLA-DQ2 or HLA-DQ8 the ingestion of gluten
produces an immune response including IgA antibodies against tissue transglutaminase (TTG). The
resulting inflammation in the intestines leads to
diarrhea and other gastrointestinal symptoms.
Therefore, in patients who report gastrointestinal
symptoms in association with the ingestion of
wheat, testing for celiac disease should be considered. Serology for IgA anti-TTG antibodies is
perhaps the most appropriate test. For the test to be
accurate the patient must be consuming gluten and
must not be IgA deficient (more common in celiac
disease). HLA typing has a very high negative predictive value, i.e. the absence of HLA-DQ2 and
HLA-DQ8 virtually excludes the diagnosis, but a
very low positive predictive value as most people
who have these HLA types do not have celiac
disease.

Non-IgE-mediated food protein
reactions in infancy
There are a number of food protein-induced illnesses of infancy that are not IgE mediated but
which are probably immune mediated (see Chapter
11 for more details). These reactions most often
occur to milk protein, but can be caused by other
foods as well. Most are outgrown by the age of 1 or
2 years.

Food protein-induced enterocolitis
syndrome
Food protein-induced enterocolitis syndrome
(FPIES) is a rather dramatic and serious reaction to
food proteins61,62 in which, a couple of hours after
food ingestion, infants develop vomiting, diarrhea,
hypotension and lethargy. A blood count often
reveals a high white count and neutrophilia.
57

Food Allergy

Patients are often evaluated and treated for sepsis.
The association to the food may not be recognized
at first because of the delay between ingestion and
the onset of symptoms. FPIES has been reported in
association with milk and soy formulas, as well as
solid foods including cereal grains, legumes and
meats. Treatment consists of avoiding the suspect
foods, which can typically be reintroduced by age
3 without symptoms.

Dietary protein-induced proctitis
Dietary protein-induced proctitis describes bloodtinged stools in otherwise healthy infants caused by
ingestion of milk- or soy-based formulas or food
proteins in breast milk.63 There are no confirmatory
tests. Suspect foods are eliminated until the blood
in the stools resolves. The foods can typically be
reintroduced uneventfully at age 1 or 2 years.

Scombroid poisoning
After the ingestion of fish, some persons experience
systemic reactions, including flushing, hives, gastrointestinal complaints, dyspnea and hypotension,
that seem allergic but which are instead due to
scombroid poisoning.64 The fish are usually of the
family Scombridae, which includes tuna and mackerel. Histamine has been demonstrated to be the
causative agent: the fish involved contain histidine,
which is metabolized to histamine by bacteria in
inadequately refrigerated fish.65 The diagnosis is
more likely if others who consumed the same fish
had similar symptoms. Skin tests with commercial
fish skin test extracts would be negative, whereas a
skin test with the suspect fish, if available, would
be positive.66

IgG food tests
It is quite common for patients to present with
laboratory test results for IgG antibodies to foods.
These are often performed by alternative medicine
practitioners who claim that the foods to which
patients make IgG antibodies as demonstrated by
these tests are the cause of a whole host of symptoms, not only gastrointestinal complaints, but also
fatigue, joint pains and difficulty concentrating. The
production of IgG antibodies to foods, however, is
a normal immune response.67 Everyone makes
these antibodies and they do not cause adverse
reactions. IgG food assays should not be ordered,
and patients who have already had them performed
58

should be counseled as above that they are a normal
immune response to food, are present in all individuals, and do not cause illness. Patients may have
a great deal of psychological and monetary investment in the tests and be skeptical of the notion that
they do not mean something. As with any such
unconventional testing or treatment, the ultimate
goal is for the patient to feel well, and if they feel
better not eating a particular food and are still able
to have a nutritionally complete and enjoyable diet,
then they can certainly do so.

The Food Allergy and
Anaphylaxis Network
The Food Allergy and Anaphylaxis Network (FAAN)
is an organization of patients and families affected
by food allergy. They provide accurate, practical
information to those dealing with food allergy –
everything from recipes to food recalls for allergen
contamination, to how to deal with school, day
care, camp etc. – in relation to protecting foodallergic patients from life-threatening reactions.
Information can be found at www.foodallergy.org.
Patients and families with food allergy should be
referred to this valuable resource.

References
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2. Sicherer SH, Sampson HA. Food allergy. J Allergy Clin
Immunol 2010;125:S116–25.
3. Sampson HA. Anaphylaxis and emergency treatment.
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4. Yunginger JW, Sweeney KG, Sturner WQ, et al. Fatal
food-induced anaphylaxis. JAMA 1988;260:1450–2.
5. Sampson HA, Mendelson L, Rosen JP. Fatal and
near-fatal anaphylactic reactions to food in children
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6. Pumphrey RS. Lessons for management of anaphylaxis
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13. Harada S, Horikawa T, Ashida M, et al. Aspirin
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16. Sampson HA, Ho DG. Relationship between foodspecific IgE concentrations and the risk of positive food
challenges in children and adolescents. J Allergy Clin
Immunol 1997;100:444–51.
17. Perry TT, Matsui EC, Kay Conover-Walker M, et al. The
relationship of allergen-specific IgE levels and oral food
challenge outcome. J Allergy Clin Immunol 2004;114:
144–9.
18. Fleischer DM. The natural history of peanut and tree
nut allergy. Curr Allergy Asthma Rep 2007;7:175–81.
19. Nowak-Wegrzyn A, Bloom KA, Sicherer SH, et al.
Tolerance to extensively heated milk in children with
cow’s milk allergy. J Allergy Clin Immunol 2008;122:
342–7, 7 e1–2.
20. Lemon-Mule H, Sampson HA, Sicherer SH, et al.
Immunologic changes in children with egg allergy
ingesting extensively heated egg. J Allergy Clin
Immunol 2008;122:977–83 e1.
21. Konstantinou GN, Giavi S, Kalobatsou A, et al.
Consumption of heat-treated egg by children allergic
or sensitized to egg can affect the natural course of egg
allergy: hypothesis-generating observations. J Allergy
Clin Immunol 2008;122:414–5.
22. Puglisi G, Frieri M. Update on hidden food allergens
and food labeling. Allergy Asthma Proc
2007;28:634–9.
23. Reisman RE. Natural history of insect sting allergy:
relationship of severity of symptoms of initial sting
anaphylaxis to re-sting reactions. J Allergy Clin
Immunol 1992;90:335–9.
24. Rudders SA, Banerji A, Corel B, et al. Multicenter Study
of Repeat Epinephrine Treatments for Food-Related
Anaphylaxis. Pediatrics 2010;125:e711–8.
25. Jarvinen KM, Sicherer SH, Sampson HA, et al. Use of
multiple doses of epinephrine in food-induced
anaphylaxis in children. J Allergy Clin Immunol
2008;122:133–8.
26. Kelso JM. A second dose of epinephrine for
anaphylaxis: how often needed and how to carry.
J Allergy Clin Immunol 2006;117:464–5.

4

27. Nelson HS, Lahr J, Rule R, et al. Treatment of
anaphylactic sensitivity to peanuts by immunotherapy
with injections of aqueous peanut extract. J Allergy
Clin Immunol 1997;99:744–51.
28. Sicherer SH, Sampson HA. Peanut allergy: emerging
concepts and approaches for an apparent epidemic.
J Allergy Clin Immunol 2007;120:491–503; quiz 4–5.
29. Patriarca G, Nucera E, Roncallo C, et al. Oral
desensitizing treatment in food allergy: clinical and
immunological results. Aliment Pharmacol Ther
2003;17:459–65.
30. Meglio P, Bartone E, Plantamura M, et al. A protocol
for oral desensitization in children with IgE-mediated
cow’s milk allergy. Allergy 2004;59:980–7.
31. Buchanan AD, Green TD, Jones SM, et al. Egg oral
immunotherapy in nonanaphylactic children with egg
allergy. J Allergy Clin Immunol 2007;119:199–205.
32. Burks AW, Jones SM. Egg oral immunotherapy in
non-anaphylactic children with egg allergy: follow-up.
J Allergy Clin Immunol 2008;121:270–1.
33. Staden U, Rolinck-Werninghaus C, Brewe F, et al.
Specific oral tolerance induction in food allergy in
children: efficacy and clinical patterns of reaction.
Allergy 2007;62:1261–9.
34. Longo G, Barbi E, Berti I, et al. Specific oral tolerance
induction in children with very severe cow’s milkinduced reactions. J Allergy Clin Immunol 2008;121:
343–7.
35. Skripak JM, Nash SD, Rowley H, et al. A randomized,
double-blind, placebo-controlled study of milk oral
immunotherapy for cow’s milk allergy. J Allergy Clin
Immunol 2008;122:1154–60.
36. Du Toit G. Food-dependent exercise-induced
anaphylaxis in childhood. Pediatr Allergy Immunol
2007;18:455–63.
37. Guinnepain MT, Eloit C, Raffard M, et al. Exerciseinduced anaphylaxis: useful screening of food
sensitization. Ann Allergy Asthma Immunol
1996;77:491–6.
38. Sampson HA. Jerome Glaser lectureship. The role of
food allergy and mediator release in atopic dermatitis.
J Allergy Clin Immunol 1988;81:635–45.
39. Burks AW, Mallory SB, Williams LW, et al. Atopic
dermatitis: clinical relevance of food hypersensitivity
reactions. J Pediatr 1988;113:447–51.
40. David TJ. Anaphylactic shock during elimination diets
for severe atopic eczema. Arch Dis Child 1984;59:
983–6.
41. Mari A, Ballmer-Weber BK, Vieths S. The oral allergy
syndrome: improved diagnostic and treatment
methods. Curr Opin Allergy Clin Immunol 2005;5:
267–73.
42. Kelso JM. Pollen-food allergy syndrome.[comment].
Clinical & Experimental Allergy 2000;30:905–7.
43. Kelso JM. Oral allergy syndrome? J Allergy Clin
Immunol 1995;96:275.
44. Kelso JM, Jones RT, Tellez R, et al. Oral allergy
syndrome successfully treated with pollen
immunotherapy. Ann Allergy Asthma Immunol
1995;74:391–6.
59

Food Allergy
45. Asero R. Effects of birch pollen-specific immunotherapy
on apple allergy in birch pollen-hypersensitive patients.
Clin Exp Allergy 1998;28:1368–73.
46. Condemi JJ. Allergic reactions to natural rubber latex at
home, to rubber products, and to cross-reacting foods.
J Allergy Clin Immunol 2002;110:S107–10.
47. Erben AM, Rodriguez JL, McCullough J, et al.
Anaphylaxis after ingestion of beignets contaminated
with Dermatophagoides farinae. J Allergy Clin
Immunol 1993;92:846–9.
48. Blanco C, Quiralte J, Castillo R, et al. Anaphylaxis after
ingestion of wheat flour contaminated with mites. J
Allergy Clin Immunol 1997;99:308–13.
49. Sanchez-Borges M, Capriles-Hulett A, Fernandez-Caldas
E, et al. Mite-contaminated foods as a cause of
anaphylaxis. J Allergy Clin Immunol 1997;99:738–43.
50. Lantner RR, Espiritu BR, Zumerchik P, et al.
Anaphylaxis following ingestion of a psylliumcontaining cereal. JAMA 1990;264:2534–6.
51. James JM, Cooke SK, Barnett A, et al. Anaphylactic
reactions to a psyllium-containing cereal. J Allergy Clin
Immunol 1991;88:402–8.
52. Freeman GL. Psyllium hypersensitivity. Ann Allergy
1994;73:490–2.
53. Blanchard C, Wang N, Rothenberg ME. Eosinophilic
esophagitis: pathogenesis, genetics, and therapy.
J Allergy Clin Immunol 2006;118:1054–9.
54. Kelly KJ, Lazenby AJ, Rowe PC, et al. Eosinophilic
esophagitis attributed to gastroesophageal reflux:
improvement with an amino acid-based formula.
Gastroenterology 1995;109:1503–12.
55. Spergel JM, Andrews T, Brown-Whitehorn TF, et al.
Treatment of eosinophilic esophagitis with specific
food elimination diet directed by a combination of
skin prick and patch tests. Ann Allergy Asthma
Immunol 2005;95:336–43.

60

56. Aceves SS, Bastian JF, Newbury RO, et al. Oral viscous
budesonide: a potential new therapy for eosinophilic
esophagitis in children. Am J Gastroenterol
2007;102:2271–9; quiz 80.
57. Stein ML, Collins MH, Villanueva JM, et al. Anti-IL-5
(mepolizumab) therapy for eosinophilic esophagitis. J
Allergy Clin Immunol 2006;118:1312–9.
58. Perino A, Cabras S, Obinu D, et al. Lactose
intolerance: a non-allergic disorder often managed
by allergologists. Eur Ann Allergy Clin Immunol
2009;41:3–16.
59. Green PH, Jabri B. Coeliac disease. Lancet 2003;362:
383–91.
60. van Heel DA, West J. Recent advances in coeliac
disease. Gut 2006;55:1037–46.
61. Sicherer SH. Food protein-induced enterocolitis
syndrome: case presentations and management lessons.
J Allergy Clin Immunol 2005;115:149–56.
62. Mehr S, Kakakios A, Frith K, et al. Food proteininduced enterocolitis syndrome: 16-year experience.
Pediatrics 2009;123:e459–64.
63. Ravelli A, Villanacci V, Chiappa S, et al. Dietary
protein-induced proctocolitis in childhood. Am J
Gastroenterol 2008;103:2605–12.
64. Taylor SL, Stratton JE, Nordlee JA. Histamine poisoning
(scombroid fish poisoning): an allergy-like
intoxication. J Toxicol Clin Toxicol 1989;27:225–40.
65. Morrow JD, Margolies GR, Rowland J, et al. Evidence
that histamine is the causative toxin of scombroid-fish
poisoning. N Engl J Med 1991;324:716–20.
66. Kelso JM, Lin FL. Skin testing for scombroid poisoning.
Ann Allergy Asthma Immunol 2009;103:447.
67. Keller KM, Burgin-Wolff A, Lippold R, et al. The
diagnostic significance of IgG cow’s milk protein
antibodies re-evaluated. Eur J Pediatr 1996;155:
331–7.

CHAPTER

5 

Atopic Dermatitis and Food Allergy
Tamara T. Perry, Debra D. Becton and Stacie M. Jones

KEY CONCEPTS
Atopic dermatitis (AD) is a chronic skin disorder with
hallmark features of tissue inflammation and epidermal
barrier dysfunction.
 Food allergy is an important trigger for AD.


Introduction
Atopic dermatitis (AD) is a complex, chronic inflammatory skin disorder that is often associated with
food allergy. It is a multifactorial disease linked to
a complex interaction between skin barrier function, genetics and environmental factors, including
commonly encountered triggers such as allergens,
microbes and irritants. As early as the 1890s, the
term neurodermatitis was used to describe a chronic,
pruritic skin condition seen in patients felt to have
a nervous disorder. By the early 1900s, others had
noted the occurrence of a similar disorder with
asthma and hay fever, and used the term atopy to
further describe the combination of these diseases.
The term atopic dermatitis was then coined by Wise
and Sulzberger1 in 1933 to more fully describe this
skin disorder. Since its earliest description, AD has
had as its primary feature intense pruritus triggered
by a variety of stimuli. In this chapter, we explore
the link between allergic sensitization to specific
foods and the condition of AD.
The term ‘atopic march’ has been coined to
describe the natural history and sequential
© 2012, Elsevier Inc

35–40% of infants and young children with moderate to
severe AD will have food allergy.
 Food allergy is more likely to be a complicating factor if
AD is severe or presents in the first year of life.


progression of atopic disorders.2 Atopic dermatitis
is often considered the first manifestation of the
atopic march, since clinical symptoms of AD often
precede the development of other atopic disorders
such as allergic rhinitis and asthma. Approximately
60% of children affected by AD will develop symptoms in the first year of life and 85% will do so by
age 5. Moreover, as many as 50–80% of children
with AD will develop allergic respiratory disease
(e.g. asthma and allergic rhinoconjunctivitis) later
in life. Because of these strong associations, investigators have explored the role of various allergens,
including food allergens, as triggers in the pathogenesis of AD.
Food allergy has been strongly correlated with the
development and persistence of AD, especially
during infancy and early childhood.3,4 Also, the
skin is the site that is most often involved in food
hypersensitivity reactions.5 In sensitized individuals, food allergen exposure often results in urticaria,
itching, and eczematous skin flares. Sensitization
and subsequent allergic reactions can occur to any
food, but those most commonly associated with
AD are milk, egg, soy and peanut. Although

Food Allergy

allergies to some foods are typically outgrown,
others such as peanut or shellfish allergy, may
persist and continue to aggravate AD symptoms
into late adolescence and adulthood.3,6–8

Epidemiology
The prevalence of food allergy in patients with AD
varies with the age of the patient and the severity
of AD. In a study of 2184 Australian infants, investigators found an association between high levels
of food-specific IgE and earlier age of onset of AD
and increased disease severity.9 This group found
that AD patients who developed severe disease
within the first 3 months of life most commonly
had specific IgE to cows’ milk, egg and peanut, and
were at highest risk for developing food allergy. In
another study, investigators noted that in some
infants sensitization precedes and predicts the
development of AD, whereas in others AD precedes
and predicts the development of sensitization. In a
meta-analysis on the prevalence of food allergy,
Rona and colleagues10 reported that up to 37% of
children with moderate to severe AD had evidence
of IgE-mediated allergies to foods. Similarly, in a
study of children with AD, Burks et al.5 diagnosed
food allergy in approximately 35% of 165 patients
with AD referred to both university allergy and dermatology clinics. Later, Burks and colleagues5 published findings that 82% of 138 peanut-allergic
children seen in an allergy referral clinic had AD.
Eigenmann et al.11 studied 63 unselected children
(median age 2.8 years) with moderate to severe AD
who were referred to a university dermatologist and
reported that 37% of these patients were diagnosed
with food allergy after an evaluation that included
oral food challenges. Similarly, in a study of more
than 250 French children with an established diagnosis of AD, investigators noted that increased
severity of AD in the younger patients was correlated with the presence of food allergy.12

CLINICAL CASE
AN presented at 9 months of life with symptoms of
pruritus, inconsolable crying and sleep disturbance
attributed to severe, uncontrolled AD despite topical
corticosteroid therapy and emollients. A diagnostic
evaluation for food allergy was initiated because of AN’s
history of urticarial rash with exposure to multiple foods
and history of poorly controlled AD. Testing revealed
specific sensitivities to multiple foods, including milk
(0.56 kU/L), egg (1.14 kU/L), soy (2.15 kU/L), peanut
62

(20.0 kU/L) and rice (6.38 kU/L). Strict dietary elimination of
these foods, along with topical corticosteroids, emollients
and antimicrobials for secondary skin infection, led to a
dramatic improvement in both skin symptoms and
behavior. At 2 years of age, AN’s skin symptoms remain
controlled on dietary restriction and topical therapies
(Fig. 5.1).

To date, studies in adult patients have been limited,
and none accurately predict the prevalence or role
of foods in AD. In one systematic review of randomized controlled trials to assess the effects of
dietary elimination in a mixed group of both children and adults with established AD, investigators
concluded that elimination diets were not beneficial in unselected cases.13 However, there was significant clinical improvement when egg elimination
was prescribed for patients with suspected egg
allergy. Clearly more work is needed in older adolescent and adult populations to better understand
the role of food allergy in AD in these age groups.

Pathogenesis
There are two distinguishing features important to
the pathogenesis of AD, cutaneous inflammation
and defective epidermal barrier function. Additionally, genetics may play an important role in the
pathogenesis of both AD and food allergy.14 The
inflammatory response noted in AD involves both
adaptive and innate immunity. The hallmark allergic inflammatory response associated with AD
results from antigen-induced changes that include
both T-helper cell type 1 (Th1) and type 2 (Th2)
profiles of inflammation. Allergen-induced IgEmediated mast cell activation results in hypersensitivity reactions characterized by tissue infiltration of
eosinophils, monocytes and lymphocytes. In acute
AD the patterns of cytokine and chemokine expression found in infiltrating lymphocytes are predominantly those of the Th2 type (e.g. IL-4, IL-5 and
IL-13).15,16 Epidermal, myeloid-derived dendritic
cells express high-affinity IgE receptors (FcεRI) that
bind IgE and which are noted in biopsy tissue from
inflamed AD skin. These cells take up and present
allergens to Th1, Th2 and T-regulatory cells, all of
which are important in AD.17 In addition, IgEbearing Langerhans’ cells are highly efficient at presenting allergens to T cells, thereby activating a
combined Th1/Th2 profile in chronic AD lesions.
These findings support a combination of specific
IgE antibody, Th1 and Th2 cytokines/chemokines

Atopic Dermatitis and Food Allergy

A

C

B

D

5

Figure 5.1  AN presented at 9 months of age with severe AD (A, B), behavior problems and sleep disturbance due to intense
pruritus. One year later, (C,D) the same patient presented with dramatically improved skin and behavior after elimination of relevant
food allergens, topical therapies, antihistamine therapy and a course of antimicrobials for a secondary S. aureus skin infection.

in the pathogenesis of AD. The role of food-specific
T cells in the pathophysiology of AD has been considered for decades. The atopic patch test (APT) has
been used to further evaluate specific allergens and
subsequent T-cell activation in affected skin. In
some patients who may have a delayed response to
foods, investigators hypothesize that the reactions
may occur via high-affinity IgE receptors expressed
on Langerhans’ and dendritic cells, leading to
allergen-specific T-cell responses capable of promoting both IgE production and delayed-type
hypersensitivity reactions. The APT results demonstrate allergen-specific T-cell infiltration as evidence
supporting T-cell involvement in the pathogenesis
of AD.18,19
Another key feature of AD is defective epidermal
barrier function. Important genetic mutations in
the epidermal structural protein filaggrin have been

identified as key defects resulting in epidermal
barrier dysfunction.20 These loss-of-function genetic
mutations result in decreased epidermal defense
mechanisms against allergens and microbes. Filaggrin gene mutations and resultant epidermal barrier
dysfunction have been linked to the development,
progression and severity of AD, as well as increased
susceptibility to skin infections. Epidermal barrier
dysfunction may result in increased penetration of
allergens through the skin, thereby making the skin
a potentially important route by which individuals
are sensitized to food and airborne allergens. Fox
and colleagues21 described a dose-dependent association between household peanut exposure and
increased risk for the development of peanut allergy.
Children with peanut allergy had significantly
higher environmental peanut exposure than nonallergic children and high-risk atopic children with
63

Food Allergy

egg allergy. This positive relationship between environmental exposure and disease development
remained significant after controlling for maternal
peanut consumption during pregnancy and lactation. Epidermal barrier dysfunction may also facilitate the ability of viral and bacterial microbes to
penetrate the skin, resulting in secondary infections
(e.g., chronic/recurrent methicillin-resistant Staphylococcus aureus (MRSA), molluscum contagiosum
and eczema herpeticum). These infections may
further facilitate or enhance the inflammatory
response and may serve to further weaken the
barrier function, thereby providing a feedback
mechanism for chronic disease.
Findings from several studies examining mutations in the filaggrin gene support the genetic link
between atopic dermatitis risk and increased propensity to develop other atopic disorders, such as
food allergies. In a meta-analysis of 24 studies on
filaggrin mutations and atopic dermatitis, as well as
17 studies on asthma, Rodriguez and colleagues22
concluded that filaggrin gene defects significantly
increased the risk of atopic dermatitis diagnosis
(odds ratio [OR] 3.12; 95% CI 2.57–3.79), as well
as more severe skin disease. Mutations were also
found to be significantly associated with the combination of asthma and AD, but not with asthma
in the absence of AD. In a German birth cohort of
871 children23 filaggrin gene mutations had a 100%
positive predictive value for the development of
asthma among children with atopic dermatitis and
early food sensitization. These findings suggest that
early genotyping for filaggrin gene defects may
identify specific populations at risk – perhaps those
with early food sensitization and AD – that might
benefit from early interventions aimed to reduce
progression of the atopic march.
Although filaggrin gene defects have been implicated as important risk factors for the development
and increased severity of AD, it should be noted
that the full implications of the filaggrin defects are
not completely understood.20 Not all patients with
filaggrin mutations have AD, and similarly not all
patients with AD have a known filaggrin gene
defect. Also, patients with filaggrin defects have
been reported to ‘outgrow’ symptoms of AD. These
observations support the notion that other factors,
such as genetics and environmental and dietary
exposures, are probably important in clinical manifestations of disease.
Other genetic mutations resulting in clinical
disease have provided further insight into the
64

relationship between AD and food allergy. Two
disorders provide particularly compelling information. IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) is a fatal disorder
characterized by autoimmune enteropathy, endocrinopathy, severe dermatitis, elevated serum IgE
and multiple food allergies. IPEX syndrome results
from a gene mutation that affects the FOXP3
protein.24 FOXP3 (known as the ‘master regulator’
for T cells) plays a central role in the generation of
regulatory T cells that are presumed to be important
for the balance between oral tolerance and food
allergy development. Similarly, mutations in the
serine protease inhibitor Karzal type 5 (SPINK5)
gene have been associated with Netherton syndrome, an autosomal recessive disorder characterized by an AD-like rash, associated Th2 skewing
and increased IgE levels.25 Japanese investigators
have recently found an association of SPINK5
mutations in children with AD and food allergy. In
another investigation, SPINK5 polymorphism was
significantly associated with increased disease
severity among Japanese children under 10 years
with AD and food allergy. Other investigators have
found variants in the gene for the proinflammatory
cytokine IL-13 in association with early sensitization to foods and total serum IgE levels among a
group of 453 children with AD in the Early Treatment of the Atopic Child (ETAC) cohort.26 Owing
to the long-standing historical associations of atopy
and AD within families, numerous investigators
have identified a population of over 80 genes that
have some association with AD. Those implicated
often relate to antigen presentation or cell- or
antibody-mediated responses, or those involving
cell signaling.14 Little is so far known about gene–
environment interactions in AD that may also have
important implications in association with food
allergy. These genetic studies provide evidence that
food allergy and AD are likely to be genetically
linked with varying degrees of disease expression
within patient populations. Additional genetic
studies, in larger and more diverse populations, are
in progress to further identify the genetic link
between food allergy and AD and will probably
provide additional genes of interest.

Clinical features
A variety of allergic and non-allergic triggers are
known to aggravate and complicate the condition

Atopic Dermatitis and Food Allergy

Table 5.1  Important triggers of atopic dermatitis

Food allergens
Milk*

Tree nuts

Eggs*

Fish

Peanuts*

Shellfish

Soy

Wheat

Aeroallergens
Dust mites

Animal dander

Pollen

Cockroach

5

have now shown that AD may be delayed or prevented by exclusive breastfeeding, the introduction
of hydrolyzed infant formulas or by eliminating
highly allergenic foods such as milk and eggs from
the diet.27 Also, recent investigations have reported
on the relevance of cutaneous exposure to allergens
in the development of food allergy.21,28

Clinical evidence supporting
the relationship between AD
and food allergy

Mold

Microbes
Bacteria

Fungi/yeasts

Staphylococcus aureus

Pityrosporum ovale

Streptococcus species

Pityrosporum obiculare
Trichophytan species
Candida albicans
Malazassia furfur

Other factors
Irritants: soaps, detergents, fragrances or fabrics
Climate or temperature changes
Psychosocial: anxiety or stress
*Most common foods in infants and young children with AD.

of AD (Table 5.1). The role of food allergy in the
development or progression of AD has been a topic
of debate among clinicians for years, with multiple
clinical studies attempting to address the issue.
Whether food allergy can aggravate AD is still controversial, owing largely to the fact that signs and
symptoms of both food allergy and AD are pleomorphic, and because well-designed clinical trials
of food allergen elimination in patients with AD
have rarely been performed. In clinical studies,
investigators have shown that elimination of the
relevant food allergen can lead to improvement in
skin symptoms (Fig. 5.1) and that repeat challenges
can lead to recurrence of symptoms. Other studies
focusing on the immunologic mechanisms have
provided evidence supporting the role for foodspecific IgE antibodies and T-cell involvement in
the disease manifestations of AD. Additionally,
several longitudinal studies in high-risk infants

A number of studies have addressed the therapeutic
effect of dietary elimination in the treatment of AD.
Many of these trials, however, have limitations due
to the failure to control for confounding factors
such as placebo effect, observer bias, environmental
factors and other triggers. In a study of children
with AD between the ages of 2 and 8 years, Atherton
et al.29 showed marked improvement in two-thirds
of subjects during a double-blind crossover trial of
milk and egg exclusion. The study, however, was
complicated by high dropout and exclusion rates as
well as a lack of control of environmental factors
and other triggers of AD. Another study by Juto
et al.30 reported that approximately one-third of AD
patients had resolution of their rash, and that half
improved on a highly restricted diet. The cumulative results of these studies support the role for
foods as triggers in the exacerbation of AD in children. In an early prospective study, Sampson and
Scanlon3 studied 34 children with AD, 17 of whom
had food allergy diagnosed by double-blind,
placebo-controlled food challenges (DBPCFCs).
During 1–4-year follow-up periods, food-allergic
patients with appropriate dietary restriction demonstrated significant improvement in their AD
compared with the control groups (those without
food allergy, or food-allergic patients who did not
adhere to dietary restrictions). Lever and colleagues31 performed a randomized controlled trial
of egg elimination in young children with AD
and a positive specific IgE test to egg. Fifty-five children were identified by oral food challenge to be
egg allergic. There was a significant decrease in the
skin area affected and in symptom scores in the
children adhering to an egg-avoidance diet compared to the control subjects on no dietary avoidance (percent involvement 21.9–18.9%; symptom
score 36.7–33.5).
65

Food Allergy

CLINICAL CASE
KF was a 14-month-old with a history of recalcitrant AD.
Symptoms of eczematous rash and severe pruritus were
not relieved with emollient therapy and twice daily
medium-potency topical corticosteroid ointment. Food
allergy was suspected and testing led to the diagnosis of
egg allergy, with egg-specific IgE of 7.75 kU/L (nl <0.35).
Two months after strict egg elimination, KF’s AD was well
controlled with emollient therapy alone.

Oral food challenges have also been used to demonstrate that food allergens can induce symptoms of
rash and pruritus in children with food allergyrelated AD. Double-blind placebo-controlled food
challenges (DBPCFC) are considered the gold
standard for the diagnosis of food allergy, especially
in the setting of AD. Several investigative groups
have published reports using DBPCFCs to identify
causal food proteins that serve as triggers for AD.
Multiple studies using oral food challenges have
demonstrated a predominance of cutaneous symptoms as manifestation of a positive food challenge.7,21,32 These studies have shown that cutaneous
reactions occurred in 75% of the positive challenges,
generally consisting of pruritic, morbilliform or
macular eruptions in the predilection sites for AD.
Isolated skin symptoms were typically seen in only
30% of the reactions, and gastrointestinal (50%)
and respiratory (45%) reactions also occurred.
Investigators have also confirmed that a limited
number of foods cause clinical symptoms in younger
patients with AD (Table 5.2). Milk, eggs and peanuts
generally cause more than 75% of the IgE-mediated

Table 5.2  Relevant food allergies in atopic dermatitis
according to age

Infants

Children

Older children/adults

Milk

Milk

Peanuts

Eggs

Eggs

Tree nuts

Peanuts

Peanuts

Fish

Soy

Soy

Shellfish

Wheat
Tree nuts
Fish
Shellfish
From Sicherer SH, Sampson HA. Food hypersensitivity and atopic
dermatitis: pathophysiology, epidemiology, diagnosis, and
management. J Allergy Clin Immunol 1999; 104: S114–S122.

66

reactions. If soy, wheat, fish and tree nuts are added
to this list, more than 98% of the foods that cause
clinical symptoms will be identified.4,5,33

Immunologic evidence supporting
the relationship between AD and
food allergy
Several studies investigating the immunologic
mechanisms of disease have provided support for
the role for food-specific IgE antibodies in the
pathogenesis of AD. Many patients with AD have
elevated concentrations of total IgE and foodspecific IgE antibodies. More than 50 years ago,
Wilson and Walzer34 demonstrated that the ingestion of foods would allow antigens to penetrate the
gastrointestinal barrier and then be transported in
the circulation to IgE-bearing mast cells in the skin.
More recent investigations have shown that in children with food-specific IgE antibodies undergoing
oral food challenges, positive challenges are accompanied by increases in plasma histamine concentration, elaboration of eosinophil products, and
activation of plasma eosinophils.35–37 Children with
AD who were chronically ingesting foods to which
they were allergic have been found to have increased
spontaneous basophil histamine release (SBHR)
from peripheral blood basophils in vitro compared
with children without food allergy or normal subjects.38 After starting the appropriate elimination
diet, food-allergic children experienced significant
clearing of their skin and a significant fall in their
SBHR. Other studies have shown that peripheral
blood mononuclear cells from food-allergic patients
with high SBHR elaborate specific cytokines termed
histamine-releasing factors (HRFs) which activate
basophils from food-sensitive – but not foodinsensitive – patients. Food allergen-specific T cells
have been cloned from normal skin and active skin
lesions in patients with AD. In addition, cutaneous
lymphocyte-associated antigen (CLA) is a homing
molecule that interacts with E-selectin and directs
T cells to the skin. One study compared patients
with milk-induced AD to control subjects with
milk-induced gastrointestinal reactions without AD
and with non-atopic controls. Casein-reactive T
cells from children with milk-induced AD had a
significantly higher expression of CLA than did
Candida albicans-reactive T cells from the same
patients and either casein- or C. albicans-reactive T
cells from the control groups.39

Atopic Dermatitis and Food Allergy

Environmental and dietary exposures
important in the development of AD
and food allergy
An alternate and emerging paradigm that opposes
the traditional model of food allergen sensitization
via the ingestion route has been championed by
several investigators. This suggests that sensitization
to food allergens can occur via cutaneous exposure
to antigen owing to poor barrier function in AD
skin. Lack and colleagues28 have confirmed peanut
allergy in preschool children with AD and increased
exposure to peanut-based skin oils. These observations, along with mouse studies demonstrating that
epidermal application of ovalbumin results in the
development of eczematous lesions and ovalbuminspecific IgE production, have led Lack to hypothesize that environmental exposure to allergens
through the skin of infants’ with AD is responsible
for allergen sensitivity and allergic disease. As previously noted, this group found a dose-dependent
association between peanut exposure in the home
and an increased risk for the development of peanut
allergy.21

CLINICAL CASE
TD was a 15-month-old with a history of mild AD
presenting for evaluation of peanut allergy. TD had no
known history of peanut ingestion, yet the parents
reported two separate incidents of erythema and hives on
her cheek within 5 minutes of receiving a kiss from her
mother who had recently ingested peanuts. Peanutspecific IgE was 12.5 kU/L. Detailed dietary history
confirmed that there was no history of peanut ingestion
by TD; however, family members consumed peanut butter
on a regular basis.

In addition to these environmental investigations,
longitudinal studies have been conducted in general
population birth cohorts and cohorts of high-risk
infants to determine the role of breastfeeding,
maternal diet restriction during pregnancy and lactation, the use of hydrolyzed formulas and delayed
food introduction on the development of AD and
other atopic diseases.27 To date, maternal dietary
restriction of allergenic foods during pregnancy and
lactation has not been shown to significantly affect
the development of atopic disease in infants. A
recent meta-analysis determined that exclusive
breastfeeding during the first 3 months of life is
associated with lower incidence rates of AD during
childhood in children with a family history of

5

atopy.40 In two series, infants from atopic families
whose mothers excluded eggs, milk and fish from
their diets during lactation (prophylaxis group) had
significantly less AD and food allergy at 18 months
than those whose mothers’ diets were unrestricted.
Follow-up at 4 years showed that the prophylaxis
group had less AD, but there was no difference in
food allergy or respiratory allergy.41,42
In a comprehensive, prospective randomized
allergy prevention trial, Zeiger and colleagues43,44
compared the benefits of maternal and infant food
allergen avoidance on the prevention of allergic
disease in infants at high risk for allergic disease
during a 7-year longitudinal study. Breastfeeding
was encouraged in both prophylaxis (dietary allergen restriction) and control (usual feeding without
dietary restriction) groups. Compared to controls,
the prevalence of AD and food allergy in the prophylaxis group was reduced in the first 2 years;
however, the period prevalence of AD was not significant beyond 2 years. In the German Infant
Nutritional Intervention Study (GINI),45 2252
healthy term infants were randomized to receive
one of four blinded formulas during the first 4
months of life when breastfeeding was insufficient:
partially (PHW) or extensively hydrolyzed whey
(EHW), extensively hydrolyzed casein (EHC) or
cows’ milk (CM). The 6-year follow-up study
showed a long-term preventive effect of hydrolyzed
infant formulas for AD until age 6 years, with the
relative risk of a physician diagnosis of AD compared with CM of 0.79 (95% CI, 0.64–0.97) for
PHW; 0.92 (95% CI, 0.76–1.11) for EHW; and 0.71
(95% CI, 0.58–0.88) for EHC. Similar findings
were noted in a high-risk birth cohort of 120 infants
from the Isle of Wight followed for 8 years. Infants
in the intervention group (low-allergen diet, hypoallergenic formula and dust mite avoidance) were
noted to have less asthma, AD, allergic rhinitis and
atopy than those in the control (routine care and
feeding) group.
A recent meta-analysis of intervention studies
using partially hydrolyzed whey (PHW) formula
versus standard cows’ milk formula feedings in
infants at high-risk for atopy showed an advantage
of PHW formula in reducing the risk of AD development during the first 12 months of life. This
analysis indicated a 55% decreased risk of AD
through 6–12 months among infants who were fed
PHW formula.46 Conversely, several studies in prospective birth cohorts have shown no benefit in
delayed dietary introduction of solid foods past 4
67

Food Allergy

months of life on the development of AD, and even
note that delayed introduction may be associated
with a higher risk of AD.47
These studies have led to new recommendations
for early nutritional interventions in infants at high
risk (defined as one parent or sibling with atopic
disease) by the American Academy of Pediatrics
(2008),27 including 1) breastfeeding for the first
4–6 months of life; 2) the use of an extensively
hydrolyzed casein (or a partially hydrolyzed whey
formula) instead of cows’ milk or soy formula
when breastfeeding is inadequate during the first
4–6 months of life; and 3) delaying the introduction of solid foods until 4–6 months of age, but not
beyond. These recommendations are different from
those published by the AAP in 2000, which recommended the delayed introduction of highly allergenic foods in high-risk infants (e.g. peanuts until
age 3 years).48 Currently, there are no general guidelines to address the delayed introduction of allergenic foods for high-risk infants and children who
have early manifestations of atopic disease such as
food allergy or AD. Recommendations for elimination diets or delayed food introductions for highrisk infants should be determined on an individual
basis after consultation and testing by a medical
professional trained in the diagnosis and management of food allergies.
Ongoing longitudinal studies may shed further
light on the role of food allergy and AD. The NIHfunded Consortium of Food Allergy Research
(CoFAR; https: //web.emmes.com/study/cofar/) has
recently published the baseline characteristics of
512 infants enrolled in a longitudinal observational
study of food allergen sensitization and clinical
manifestations of food allergy, including the presence of AD.49 Enrollment criteria for the study
included either a positive SPT to egg or milk antigen
and either a convincing history of egg or milk allergy
or evidence of moderate to severe AD. Allergen sensitization was noted to milk in 78%, egg in 89% and
peanut in 69% of subjects at the time of enrollment
(ages 3–15 months). Of the subjects, 204 were
enrolled based on AD criteria and had never had an
acute food-allergic reaction. Lack and colleagues50
have also suggested a link between food- specific IgE
sensitization and cutaneous exposure to antigen
through inflamed AD skin lesions and the potential
role of early introduction of dietary allergens in
reducing atopic manifestations. Similar to findings
from the CoFAR group, early results from the
LEAP study (Learning Early About Peanut Allergy;
68

www.leapstudy.co.uk) indicate a similar high prevalence of food allergen sensitization associated with
AD in early infancy. The LEAP study has enrolled
approximately 480 infants with AD and/or egg
allergy and will follow them for 5 years in two treatment groups, one avoiding peanuts and the other
eating peanuts. These long-term follow-up studies
hold promise to provide additional information on
the role of food allergy, the timing of food allergen
exposure, and environmental and genetic factors
that surround the complex issue of food allergy
and AD.

Diagnosis
The diagnosis of food allergy in AD may be straightforward in cases with associated signs and symptoms of distinct anaphylaxis. The diagnosis of food
allergy in AD, however, is frequently complicated
by several factors: the immediate response to the
ingestion of causal foods is downregulated with
repetitive ingestion, making obvious ‘cause-andeffect’ relations difficult to establish; other environmental trigger factors (e.g. inhalant allergens,
irritants, microbes) may play a role in the course of
disease, often obscuring the effect of dietary
changes;51,52 and specific IgE to multiple allergens is
commonly found to many foods, many of which
are not associated with clinical symptoms, making
a diagnosis based solely on laboratory testing difficult.53 A combination of history, laboratory assessment and dietary manipulation with oral food
challenge is often needed to confirm or refute the
diagnosis of food allergy in association with AD
(Fig. 5.2).

CLINICAL CASE
CJ was a 4-year-old girl with multiple atopic disorders
including severe AD, asthma and various food allergies.
Her reactions to foods included both immediate IgEmediated symptoms after ingestion (urticaria and lower
respiratory symptoms) and multiple foods that resulted in
AD flare 24–48 hours after ingestion. Her course was
complicated by poor nutritional status owing to multiple
food restrictions, and IgE testing was positive to all foods,
with a total serum IgE 2002 kU/L (0.3–133 kU/L). After a
detailed dietary history and oral challenges to foods with a
low index of suspicion for reaction, CJ was able to
introduce several nutritionally relevant foods to her diet.
One year later, her nutritional status and weight gain were
appropriate.

Atopic Dermatitis and Food Allergy

Topical anti-inflammatory agents
Emollients
Antipruritics
Irritant and environmental control measures
Antimicrobial therapy (as indicated)

History not suggestive of
food allergy. Symptoms
controlled with above regimen

Food allergy suspected

Detailed dietary history
to elicit suspect foods

Specific IgE testing
(SPT and/or Food-specific IgE)
Dietary Elimination(s)
Oral food challenge(s)

Continue to monitor for disease
control and secondary skin infection.
Adjust topical therapies, medications,
and other control measures
as clinically indicated

Figure 5.2  Treatment algorithm for atopic dermatitis (AD). The
majority of patients with AD are adequately controlled with a
tailored combination of topical anti-inflammatory medications,
anti-pruritic therapy, emollients, and environmental control
measures. Selected patients may need antimicrobial treatment
for secondary skin infections. Patients with moderate–severe or
recalcitrant AD require further investigation to determine the
presence of food allergies. Specific IgE testing, dietary
elimination and oral food challenges can aid in the accurate
diagnosis of clinically relevant food triggers. All patients should
be monitored periodically to assess control of symptoms, and
medication and dietary modifications made as clinically
indicated. (SPT, skin prick testing.)

A careful medical history is essential in the diagnostic evaluation. For breastfed infants a maternal
dietary history is essential owing to the passage of
food proteins in breast milk to the infant.27 Selected
foods should then be evaluated by testing for
specific IgE (e.g. skin prick test [SPT], food-specific
IgE immunoassay). A small number of foods
account for more than 90% of reactions, and the
most common food allergens are listed in Table
5.2.33,54,55 Food additives have been documented to
cause flaring of AD but with a much lower prevalence.56,57 Emerging evidence suggests that chemical

5

contaminants in foods (such as oleoresins in fruits,
vegetables and spices) or metals or fragrances in
foods (such as Balsam of Peru in chocolate or citrus
fruits) may cause forms of local or systemic allergic
contact dermatitis that may also resemble flares of
AD and require food elimination for resolution of
symptoms.
As noted in Chapter 13, the diagnosis of food
allergy is enhanced by the use of IgE testing to specific foods. In particular, skin prick tests and IgE
immunoassays have proved useful, but although
helpful, these tests can often be misleading in the
setting of concomitant persistent AD. Patients with
AD will often have positive SPTs and/or foodspecific IgE tests to several members of a botanical
family (e.g. cereal grains and grass pollen) or animal
species (e.g. milk and beef). These commonly indicate immunologic cross-reactivity but not relevant
intrabotanical or intraspecies cross-reactivity of
clinical importance. Therefore, the practice of avoiding all foods within a botanical family when one
member is suspected of provoking allergic symptoms is generally unwarranted. Rather, the judicious
use of specific IgE testing, coupled with clinical
history, response to dietary manipulation and possibly oral food challenge, may be needed to make
an appropriate diagnosis of food allergy in a patient
with AD.58
After laboratory studies, the best initial treatment
is elimination of the suspected food(s) from the
diet, followed by an oral food challenge if indicated. No further testing or food challenges are necessary in cases of severe, acute clinical reactions or
anaphylactic reactions associated with food ingestion or exposure (e.g. inhalation or topical), or if
dramatic improvement in skin disease occurs with
dietary elimination. Because symptoms are chronic
in AD and multiple foods may be implicated by
specific IgE testing, it is often necessary to perform
diagnostic oral food challenges.
Oral food challenges can be invaluable in the
appropriate diagnosis and management of patients
with AD and possible food allergy.59 For patients
with persistent AD despite optimal topical therapies, oral challenges to major food allergens should
be considered when diagnostic testing (food-specific
IgE levels and/or SPT) do not correlate with a history
of clinical reaction. Oral challenges are also necessary to evaluate the resolution (or the development
of natural tolerance) of the specific food allergy and
can be performed safely. However, oral challenges
are contraindicated when there is a clear recent
69

Food Allergy

history of food-induced anaphylaxis. Additionally,
patients should be instructed not to perform food
challenges of suspect foods at home (or away from
medical intervention) because of the potential risk
of severe or life-threatening allergic reactions.60,61

Management
Despite the fact that investigators have published
case reports since the early 1900s of patients whose
AD improved after avoiding specific foods, only
more recently have larger clinical studies been published to validate the role of food allergy diagnosis
and management in the overall management of
AD. Despite persistent controversy about the role of
food allergy in the pathogenesis of AD, there is
now significant laboratory and clinical evidence
that would suggest the debate is no longer valid.
The elimination of food proteins can often be
difficult, and incomplete elimination of the offending food can lead to confusion and inconclusive
results during an open trial of dietary elimination.
For example, in a milk-free diet, patients must be
instructed not only to avoid all milk products but
also to read all food labels to identify ‘hidden’
sources of cows’ milk protein. For example, ingredients such as natural flavoring, caramel flavoring,
brown sugar flavoring or margarine may contain
milk. Another important issue regarding food
restrictions is related to the economic and social
impact of dietary elimination.62,63 Patients avoiding
multiple foods may find it difficult to adhere to a
diet that eliminates major food groups owing to the
cost of allergen-free alternatives, inconvenience, the
complexity of dietary needs and taste preferences.
Adequate understanding of clinical testing and
interpretation of results must be paired with appropriate dietary restrictions – typically only a few
foods – to avoid unnecessary dietary restrictions
and potential complications.
Care must be taken to ensure that patients on
elimination diets have adequate resources, including dietary counseling and education, social support
and financial assistance, to best manage their
disease. The role of dietary counseling through a
registered dietitian cannot be over-emphasized. A
registered dietitian cannot only help with counseling regarding dietary avoidance of food allergens, label reading and cross-contact, but can help
the patient maintain a healthy, well-balanced diet
(e.g., calcium and vitamin D supplementation
70

during a milk-avoidance diet). The triggers associated with disease pathogenesis and clinical symptoms in patients with AD are vast; however,
discerning the role of allergens as a trigger factor,
particularly food allergens, early in life is clearly
very important. A careful dietary history and appropriate diagnostic testing, coupled with a com­
prehensive treatment program, can be disease
modifying and life altering for patients with AD.
Other important aspects of the treatment program,
including intense moisturization and hydration,
topical anti-inflammatory agents such as corticosteroids or calcineurin inhibitors, irritant avoidance,
and antipruritic therapy, are essential to pair with
food allergy management for effective, comprehensive therapy (Fig. 5.2).

Natural history
The majority of children outgrow their allergies to
milk, eggs, wheat and soy,3,64 although recent
studies have shown that the rate of resolution of
some food allergens (e.g. egg and milk) may be
slower than previously described (Table 5.3). In
one study of the natural history of egg allergy in
children followed in a pediatric allergy practice,
investigators found that the age distribution of
resolution of allergy was 4% by age 4, 12% by age
6, 37% by age 10 and 68% by age 16.65 The eggspecific IgE level was predictive of allergy outcome
and can be used with skin testing to counsel patients
on prognosis. In another study, Perry et al.59 also

Table 5.3  Natural history of food allergy

Food

Median age
at diagnosis

Percent expected
to develop oral
tolerance

Milk

<12 mo

19–75% by age 4 years
(79% by age 16 years)

Egg

<12 mo

4–50% by age 4 years
(68% by age 16 years)

Soy

<12 mo

25% by age 4 years
(69% by age 10 years)

Peanut

14 mo

20% (8% recurrence
rate)

Tree Nuts

36 mo

<10%

Fish

>18 years

Not reported

Atopic Dermatitis and Food Allergy

showed that food-specific IgE levels are helpful in
determining the likelihood that a child has outgrown their food allergy. Patients allergic to peanuts,
tree nuts, fish and shellfish are much less likely to
lose their clinical reactivity.7,66 It does appear,
however, that approximately 20% of patients who
have a reaction to peanuts early in life may outgrow
their sensitivity.7 Only approximately 9% of patients
with tree nut allergy will outgrow their allergy.8
In one study approximately one-third of children
with AD and food allergy lost or outgrew their
clinical reactivity over 1–3 years with strict adherence to dietary elimination. Clinical reactivity is
lost over time more quickly than the loss of foodspecific IgE measured by SPT or serum food-specific
IgE testing; therefore, definitive diagnostic testing
(i.e. oral food challenges) may be necessary to
prevent unwarranted dietary restrictions. The combination of carefully following the history of accidental ingestions coupled with food-specific IgE
testing, and oral food challenges when indicated,
aids in determining when clinical tolerance is
achieved.

Conclusions
In summary, the role of food allergy in the potential
development, progression and maintenance of AD
is important to consider, especially in infants and
young children with refractory disease. As many as
35–40% of such children will have a food allergy
complicating their disease, which should be appropriately addressed using the clinical approaches
outlined in this chapter. Further investigations are
in progress to better refine diagnostic testing in children and adults with suspected food allergy and to
better define the role of elimination diets, timing
of introduction of allergenic foods, the role of
gene–environment interactions, and the relevance
of epidermal barrier function in the diagnosis and
management of food allergy and atopic dermatitis.
Most importantly, clinicians should maintain a
high index of suspicion for the potential role of
food allergy to best manage their patients with
atopic dermatitis.

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atopic dermatitis: evaluation of 113 patients. J Pediatr
1985;107(5):669–75.
55. Bock SA, Atkins FM. Patterns of food hypersensitivity
during sixteen years of double-blind, placebo-controlled
food challenges. J Pediatr 1990;117(4):561–7.
56. Fuglsang G, Madsen G, Halken S, et al. Adverse
reactions to food additives in children with atopic
symptoms. Allergy 1994;49(1):31–7.
57. Schwartz H. Food allergy: Adverse reactions to foods
and food additives. In: Asthmaandfood additives. 2nd
ed. Blackwell Science; 1997. In.

5

58. Lieberman JA, Sicherer SH. Diagnosis of Food Allergy:
Epicutaneous Skin Tests, In Vitro Tests, and Oral Food
Challenge. Curr Allergy Asthma Rep 2010;11(1):58–64.
59. Perry TT, Matsui EC, Kay Conover-Walker M, et al. The
relationship of allergen-specific IgE levels and oral food
challenge outcome. J Allergy Clin Immunol 2004;
114(1):144–9.
60. Perry TT, Matsui EC, Conover-Walker MK, et al. Risk of
oral food challenges. J Allergy Clin Immunol 2004;
114(5):1164–8.
61. David TJ. Hazards of challenge tests in atopic
dermatitis. Allergy 1989;44(Suppl. 9):101–7.
62. Mills EN, Mackie AR, Burney P, et al. The prevalence,
cost and basis of food allergy across Europe. Allergy
2007;62(7):717–22.
63. Sicherer SH, Noone SA, Munoz-Furlong A. The impact
of childhood food allergy on quality of life. Ann
Allergy Asthma Immunol 2001;87(6):461–4.
64. Bock SA. The natural history of food sensitivity.
J Allergy Clin Immunol 1982;69(2):173–7.
65. Savage JH, Matsui EC, Skripak JM, et al. The natural
history of egg allergy. J Allergy Clin Immunol
2007;120(6):1413–7.
66. Skolnick HS, Conover-Walker MK, Koerner CB, et al.
The natural history of peanut allergy. J Allergy Clin
Immunol 2001;107(2):367–74.

73

CHAPTER

6 

Food-induced Urticaria and
Angioedema
Julia Rodriguez and Jesús F. Crespo

KEY CONCEPTS
Urticaria/angioedema is the most common clinical
manifestation of IgE-mediated food allergy, either alone
or associated with other symptoms.
 IgE-mediated, food-induced urticaria/angioedema
usually occurs following ingestion of a food allergen(s),
but can also occur following topical contact, inhalation
or with food ingestion followed by exercise; in some
cases after a specific food or after any food.
 The most important effector cell in IgE-mediated
urticaria/angioedema is the mast cell in dermis and
mucosal tissues.


Introduction
Adverse reactions to food can be identified as
underlying causes in various urticarial diseases. IgEdependent allergic reactions to food are known to
play a role in acute urticaria, in some cases of
exercise-induced urticaria and in contact urticaria.
Food allergy can be defined as an adverse immune
response that occurs reproducibly on exposure to a
given food and is distinct from other adverse
responses to food, such as food intolerance, pharmacologic reactions and toxin-mediated reactions.
Allergic reactions after the ingestion of foods could
result in diverse manifestations as the result of
complex interactions among the causal food
protein, gut, immune system and target organs.
Although food initially contacts the gastrointestinal
mucosa, allergic manifestations frequently occur
© 2012, Elsevier Inc

Patients with food-induced IgE-mediated urticaria can
have a more severe reaction in the future.
 Once the diagnosis of clinical allergy to foods is
established, the only effective intervention therapy is
strict avoidance of the offending food. Cross-reactive
foods should be evaluated before advising the patient
that they can be safely consumed.


outside the gastrointestinal tract, with symptoms or
diseases affecting a variety of target sites alone
or in combination. Studies that used double-blind
placebo-controlled oral food challenges (DBPCFCs)
have also demonstrated the variety of organ systems
affected during food allergic reactions. In several
recent series of oral food challenges the skin was
commonly affected. There are several distinct manifestations of skin reactions caused by food allergy.
Most of these disorders are mediated by foodspecific IgE antibody that is bound to high-affinity
IgE receptors on mast cells. A typical skin reaction
after food ingestion is acute urticaria and
angioedema, which represents a clinical example
of a systemic symptom/disorder attributed to
food hypersensitivity. In addition, urticaria and
angioedema are the most common manifestations
of anaphylaxis, associated with other symptoms

Food Allergy

such as respiratory compromise, reduced blood
pressure or associated symptoms and/or persistent
gastrointestinal symptoms. Urticaria can also
appear on ingestion of a particular food or any
meal followed by exercise. The clinical syndrome
of food-dependent exercise-induced urticaria/
anaphylaxis (FDEIA) is typified by the onset of
urticaria/anaphylaxis during (or soon after) exercise
that was preceded by the ingestion of the causal
food allergen(s) within a specified period of time.1,2

CLINICAL CASE
An 18-year-old male presented to the emergency room; he
had been jogging for 30 minutes when he presented with
pruritus, disseminated urticaria, eyelid angioedema,
conjunctival erythema, nausea, vomiting, general malaise
and hypotension. He had eaten two apples 3 hours before
exercise. He had not taken any medication. Results for skin
prick testing for apple were positive (7 mm mean wheal).
Specific serum IgE (CAP FEIA) for apple also elicited a
positive result (1.95 kU/L). An open food challenge with
two apples without subsequent exercise was negative. An
exercise challenge test without prior apple consumption
was negative. Given the strong evidence from the clinical
history and the potential risks of anaphylaxis, no exercise
challenge test following apple consumption was carried
out in this patient. He was advised to allow 4 hours
between apple ingestion and exercise. He has not
reported any further episodes.

Acute urticaria and angioedema may be the result
of a local reaction elicited by direct contact with
food, and more rarely by the exposure to dust,
steam, vapors and aerosolized proteins generated
during cooking or boiling. These symptoms can
occur at home, in restaurants or in the occupational
setting.

CLINICAL CASE
A 38-year-old man reported multiple episodes since
childhood with pruritus, disseminated urticaria, eyelid and
lip swelling, facial erythema, difficulty swallowing,
wheezing and dyspnea minutes after entering seafood
restaurants and whenever shellfish was boiled at home. In
many of these episodes he required treatment in the
emergency room. He reported one episode of lip swelling,
oropharyngeal pruritus and dyspnea minutes after
ingestion of a single shrimp. He tolerated fish ingestion.
Skin prick testing and serum specific IgE (CAP-FEIA) elicited
positive results to shrimp (10 mm mean wheal and
25.7 kU/L, respectively). Since the last episode the patient
has not entered any seafood restaurants and no shellfish
has been kept at home. He has been instructed to avoid
shellfish ingestion and any food that could contain
shellfish, such as shellfish sauces and broth, to avoid areas
where shellfish are being boiled or cooked, to always carry
76

epinephrine when eating out of home and to selfadminister in case of inadvertent exposure/ingestion of
shellfish.

CLINICAL CASE
A 29-year-old woman had worked as a cook in a seafood
restaurant for the last 2 years. Two months before referral
she reported ocular erythema and pruritus, facial erythema
and hives, cough and dyspnea when shellfish species such
as shrimp, squid, clam or mussels were being boiled and
cooked. When she handled these foods, either raw or
cooked, she reported hand and arm pruritus and urticaria.
Minutes after the ingestion of two shrimps she reported
an episode of ocular erythema, oropharyngeal pruritus and
cough. Since then she has currently avoided shellfish
ingestion. Skin testing (prick by prick) carried out with raw
and boiled shellfish species brought in by the patient
elicited positive results (mean wheal raw/boiled) to shrimp
(12.5/10), squid (15/9), clam (8.5/7) and mussel (9/8.5).
Specific serum IgE (CAP FEIA) was also positive to shrimp
(29.1 kU/L), squid (3.29 kU/L), clam (15.3 kU/L) and mussel
(17.2 kU/L). The patient was diagnosed with allergy to
shellfish (crustaceae and mollusks: both cephalopods and
bivalves). She was strongly advised to change her job, or
at least try to avoid contact with and ingestion of shellfish
and any food that could contain shellfish, such as shellfish
sauces and broth, and being in areas where shellfish were
being cooked, to always carry epinephrine when eating
out of home, and to self-administer in case of inadvertent
exposure/ingestion of shellfish.

Immunological (allergic) contact urticaria is due to
immediate-type hypersensitivity; it is mediated primarily by histamine, and may be associated with
systemic and potentially life-threatening symptoms. Immunological contact urticaria to food may
occasionally affect those who handle food, and
may be associated with development of a protein
contact dermatitis.3
Chronic urticaria, defined as continuous wheals
and/or angioedema, presenting daily or almost
daily, that goes on for 6 weeks or more, is frequently
perceived by patients as food-induced; however,
virtually no reported food reactions in chronic
urticaria patients are confirmed by double-blind
placebo-controlled food challenge.4

Epidemiology
It is a general perception that acute urticaria and
angioedema are among the most common symptoms of food-allergic reactions, although the exact
prevalence of these reactions is unknown. A number
of clinical studies reviewed by Bindslev-Jensen and
Osterballe5 revealed that an average of 14% of

Food-induced Urticaria and Angioedema

patients with confirmed food allergy has been estimated to react with urticaria upon challenge. Some
insights on the prevalence of food-induced urticaria
could be provided by population-based studies,
including food challenge tests. A recent populationbased study in 6–9-year-old urban schoolchildren
living in Turkey estimated a prevalence of foodinduced urticaria of 0.6%, although the prevalence
of actual food allergy was 0.8%.6 As for the frequency of food-induced urticaria and angioedema
in the emergency department, a recent study analyzed food-allergic and anaphylactic events from 34
participating centers in the National Electronic
Injury Surveillance System (USA) in a 2-month
pilot program. There were 141 medical records,
including children and adults, that reported food
allergy-induced symptoms, the majority of which
were skin related. Urticaria and angioedema were
the most common: urticaria accounted for 38% if
cases; facial edema (face, tongue, eyes, oral cavity)
48%; general edema 4%; and laryngeal edema
(swelling of throat/uvula) 15%.7
Most cases of food-induced contact urticaria
occur in the occupational setting. In fact, bakers
and preparers of processed food were found to rank
among those most commonly affected by occupational contact urticaria in Finland.8 In the same
way, food was recognized as the second major
cause, after natural rubber latex, of occupational
contact urticaria in Australian patients with occupational skin disease.9
Exposure to food allergens through inhalation
can also cause food hypersensitivity reactions, with
symptoms that typically include respiratory manifestations such as rhinoconjunctivitis and asthma,
particularly in the occupational setting. In addition,
a limited number of investigations have reported
allergic reactions in the form of acute urticaria that
have occurred following exposure to fumes or
vapors from cooked foods, such as fish and legumes
(see Chapter 8).10,11
Urticaria/angioedema are the most frequent
symptoms seen in food-dependent exercise-induced
anaphylaxis (FDEIA). In a survey carried out in a
national hospital in Korea, this accounted for
13.2% of 138 anaphylactic reactions. Urticaria
(82%) and angioedema (70%) were the most
common symptoms observed and buckwheat was
the most frequent causal food.12 An epidemio­
logical study carried out in junior high-school students reported a frequency of 0.017% FDEIA. All
cases showed urticarial symptoms, which were also

6

documented in further challenges. The most frequent causative foods were crustaceans and wheat.13
In a 10-year follow-up study of patients with
exercise-induced anaphylaxis,14 one-third of the
cohort reported food triggered attacks. Urticaria,
pruritus and angioedema accounted for more than
80% of symptoms. Shellfish, tomatoes and wine
were the most frequently reported culprits.

Pathogenesis
The most important effector cell in urticaria/
angioedema is the mast cell in dermis and mucosal
tissues. This cell expresses high-affinity IgE receptors that bind to the constant region domain of IgE,
C3. Food allergens, whether ingested, through skin
contact or inhaled, react with IgE bound to the
patient’s tissue mast cells, and trigger the reaction
upon re-exposure to the antigen. This event elicits
mast cell degranulation and the subsequent release
of vasoactive mediators. Histamine, released by preformed granules, is the major mediator of urticaria
and angioedema. It elicits vasodilation and vascular
permeability, which is seen clinically as a wheal. An
axon reflex, caused by the release of the neuropeptide substance P from type C cutaneous fibers,
increases the extent of the reaction. Substance P
also further stimulates mast cells to increase their
histamine release. Other membrane-derived mediators such as prostaglandins and leukotrienes are
subsequently released, contributing respectively to
vasodilation and an increase in microvascular permeability, all of which allows fluid leakage into the
superficial tissues. In the case of FDEIA, exercise
may favor intestinal absorption of causative food
allergens or have some effect on the mast cell itself,
which can be detected in patients’ sera during the
food–exercise combined challenge and not with the
eliciting food or exercise separate challenge. Aspirin
is known as an aggravating factor in FDEIA patients:
it has been hypothesized that it may upregulate
intestinal absorption of antigen and/or increase
histamine release.15
Skin biopsies performed in 108 patients with
acute, chronic and physical urticaria showed dermal
edema and dilated lymphatic and vascular capil­
laries. Inflammatory infiltrates, with significantly
increased numbers of neutrophils and eosinophils,
were observed exclusively in the involved skin of all
patients. Mast cell numbers were higher in the
upper and lower dermis of lesional as well as the
77

Food Allergy

uninvolved skin of all patients.16 This fact, together
with increased levels of food-specific IgE bound to
skin mast cells, could provide an explanation for
the high frequency of urticaria/angioedema upon
food ingestion. Bloodborne food allergens absorbed
and processed in the gastrointestinal mucosa would
reach a sensitized, mast cell-populated skin ready
to react upon re-exposure.

Clinical features
After ingestion of the culprit food, urticaria and/or
angioedema may appear within minutes or up to
2 hours later. Urticarial lesions, preceded by or
appearing together with pruritus, are easily recognized. Wheals are intensely pruritic and involve any
area of the skin; they may appear in one location
and fade in another within minutes or hours.
Wheals vary in shape and size from millimeters to
a few centimeters. They may coalesce to form giant
lesions with raised borders. An individual wheal
does not persist over 24 hours. Pruritus is the hallmark, it is felt all over the skin, and worsens with
scratching. Pruritus in the palms and soles, usually
without wheals in those locations, may precede or
appear together with disseminated urticaria. This is
sometimes a warning signal of further severe symptoms. Angioedema is not usually pruritic: rather,
patients describe a burning or tingling sensation. It
may appear anywhere on the skin or on mucous
surfaces. Angioedema may be a life-threatening
symptom if airway obstruction occurs as a result of
laryngeal edema or tongue swelling.
The most frequent foods reported as causing urticaria on ingestion in children are egg, milk, peanuts
and tree nuts. In adults, fish, shellfish, tree nuts and
peanuts are reported as the most common. However,
the relative frequencies of different causal foods may
vary across geographical areas. In a study carried out
in 1537 German adults, 20% reported food allergy
symptoms. Skin reactions accounted for 8.7%. The
most frequently reported foods were fruits and
herbs/spices.17 A French study carried out in the
general population reported urticaria and angio­
edema as the most frequent food-elicited symptoms.
The most frequently reported foods were rosaceae
fruits, vegetables, milk, crustaceans, fruit crossreacting with latex, egg, tree nuts and peanut.18 In a
Mediterranean adult population from Turkey, vegetables, egg and fruits were the most frequent causal
foods eliciting urticaria and angioedema.19
78

Food-induced contact urticaria reactions may
erupt from minutes to 1 hour after exposure. A local
wheal and flare appears, usually pruritic, but tingling or burning may be reported by the patient.
The reaction can be exclusively local, but may
progress to a disseminated urticaria or present with
systemic symptoms, defined as contact urticaria
syndrome.20 Food handlers can also present with a
local IgE-mediated eczematous reaction known as
protein contact dermatitis, which can coexist with
contact urticaria; it can affect not only the hands
but the wrists and arms as well. The causal proteins
have been classified into four groups, the first three
of which include numerous foods, such as fruits,
vegetables, spices, plants and woods; animal proteins; grains; and enzymes. Virtually any job that
involves food handling can be at risk for foodinduced contact urticaria and/or protein contact
dermatitis: homemakers, cooks, food handlers,
mushroom growers, bakers, confectionery workers,
butchers, veterinarians etc.
In food-allergic patients urticaria and angioedema
may appear minutes after inhalation of cooking
fumes or aerosolized food particles, as an isolated
symptom, together with wheezing or progressing to
systemic anaphylaxis.10,11,21
Clinical symptoms of FDEIA usually have an
onset after around 10 minutes of exercise, and
within 2 hours after food ingestion. Generalized
urticaria, angioedema and erythema are the first
clinical manifestations and are usually followed by
respiratory and systemic symptoms, evolving into
systemic anaphylaxis.

Diagnosis
As with other adverse reactions to foods, the primary
tools available to diagnose food-induced urticaria/
angioedema include a detailed clinical history, diet
diaries as appropriate, physical examination, skin
testing, serum tests for food-specific IgE antibodies,
trial elimination diets, and oral food challenges.22
In the case of food ingestion, patients often identify
the offending food if symptoms begin within
minutes to 2 hours after consumption, especially if
they have experienced more than one episode with
these characteristics. It is important to note that if
symptoms are reported more than 3 hours after
ingestion and last for several days, a causal relationship with food is unlikely. Patients may report
symptoms appearing daily or on most days. In this

Food-induced Urticaria and Angioedema

case, they frequently try to associate urticaria with
a particular food(s); they should be questioned if
hives appear on each and every ingestion of that
food; if that is not the case, the causal relationship
may be excluded, unless the suspected food may or
may not contain a hidden allergen/contaminant,
e.g. mustard in some but not all ketchup brands,
lupine in some fortified pasta, scombroid fish poisoning, anisakis in seafood, etc. To search for a
consistent relationship between food and symptoms in these cases, a symptom diary including
frequency, timing, duration and severity of the
symptoms and foods ingested previously to the
episode may be kept by the patient. In the case of
symptoms after a meal composed of several foods,
all should be carefully listed and the patient questioned about further tolerance of any of these foods;
if that is the case, they should be excluded from the
suspicion list if they contain no possible hidden
allergens/contaminants, e.g. fresh fruits, meat, egg.
In all cases of suspected processed foods, patients
should be required to bring in the food label.
Auriculotemporal syndrome is a disease occasionally misdiagnosed as food allergy. Symptoms consist
of non-pruritic flushing and/or sweating in facial
areas while chewing or immediately after eating, for
example the cheeks or jaw supplied by the auriculotemporal nerve, which may be damaged by local
trauma, such as forceps delivery, virus or surgery.
Symptoms usually appear unilaterally, although
some bilateral cases have been documented.23
If symptoms are reported after contact of the food
with skin, patients usually identify the culprit
food(s). Timing of the reaction and circumstances
of onset should be recorded, especially in an occupational setting in which many different foods may
be handled. The relationship between possible
worsening at work and improvement in periods off
work should be investigated.
In the case of urticaria after a particular food
ingestion or any meal followed by exercise, information should be obtained on whether this food
or any food consumption is tolerated without
exercise, time between ingestion, exercise and onset
of symptoms, which usually occurs minutes after
beginning of exercise. Systemic manifestations
evolving to anaphylaxis should be recorded. The
concomitant administration of drugs prior to exercise, especially aspirin and other anti-inflammatory
drugs, should be asked about. FDEIA urticarial
lesions should be differentiated from cholinergic
urticaria, which presents with pinhead-sized wheals;

6

therefore, patients reporting FDEIA should be questioned about the characteristics of the skin lesions.
Moreover, the trigger in cholinergic urticaria is an
increase in core body temperature, sweating and
stress. Hot and spicy foods may increase sweating
and elicit cholinergic urticaria; therefore, a distinction should be made between this symptom in
patients with this condition and genuine food
allergy by means of complementary diagnostic
tools: skin testing and oral challenges if necessary.
In all cases patients should be questioned about
the characteristics of the lesions: site, duration of
individual lesions, whether they are pruritic or
painful, and if there are wheals lasting for more
than 24 hours. Associated angioedema should also
be questioned for. A useful procedure may be
to show patients photographs of urticaria and
angioedema and ask them if their hives and swelling look similar. A thorough physical examination
must be performed. Dermographism should be
explored by lightly scratching the skin. If positive,
wheals appear within 10 minutes locally. In the case
of recent urticarial lesions, lineal bruising caused by
scratching may be observed lasting for more than
24 hours. Any individual wheal lasting for more
than 24 hours, being painful or with ecchymosis or
petechiae, is concerning and should be investigated
by skin biopsy as it may be a vasculitic lesion. This
procedure also should be carried out in unusual
patterns of urticaria with suspicion of vasculitis
(fever, malaise and arthralgia). In this case the main
pathological findings would be leukocytoclasis –
that is, fragmentation of neutrophils with nuclear
dust in the infiltrate – red blood cell extravasation,
and fibrinoid degeneration of the endothelial cells.
This pattern is not found in genuine urticaria.
Skin prick testing (SPT) is the most useful procedure to detect sensitization (the presence of antibody) to the suspected ingested foods, but it is not
diagnostic of clinical reactivity. However, it is an
excellent tool to rule out food allergy as a cause of
urticaria/angioedema with 95% accuracy. A useful
variant is skin testing by the prick-by-prick procedure, which yields better results than commercial
extracts, particularly with fresh fruits and vegetables, as labile allergenic proteins in these foods may
be lost in extract processing. In vitro assays for specific serum IgE have similar sensitivities and specificities. The increasing size of the SPT or concentration
of food-specific IgE antibody by an in vitro assay
may be related to the likelihood of a clinical reaction for some foods;24 however, these values may
79

Food Allergy

vary depending on different age groups, different
foods and different in vivo and in vitro techniques.
Importantly, panels of food allergy in vivo and in
vitro tests should not be performed because many
clinically irrelevant positive results may be found in
cross-reactive foods.
As stated above, symptom diaries look for any
temporal relationship between food consumption
and urticaria, which often is ruled out in the case
of symptoms occurring more than 2 hours after
ingestion or lasting for several days.
Elimination diets might be the best way to help
the patients discard a food causal relationship for
their daily or persistent urticaria/angioedema, a
situation which they may desperately try to associate with ingestion of one or more particular foods.
Oral challenges administered openly, with the
food in its natural form and preparation reported
by the patient, are helpful in the case of several
reported foods. Challenges should also be carried
out in the case of single food consumption without
a clear-cut temporal relationship, and/or reported
reactions not evaluated by a physician when they
took place. If the food is tolerated, a causal relationship is ruled out. If the patient reports subjective
symptoms in the open challenge, a double-blind
placebo-controlled food challenge should be
carried out. In the case of a negative result a final
open challenge in an amount and preparation
similar to that which caused the original reaction
should be given.
The diagnosis of food contact urticaria can often
be confirmed by skin prick testing using commercial extracts or prick-by-prick testing with fresh
foods and the open patch test, evaluating the
appearance of local wheals 15–30 minutes after
application of the suspected eliciting agent. Other
topical application techniques, such as the chamber
prick test, the scratch test and the open test, in
which 0.1 mL of the test substance is spread over a
3 × 3-cm area of skin, can be used. Prick testing
theoretically has the lowest risk of anaphylaxis
because only minute amounts of allergen are introduced into the skin. The risk of other types of
topical food application techniques should be carefully weighed against the risk of anaphylaxis if the
patient reports extracutaneous symptoms with the
suspected food. Measurement of serum-specific IgE
can also be a useful diagnostic tool, especially in
these cases of severe urticaria contact syndrome.
In patients reporting occasional anaphylaxis after
food ingestion and exercise, challenge tests might
80

be indicated, especially if a particular food has not
been clearly identified. An oral challenge, without
subsequent exercise, should be performed. If the
result is positive FDEIA is excluded. In the case of
a negative result, an oral challenge followed by
exercise can be carried out to confirm the causative
food and the diagnosis.25 The procedure should be
performed under strict medical supervision, blood
pressure and pulse rate monitoring and an intravenous line. This test elicits a negative result in 30%
of patients, probably because of the different temperatures, humidity, type of exercise, amount of
food administered and other conditions of the
reported reaction.

Treatment
Once the diagnosis of clinical allergy to ingested
foods is established, the only effective therapy is
strict avoidance of the offending food and all others
that might contain it as a labeled component or as
a hidden allergen. After a specific food has been
identified and proved causal, recognition of crossreacting allergens in other foods is an important
issue. Since a very low rate of clinical cross-allergy
has been demonstrated among legumes, cereal
grains, egg–chicken and milk–cooked beef, it is not
appropriate to restrict entire families or groups that
include these foods. Avoidance of the entire food
group has been suggested to patients with allergy
to nut or shellfish families.26 In the case of fruit
elimination, diets limited to those proven to induce
allergic symptoms might overlook the risk of potential clinical cross-reactivity, when the patient has
not consumed other related fruits after the reaction.
Therefore, other foods of the same plant family or
antigenically related should be specifically tested by
oral challenges before advising the patient that
these fruits may be safely consumed.27
Both patients and caregivers should be informed
about the risks of inadvertent consumption, especially if the food is ubiquitous; they should be
instructed to correctly read and interpret labeling,
which could be misleading. For a patient allergic to
a particular food the term ‘may contain’ should
mean ‘contains’. In the case of foods consumed
boiled, such as legumes or crustaceans, broths used
to boil these foods should be avoided. Parents/
patients should be instructed on the risks of inadvertent ingestion of causal foods in schools, restaurants, markets, etc.

Food-induced Urticaria and Angioedema

Patients may experience a severe reaction after a
subsequent exposure to a food, even if previous
reactions were only cutaneous without any associated systemic symptoms. A subsequent exposure
may begin with urticaria/angioedema symptoms
and progress to a systemic reaction; therefore,
patients should be provided with self-injectable
epinephrine and instructions on its use in case of
the appearance of more severe symptoms beyond
urticaria/angioedema, such as dysphonia, difficulty
swallowing, nausea, vomiting, abdominal cramps,
dyspnea or fainting. Epinephrine should be administered early in the treatment of an anaphylactic
reaction. In addition, the patient should immediately seek appropriate medical care if he or she
develops a systemic reaction to a food.
Patients diagnosed with food-induced contact
urticaria should avoid foods and food products that
elicit symptoms. In the case of contact urticaria with
raw foods, such as fish or potato, patients may tolerate ingestion of cooked food. Cosmetics may
include food extracts in their formulations, which
could elicit reactions; therefore, cosmetic labels
should be carefully read. Patients with contact reactivity to latex should be investigated for tolerance
of latex-related foods, including skin testing, serumspecific IgE assessments and oral challenges if they
have not consumed those foods with tolerance after
the latex reaction. In the case of contact urticaria
syndrome patients may require self-injected epinephrine and subsequent medical care.
Patients with symptoms on inhalation of food
cooking fumes and/or raw fish odors should carefully avoid all risk situations at home, with cooking
or food handling and in fish markets. Depending
on the severity of the symptoms, they should be
instructed to carry self-injectable epinephrine.
In the case of FDEIA patients should avoid exercise, even milder than that which elicited symptoms, for 4–5 hours after eating the causal foods.
Patients with a history of a life-threatening reaction
should always carry self-injectable epinephrine.
In summary, urticaria/angioedema are recognized as one of the most common symptoms of
food-allergic reactions, although their exact pre­
valence is unknown. The most important effector
cell in IgE-mediated urticaria/angioedema is the
mast cell. Urticaria/angioedema can occur not only
by food ingestion but also by contact with foods;
in this case, allergic reactions can be local but may
also become severe and systemic. Urticaria induced
by inhalation of aerosolized food particles can

6

take place not only with fumes but also with raw
foods, at home, in food markets, in restaurants
and in occupational settings. Urticaria/angioedema
can also occur with food ingestion followed by
exercise, and be the first sign of a severe anaphylactic reaction. Diagnosis of food-induced urticaria/
angioedema must include a careful, thorough clinical history and the appropriate diagnostic tools,
depending on the different clinical features reported
by the patient. The hallmark of treatment is avoidance of the causal food. Cross-reactive foods should
be investigated before advising the patient that they
can be safely consumed.

References
1. Sicherer SH. Determinants of systemic manifestations
of food allergy. J Allergy Clin Immunol 2000;106(5
Suppl):S251–7.
2. Morita E, Kunie K, Matsuo H. Food-dependent
exercise-induced anaphylaxis. J Dermatol Sci
2007;47(2):109–17.
3. Killig C, Werfel T. Contact reactions to food. Curr
Allergy Asthma Rep 2008;8(3):209–14.
4. Zuberbier T, Balke M, Worm M, et al. Epidemiology
of urticaria: a representative cross-sectional
population survey. Clin Exp Dermatol 2010 Dec;
35(8):869–73.
5. Bindslev-Jensen C, Osterballe M. Other IgE- and non
IgE-mediated reactions of the skin. In: Metcalfe DD,
Sampson HA, Simon RA, editors. Food Allergy. Adverse
Reactions To Foods And Food Additives. 4th ed.
Blackwell Publishing Ltd; 2008. pp. 124–32.
6. Orhan F, Karakas T, Cakir M, et al. Prevalence
of immunoglobulin E-mediated food allergy in
6–9-year-old urban schoolchildren in the eastern
Black Sea region of Turkey. Clin Exp Allergy
2009;39:1027–35.
7. Ross MP, Ferguson M, Street D, et al. Analysis of
food-allergic and anaphylactic events in the National
Electronic Injury Surveillance System. J Allergy Clin
Immunol 2008;121:166–71.
8. Kanerva L, Toikkanen J, Jolanki R, et al. Statistical data
on occupational contact urticaria. Contact Dermatitis
1996;35:229–33.
9. Williams JD, Lee AY, Matheson MC, et al. Occupational
contact urticaria: Australian data. Br J Dermatol 2008;
159:125–31.
10. Crespo JF, Pascual C, Dominguez C, et al. Allergic
reactions associated with airborne fish particles in
IgE-mediated fish hypersensitive patients. Allergy
1995;50:257–61.
11. Martínez Alonso JC, Callejo Melgosa A, Fuentes
Gonzalo MJ, et al. Angioedema induced by inhalation
of vapours from cooked white bean in a child.
Allergol Immunopathol (Madr) 2005;33(4):
228–30.
81

Food Allergy
12. Yang MS, Lee SH, Kim TW, et al. Epidemiologic and
clinical features of anaphylaxis in Korea. Ann Allergy
Asthma Immunol 2008;100:31–6.
13. Aihara Y, Takahashi Y, Kotoyori T, et al. Frequency of
food-dependent, exercise-induced anaphylaxis in
Japanese junior-high-school students. J Allergy Clin
Immunol 2001;108:1035–9.
14. Shadick NA, Liang MH, Partridge AJ, et al. The natural
history of exercise-induced anaphylaxis: survey results
from a 10-year follow-up study. J Allergy Clin Immunol
1999;104:123–7.
15. Matsuo H, Morimoto K, Akaki T, et al. Exercise and
aspirin increase levels of circulating gliadin peptides in
patients with wheat-dependent exercise-induced
anaphylaxis. Clin Exp Allergy 2005;35:461–6.
16. Haas N, Toppe E, Henz BM. Microscopic morphology
of different types of urticaria. Arch Dermatol
1998;134:41–6.
17. Schäfer T, Böhler E, Ruhdorfer S, et al. Epidemiology of
food allergy/food intolerance in adults: associations
with other manifestations of atopy. Allergy
2001;56:1172–9.
18. Kanny G, Moneret-Vautrin DA, Flabbee J, et al.
Population study of food allergy in France. J Allergy
Clin Immunol 2001;108:133–40.
19. Gelincik A, Büyüköztürk S, Gül H, et al. Confirmed
prevalence of food allergy and non-allergic food

82

hypersensitivity in a Mediterranean population. Clin
Exp Allergy 2008;38(8):1333–41.
20. Bourrain JL. Occupational contact urticaria. Clin Rev
Allergy Immunol 2006 Feb;30(1):39–46.
21. Taylor AV, Swanson MC, Jones RT, et al. Detection
and quantitation of raw fish aeroallergens from an
open-air fish market. J Allergy Clin Immunol
1999;166–9.
22. Guidelines for the Diagnosis and Management of
Food Allergy in the United States. Report of the
NIAID-Sponsored Expert Panel. J Allergy Clin
Immunol 2010;126:S1–58.
23. Sicherer, SH, Sampson, HA. Auriculotemporal
syndrome: a masquerader of food allergy. J Allergy Clin
Immunol 1996;97:851.
24. Sampson HA. Food allergy. Accurately identifying
clinical reactivity. Allergy 2005;60(Suppl 79):19–24.
25. Romano A, Di Fonso M, Giuffreda F, et al. Diagnostic
work-up for food-dependent, exercise-induced
anaphylaxis. Allergy 1995;50:817–24.
26. Sicherer SH. Clinical implications of cross-reactive food
allergens. J Allergy Clin Immunol 2001 Dec;108(6):
881–90.
27. Rodriguez J, Crespo JF. Clinical features of crossreactivity of food allergy caused by fruits. Curr Opin
Allergy Clin Immunol 2002;2:233–8.

CHAPTER

7 

Pollen–Food Syndrome
Antonella Muraro and Cristiana Alonzi

Introduction
Pollen–food syndrome is a term describing associations between inhalant pollen allergies and allergic
manifestations on ingestion of particular fruits, vegetables and spices. Albeit first described as far back
as 1948, this kind of allergy has attracted special
attention during the last few decades because of the
steadily increasing prevalence of inhalant allergies
in recent years. So far, several clinical syndromes
have been described, such as birch–fruit, celery–
mugwort–spice and latex–fruit, which have a
molecular background consistent with pollen–food
syndrome. The term class II food allergy was coined
to describe the relationship between sensitivity to
certain foods and airborne allergens. In fact, two
different forms of immunoglobulin (Ig)E-mediated
food allergy can be distinguished (class I and class
II), based on clinical appearance, pattern of allergens, and underlying immunological mechanisms;
and in class I food allergies, the sensitization process
is assumed to occur via the gastrointestinal tract.
The class I type of food allergy mainly affects young
children and may be the presenting sign of atopic
syndrome. The most important allergens are cows’
milk, egg, and beans. The second type (class II),
which we discuss here, develops later in life and it
is believed to be the consequence of an allergic
sensitization to inhalant allergens. The basis for this
food allergy is an immunological cross-reactivity
due to a high amino acid sequence identity and
structural homology between food and pollen
© 2012, Elsevier Inc

allergens (i.e. even from botanically unrelated
plants).1 They are often called incomplete food
allergens or non-sensitizing elicitors. It is not always
possible, however, to distinguish clearly between
class I and II food allergens. Extreme thermostability and resistance to pepsin digestion identify lipid
transfer proteins (LTPs) as potent class I food allergens, whereas pollen LTPs reportedly behave as
primary sensitizing allergens in patients with IgE to
both mugwort and peach LTPs, indicating an
involvement of LTPs in class II food allergies as well.
These plant proteins are often referred to as
pan-allergens because they are widely distributed
throughout the plant kingdom and are involved in
the extensive IgE cross-reactivity between antigens
from unrelated plant species.2 Several families of
plant proteins have been shown to be involved
in pollen–food syndrome, including profilins,
pathogenesis-related proteins (PRs) and LTPs.
Cross-reactions can even occur between species that
are only remotely related phylogenetically, such as
birch and kiwi. In most of these cases the ‘oral
allergy syndrome’ (OAS) is the prominent clinical
symptom, but reactions may range in severity from
mild local symptoms to associated systemic symptoms involving distal organs, to a fatal outcome.
The severity of the reaction may depend on a variety
of factors, including the type of allergen, the amount
ingested, its digestion and uptake in the gastrointestinal system, and individual cofactors (e.g. concomitant viral infections, physical exertion, intake
of alcohol or drugs). Thermostable allergens of

Food Allergy

higher molecular weight seem responsible for more
severe reactions, e.g. LTPs.3
The increasing availability of allergen panels
derived from various sources enables a detailed
analysis of individual patients’ sensitization profiles – what has been termed ‘component-resolved
diagnostics’ (CRD). The rationale behind CRD is to
establish associations between specific IgE, measured by using individual allergen components (or
parts of them) and clinically relevant aspects of the
allergic disease.

Epidemiology
Pollen–food syndrome is the most frequent cause
of food allergies in adults and adolescents.2
Most allergic reactions against plant-derived
foods are strongly associated with several pollen
allergies. Approximately 15–20% of the populations in the developed world are allergic to pollen,
and 50–93% of patients allergic to birch pollen
have IgE-mediated reactions to pollen-related
foods. On the basis of these data, the prevalence of
fruit, nut and vegetable hypersensitivity can be estimated at significantly more than 1%. The overwhelming majority of pollen-related reactions to
fruits in Europe are associated with birch and hazel
nut pollen allergy. Cross-reactive allergies to certain
foods, for example apple, peach, tomato or peanut,
have also been found in a minority of individuals
with grass pollen allergy. Allergies to several foods
related to birch pollen (such as celery, carrot and
spices) can occur in patients allergic to mugwort
pollen but not to birch pollen, but some studies
have shown that this phenomenon is rare.4 Enrique
et al.5 reported an association between plantain
pollinosis and plant food allergy, with 50% of their
patients allergic to the pollen being allergic to at
least one plant. The foods most frequently implicated were hazelnuts, fruits (e.g. peach, apple,
melon and kiwi), peanuts, maize, chick peas, and
some vegetables (e.g. lettuce and green beans).
There are few reports of specific food allergies being
associated with wall pellitory (Parietaria) and trees
from the Oleaceae family, although these pollens
are common elicitors of pollen allergies in the
Mediterranean area, Liccardi et al.6 described associations between sensitization to pistachio and
Parietaria allergy. In 2002, Florido Lopez and coworkers evaluated 40 patients with Olea pollinosis

84

and adverse reactions to plant-derived foods (21 of
them with OAS, 19 with anaphylactic reactions): all
the patients were positive on the skin prick test
(SPT) against one or more Olea europaea allergens.
Sensitization to Ole e 7 (an LTP in Olea pollen)
was significantly more common in anaphylactic
patients, whereas sensitization to Ole e 2 (a profilin) was more frequent in the OAS group.7 Sensitization to Amb a 4, ragweed homolog of Art v 1, the
major pollen allergen of the composite plant
mugwort (Artemisia vulgaris) has been reported to
trigger reactions to the Cucurbitaceae family (watermelon, cantaloupe, honeydew melon, zucchini and
cucumber) and banana. So far the cross-reactive
allergens have not been characterized. However, the
pan-allergen profilin or glycoallergens or LTPs seem
involved in the clinical manifestations of this
ragweed–melon–banana association. Although the
symptoms are usually mild, patients with severe
systemic reactions have been described.1

Clinical presentation
Oral allergy syndrome: also known as
pollen–food syndrome
The most frequent symptom of food allergy,
particularly in adults, is the so-called OAS. This
has been demonstrated in double-blind placebocontrolled food challenge (DBPCFC) studies
involving hazelnut, apple and cherry allergies.8
OAS is a condition characterized by IgE-mediated
allergic symptoms restricted to the oral mucosa,
which may involve itching and vascular edema of
the lips, tongue, palate and pharynx. It is sudden in
onset and may be associated with itching of the ear
and a sense of tightness in the throat.9 Symptoms
usually develop within minutes and then gradually
fade within an hour. Although oral itching can be
elicited by any food allergen, the classic OAS is
associated with sensitization to heat- and pepsinlabile plant-derived proteins in patients with a
pollen-related food allergy, in which case crossreactivity between homologous plant-derived proteins in pollens and vegetable foods is the basis of
the syndrome.10
Most allergens involved in such cross-reactivity
reactions are easily destroyed by pepsin digestion
and heat, which explains why symptoms of pollenrelated food allergy are generally mild and the

Pollen–Food Syndrome

majority of patients with OAS have no problem if
they ingest the offending foods after cooking
or other heat treatments. OAS can also be induced
by stable allergens, so a subset of patients with
this specific type of food allergy may sometimes
experience generalized and even life-threatening
reactions.

Anaphylaxis
Pollen–food allergy syndrome is often associated
with systemic and severe reactions in addition
to OAS. This is the case when nsLTP, the most
important family of pollen stable allergens, is
involved. Patients may experience a generalized
life-threatening reaction within minutes of ingesting the food.11
Studies focusing particularly on celery and carrot
allergies in subjects allergic to pollens have reported
systemic reactions in approximately 50% of patients
according to case histories, and up to 50% of
patients experienced systemic reactions when challenged, even if the DBPCFC was performed using a
stepwise ‘spit and swallow’ protocol, which was
suspended at the lowest food dose reproducibly
causing symptoms.12 It has also been reported that
a member of the PR-10 protein family from soybean,
Gly m 4, can induce severe allergic reactions.13 Anaphylactic reactions are not rare in mugwort–birch–
celery syndrome.4
In conclusion, these studies demonstrate that the
symptoms of pollen-related allergy to certain foods
may be more severe than is commonly assumed.

Gastrointestinal disorders
The digestive tract can also be involved in pollinoses which can cause a Th2-mediated inflammatory response in the gut, and may even be
responsible for eosinophilic esophagitis, a disorder
characterized by a dense eosinophilic infiltrate with
squamous epithelial hyperplasia in the absence of
any gastric or intestinal mucosal anomalies. It has
been demonstrated that colonoscopic Bet v 1 challenge can induce intestinal inflammation in patients
with birch pollen allergy. Magnusson et al.14 have
concluded that in patients with birch pollinosis and
a birch + plant food syndrome, a duodenal biopsy
obtained during the pollination season shows a
greater eosinophil and mast cell infiltration than in
biopsies taken at other times of year.

7

Pan-allergens
As reported by Breiteneder and Ebner,15 plantderived proteins responsible for food allergy include
few protein families (Table 7.1). Many allergens
belong to the cupin (seed storage proteins) or
prolamin superfamilies (2S albumins, α-amylase
inhibitors, non-specific (ns)LTPs, and prolamin
storage proteins of cereals). The pathogenesisrelated proteins are a miscellany of 14 plant protein
families involved in plant resistance to pathogens
or adverse environmental conditions. Then there
are the profilins, a number of unrelated families of
structural and metabolic plant proteins. Several of
these proteins are widely distributed throughout
the plant kingdom and may consequently be
involved in extensive IgE cross-reactivity between
antigens from taxonomically unrelated plant
species, a phenomenon described in the panallergen theory.16 IgE cross-reactivity may be clinically manifest or irrelevant. The clinical signs seem
to be influenced by a number of factors, including
the host’s immune response and exposure to the
allergen, and the type of allergen involved. The proteins’ structural characteristics are major crossreactivity determinants, so pollen–food syndrome
develops as a consequence of shared features at
primary and tertiary protein structure level. It has
been claimed that proteins with >70% sequence
identity are often cross-reactive, whereas those with
<50% sequence identity rarely cross-react, although
there are a few exceptions. Other factors influencing
the clinical correlations of pollen–food syndrome
include allergen concentrations and their differential expression during ripening, and their stability
on cooking. A brief description of the cross-reactive
pan-allergens involved in pollen–food allergy
(Table 7.2) is given below.

The prolamin superfamily
The prolamin superfamily is the most prominent
of all the protein families with allergenic members,
including the nsLTP family, the 2S albumin storage
proteins, the cereal α-amylase/trypsin inhibitors,
and the soybean hydrophobic protein. Prolamins
are a group of seed storage proteins and the main
storage proteins in cereals and other members of
the grass family. They are stable in response to
thermal processing and enzyme proteolysis as they
are rich in cysteine. Since they were first described

85

Food Allergy
Table 7.1  Biological classification of the main vegetable food allergens. Allergen nomenclature: Act c (kiwi), Ana o
(cashew), Api g (celery), Ara h (peanut), Ber e (Brazil nut), Bra r (rapeseed), Cas a (chestnut), Cor a (hazelnut), Cuc m
(melon), Jug r (walnut), Lyc e (tomato), Mal d (apple), Pers a (avocado), Pru av (cherry), Pru p (peach), Pyr c (pear), Sec
c (rye), Ses i (sesame), Tri a (wheat). Adapted from Asero et al. Plant food allergies: a suggested approach to allergen-resolved
diagnosis in the clinical practice by identifying easily available sensitization markers. Int Arch Allergy Immunol. 2005; 138: 1–11.

Main vegetable
food allergens

Cupin
superfamily

2.2 Vicilins

Ara h 1, Ses I 3, Jug r 2, Ana o 1, Cor a 11

Legumins

Ara h 3–4, Jug r 4, Ana o 2, Cor a 9

Prolamin
superfamily

2S albumins

Ara h 2–6-7, Jug r 1, Ana o 3, Ric c 1–3, Sin a 1, Bra j 1, Ber e 1

Ns LTP

Pru p 3, Jug r 3, Cor a 8, Mal d 3,

α-amylase inh

Rice

Prolamins of cereals

Tri a 19, Sec c 20

Pathogenesis-related
protein

PR-2 (Hev b 2)

Defense
system
proteins (I)

PR-3 (Hev b 6.02, Pers a 1, Cas s 5)
PR-4 (Bra r 2)
PR-5 (Pru av 2, Mal d 2, Cap a 1, Act c 2)
PR-9 (Tri a Bd)
PR-10 (Mal d 1, Api g 1)
PR-14 (LTP)

Defense
system
proteins (II)

Thiol proteases

Papain-like cysteine proteases (Act c 1) Gli (Gly credo) m Bd
Subtilisin-like serine proteases (Cuc m 1)

Protease inhibitors

Type Kunitz (soy)
α-amylase inhs (cereals)

Structural and
metabolic
proteins

Storage proteins

Patatin (Sola t 1)

Enzymes

Phenylcoumaran benzyl eth. reductase (Pyr c 5)
Cyclophilin (carrot)
Oxydases (Api g 5)
Liases (garlic)

Profilins

in 199917 they have been the object of considerable
research in view of their clinical relevance.

Lipid transfer proteins
LTPs are members of the prolamin superfamily
(PR-14) with low-molecular-weight proteins (9–
10 kDa) and are contained in large amounts (as
much as 4% of the total soluble proteins) in higher
plants. LTPs are characterized by a conserved pattern
of 6–8 cysteines, forming three to four disulfide
bridges. They are named after their capacity to
transfer lipids between membranes. More than 100
plant nsLTPs have been sequenced. Plant LTPs have
a total number of amino acids varying from 91 to
86

Api g 4, Mal d 4, Ara h 5

95 residues and exhibit strong structural homologies.18 Nevertheless, no sequence homology has
been found between LTPs from mammalian and
plant LTPs.
LTPs are important food allergens, especially in
Mediterranean areas. In northern and central
Europe, fruit allergies are mainly described as a
cross-reactive phenomenon resulting from sensitization to homologous allergens from (birch)
pollen, and patients usually have only mild symptoms restricted to the oral cavity (OAS), whereas
patients in Mediterranean countries also suffer
from fruit allergies unrelated to pollens and frequently have systemic reactions. The nsLTPs have
been suggested as a model allergen for true food

Pollen–Food Syndrome

7

Table 7.2  Class II food allergens. Adapted from Mothes N, Horak F, Valenta R. Transition from a botanical to a molecular
classification in tree pollen allergy: implications for diagnosis and therapy. Int Arch Allergy Immunol. 2004; 135: 357–373.

Allergen

kDa

Family

Cross-reactivity
Source

Bet v 1

17

PR-10

Molecule

Fruits:
  Apple

Mal d 1

  Cherry

Pru av 1

  Apricot

Pru ar 1

  Pear

Pyr c 1

Vegetables:
  Celery

Api g 1

  Carrot

Dau c 1

  Soybean

Gly m 4

Nuts:
  Hazelnut

Cor a 1

  Peanut

Ara h 8

Others:
  Parsley

Pc PR 1 and 2

  Spices
Bet v 2

14

Profilin

Fruits:
  Cherry

Pru av 4

  Peach

Pru p 4

  Pear

Pyr c 4

Vegetables:
  Celery

Api g 4

  Tomato

Lyc e 1

  Soybean

Gly m 3

  Potato
Others:

LTP

9

PR-14

  Spices

Cap a 2

  Latex

Hev b 8

Fruits:
  Apple

Mal d 3

  Apricot

Pru ar 3

  Peach

Pru p 3

  Plum

Pru d 1

Others:
  Corn
TLP

23–31

PR-5

Zea m 14

Fruits:
  Apple

Mal d 2

  Cherry

Pru av 2

  Kiwi

Act c 2

87

Food Allergy

allergy19 because of their high resistance to heat
treatment and proteolytic digestion. Sensitization
to LTPs has also been reported in patients with no
pollen allergies, which supports their role as a sensitizing food allergen. LTPs were first identified by
Lleonart20 and his group in 1992, who discovered
a low-molecular-weight (~10 kDa) allergen in
peach skin that later turned out to be the nsLTP
recently designated Pru p 3. In the last 15 years,
several studies have shown an immunologic crossreactivity within LTPs from Rosaceae17 and between
LTPs from Rosaceae and botanically unrelated
plant-derived foods.21 The spectrum of foods in
which the role of LTP as an allergen is being studied
is increasing rapidly. IgE antibodies against food
LTPs have been shown to express variable degrees
of cross-reactivity, which has been identified
between LTPs in latex and some pollens (e.g. Par j
1 and Par j 2, the major Parietaria allergens, are
LTPs) as well. Peach seems to be responsible for the
primary sensitization to this allergen (as no patients
allergic to LTPs but not sensitized to peach have
been described to date) and the cross-reactivity to
LTPs of botanically unrelated plant foods seems to
depend on the level of peach LTP-specific IgE (as in
class I allergies).22,23 This finding has been questioned, as in some patients with mugwort pollinosis it appears that the antigenicity common to
mugwort and peach LTP was due primarily to
mugwort pollen (i.e. a class II food allergy).24

CLINICAL CASE
A 10-year-old girl reported tingling and pruritus of the lips,
mouth and oropharynx after ingestion of peach, carrot,
apple, cherry and tomato. The symptoms appeared less
than 5 minutes following the ingestion of these foods,
were mild and subsided spontaneously in less than 15
minutes. She had never had gastrointestinal or respiratory
complaints. The girl was already on an elimination diet for
these fruits and vegetables, both raw and cooked. From
the age of 4 years she had suffered from rhinitis and
asthma with sensitization to grass pollen, Bermuda grass,
birch and hazel pollen. In vitro specific IgE tests show the
following results:
Tomato
Carrot
Apple
Peach
Cherry
Birch
Hazel
Olive
Grass
88

8.0 kU/L
29.9 kU/L
37.7 kU/L
47.3 kU/L
25.5 kU/L
>100 kU/L
>100 kU/L
89.5 kU/L
>100 kU/L

Prick-by-prick test with fresh fruits and vegetables was
positive for peach, cherry and carrot, but negative for
tomato as evaluated in mm wheal/erythema.
Peach
Cherry
Tomato
Histamine

3/6
5/10
Neg
4/20

Carrot
Apple

5/10
7/10

Neg control

Neg

Discussion
The most important challenge in pollen–food syndrome is
to identify those patients with a high risk for systemic
reactions.
Considering that the girl had a positivity to birch
(>100 kU/L), apple, cherry and peach, which belong to the
Rosaceae family, it is important to investigate the presence
of IgE antibodies to Bet v 1 and nsLTP to evaluate the risk
for serious systemic reactions.
Bet v 1 is the major allergen component found in birch
pollen, which belongs to a group of plant proteins termed
pathogenesis-related protein family number 10 (PR-10),
sensitive to heat and proteases. Bet v 1 is correlated with
symptoms restricted to the mouth.
nsLTP (non-specific lipid transfer proteins) are very
stable allergens widespread in plants. The important
characteristic of nsLTP is the high resistance to heat
and protease, correlated with severe clinical symptoms,
such as urticaria/angioedema, asthma and anaphylaxis.
CRDs evaluation has shown:
Bet v1
Peach LTP (Pru p 3)

>100 kU/L
0.16 kU/L

Conclusion
The time course of the pollen and food allergies suggests
a primary sensitization through the inhalation route to
pollen with the generation of cross-reactive IgE to pollen
profilin.
Considering these results, we can suppose that the patient
will have only oral symptoms (oral allergy syndrome).
Furthermore, the reactions are only induced by fresh fruits
and the processed fruits and vegetables, such as
commercial fruit juices, peach in syrup or cooked foods are
tolerated.

Pathogenesis-related proteins
PRs form a heterogeneous collection of 14 plant
protein families. They are not a protein superfamily
but a set of unrelated protein families that function
as part of the plant defense system.

Pollen–Food Syndrome

Proteins homologous to Bet v 1
About 98% of patients allergic to birch pollen are
sensitized to the major allergen Bet v 1, an 18-kDa
PR-10, and proteins homologous to Bet v 1 have
been detected in a number of plant-derived foods.
Bet v 1 is a member of the PR-10 family.
Approximately 70% of individuals allergic to
birch pollen suffer from pollen–food syndrome
and have IgE cross-reactivity to Bet v 1 and its food
homologs.15 The taxonomic distribution of allergens related to Bet v 1 is fairly limited. Pollen allergens are found exclusively in the birch and beech
families, whereas the food allergens described come
from fruits in the Rosaceae families (including
apple, pear, peach, cherry, plum, apricot and
almond), and vegetables in the Apiaceae (including
celery, carrot, fennel and parsley) and Fabaceae
(peanut and soybean). The cross-reactivity of Bet v
1 with the major apple allergen Mal d 1 occurs not
only at B-cell but also at T-cell level. Bet v 1 also
contains the major T-cell activating region of Api g
1, confirming that Bet v 1 is responsible for initializing an allergic response to the major celery allergen. The epitopes of the hazelnut allergen Cor a
1.04 appear to be less related to the hazel pollen
allergen Cor a 1 than to the Bet v 1 from birch
pollen. Virtually all patients allergic to birch pollen
are positive by SPTs with many of these fresh fruits
and vegetables, but only a proportion of them have
food allergies (generally those reporting severe
allergy-related respiratory symptoms or showing
the highest levels of birch pollen-specific IgE). This
is particularly true of allergies to vegetables that are
botanically distant from Rosaceae, such as those of
the Apiaceae. Many vegetable food proteins homologous to Bet v 1 (and those from fruits of the
Rosaceae in particular) are extremely labile and
easily destroyed by heat, oxidation, extraction procedures and pepsin digestion. Clinically, this translates into a good tolerance of heat-processed foods
and commercial fruit juices, and the symptoms of
a reaction rarely amount to more than OAS. Not all
Bet v 1-homologous proteins are equally heat- and/
or pepsin-sensitive, however: celery (Api g 1) and
soybean (Gly m 4) antigens have been reported to
cause severe systemic symptoms.
Celery allergy is common in Europe, and reportedly a major cause of food-induced anaphylaxis in
Switzerland.25 Heating does not change its allergenicity. Birch and mugwort pollens are known to
be cross-reactive to celery and are considered

7

sensitizing antigens. Whereas the allergens in celery
also include Api g 4 and Api g 5, the major allergen
is Api g 1, which belongs to the above-mentioned
PR-10. The reason why Api g 1 is stable on heating
– unlike other allergens in the same group, such as
Bet v 1 – remains to be thoroughly clarified.
In 2002, Kleine-Tebbe et al.13 reported that 20
patients with birch pollinosis developed allergic
symptoms, including anaphylactic shock, soon
after the initial ingestion of soybean protein. Their
symptoms included facial swelling (17 patients),
OAS (14 patients), dyspnea (six patients), urticaria
(six patients) and drowsiness (five patients), and
occurred within 20 minutes of their first taste of the
soy product. The majority of patients reported
symptoms during the tree pollen season. The
authors produced a very pure recombinant SAM22
protein (Gly m 4) to prove the hypothesis that a
pollen-related allergen in soybean was responsible
for the allergic reactions to the food product. They
concluded that there was strong evidence to suggest
that a protein from soy related to birch pollen
could trigger adverse reactions to soy in patients
with high IgE titers to Bet v 1. A follow-up study by
Mittag et al.26 confirmed that Gly-m-4-specific IgE
testing was positive in 21 of 22 birch pollinosis
patients who developed soybean allergy, and that it
inhibited IgE binding to soybean protein by 60%
or more in nine of 11 patients, indicating that Gly
m 4 was the major allergen. Moreover, as the
binding of IgE to soybean protein was inhibited by
80% or more after adding birch pollen protein in
nine of the 11 patients, the authors suggested that
birch pollen is the main culprit responsible for the
antigenicity shared by the two allergens. According
to their report, the Gly m 4 content in soybean
increased during ripening and storage, and was no
longer detectable in highly fermented soy foods
(e.g. miso and soy sauce) or roasted soybeans,
whereas it was still detectable in tofu, soy flakes,
and a dietary powder containing soybean. Gly m 4
also revealed a certain degree of stability to moderate heating, i.e. its content in soybeans was reduced
after 30 minutes of cooking, but it was only after 4
hours of cooking that no Gly m 4 was detectable.

Thaumatin-like proteins (TLPs)
TLPs are members of the PR-5 family. Thaumatin is
highly water-soluble and stable on heating and
under acidic conditions.
89

Food Allergy

Mal d 2 is an important allergenic TLP in apple
that is associated with IgE-mediated symptoms in
individuals with apple allergy. Purified recombinant Mal d 2 displayed the ability to bind IgE
from individuals with apple allergy in the same way
as natural Mal d 2. The TLP of sweet cherry, Pru av
2, has also been identified as a major allergen, and
a grape TLP with an amino acid sequence very
similar to that of Mal d 2 and Pru av 2, and a kiwi
TLP described as the allergen Act c 2, have been
identified as minor allergens.

Profilins
Profilin is a monomeric, largely cross-reacting 12–
15-kDa actin-binding and cytoskeleton-regulating
protein contained in all eukaryotic cells.27 Allergenic
profilins are found exclusively in flowering plants
and are minor pollen allergens. Several studies have
shown that only 10–20% of patients with pollen
allergy are sensitized to profilins, but they react to
a broad range of inhalant and food allergens. Actually, profilins form a family of highly cross-reactive
allergens in monocot and dicot pollens, plant foods
and Hevea latex. An example of profilin is the birch
pollen allergen Bet v 2. Patients sensitized to Bet v
2 or to grass pollen profilin often have oral symptoms on ingesting apple, pear, carrot and celery, in
response to IgE cross-linking by the homologous
profilins contained in these foods.15 In the mugwort–
celery–spice syndrome, patients sensitized to
mugwort cross-react to the profilins in celery and
spices of the Apiaceae, or Umbelliferae, family
(carrots, caraway seeds, parsley, coriander, aniseed
and fennel seeds).1
Although many pollen–food syndromes are
related to profilins, it is difficult to purify natural
profilins from fruit and vegetables, and only a few
isolated recombinant profilins have been described.
Asero et al.28 performed skin tests in 200 pollinosis
patients using purified palm profilin (Pho d 2) and
observed a positive reaction in one-third, who were
also positive to pollens from a wide range of plants;
more than half of them also exhibited OAS, with
fruit allergy symptoms and no symptoms on ingesting cooked or processed foods.

Cross-reactive carbohydrate
determinants (CCDs)
The N-linked carbohydrate groups of glycoproteins
induce IgE, leading to cross-reactivity between
foods and pollens.29
90

Carbohydrates with an IgE-binding capacity have
also been reported in plant proteins with no allergenicity, e.g. bromelain in pineapple, horseradish
peroxidase, polyamine oxidase in corn, ascorbic
acid oxidase in Cucurbita pepo, and phytohemagglutinin in haricot bean.1
Cross-reactive IgE directed against the glycosyl
portion of glycoproteins seem to have a poor biological activity. Many CCDs are monovalent and do
not form bridges of IgEs on the mast cells, so they
are generally assumed not to induce histamine
release. The identification of anti-CCD IgE will
improve allergy diagnostics in vitro by discriminating specific IgE positive to foods without any apparent clinical significance in patients sensitized to
pollen.
Because of the variable biological activity of
cross-reactive IgE in relation to carbohydrates, the
debate over their importance in allergy remains
open.

CLINICAL CASE
A 10-year-old girl with a history of mild to moderate atopic
dermatitis, allergic asthma and rhinitis and food allergy for
kiwi was admitted to the pediatric allergy clinic for a
reaction to hazelnut, with angioedema of the lips and
itching in her mouth. She reported having experienced the
same symptoms 2 weeks as well as 1 year before the
current episode which did not require medical
intervention.
She had suffered from a cows’ milk allergy until 5 years of
age and subsequently developed multiple sensitizations to
grass pollen, birch and hazel pollen, and dust mites.
The diagnostic work-up included prick-by-prick testing, in
vitro specific IgE tests and evaluation of relevant CRDs.
Prick-by-prick test results (wheal and erythema size in mm)
Cashew
Pistachio
Sesame
Hazelnut
Brazil nuts
Walnut
Peanut
Histamine
Control

3/5
4/20
3/15
Negative
Negative
Negative
Negative
3/20
Negative

Specific IgE results
Timothy grass
Orchard grass
Perennial ryegrass
Velvet grass
Birch
Hazel
Bet v 1

27.40 kUa/L
34.10 kUa/L
41.50 kUa/L
36.90 kUa/L
46.10 kUa/L
38.00 kUa/L
52.40 kUa/L

Pollen–Food Syndrome

Diagnosis

Specific IgE results
Profilin
Bet v 4
Sesame
Peanut
Hazelnut
Brazil nut
Cashew
Pistachio
Walnut
Kiwi
rCor a 8 LTP hazelnut
rCor a 1 PR-10 hazelnut
rAra h 8 PR10
rAra h 1 peanut
rAra h 2 peanut
rAra h 3 peanut

<0.10 kUa/L
0.18 kUa/L
1.31 kUa/L
0.50 kUa/L
39.60 kUa/L
0.69 kUa/L
2.68 kUa/L
4.14 kUa/L
4.99 kUa/L
4.97 kUa/L
0.79 kUa/L
39.00 kUa/L
4.54 kUa/L
<0.10 kUa/L
0.20 kUa/L
<0.10 kUa/L

Discussion
In this case the patient was positive for birch and hazel
pollen and for hazelnut, but prick-by-prick testing with
fresh hazelnut was negative. Moreover, the specific IgE for
Bet v 1 and rCor a 1 PR-10 hazelnut was very high,
whereas rCor a 8 LTP hazelnut IgE resulted very low.
Bet v 1
Hazel
Hazelnut
rCor a 1 PR-10 hazelnut
rCor a 8 LTP hazelnut

7

52.40 kUa/L
38.00 kUa/L
39.60 kUa/L
39.00 kUa/L
0.79 kUa/L

The major allergen from hazel pollen, Cor a 1, a Bet v 1
homolog, was reported to have similar IgE-binding
properties as the major hazelnut allergen.
Bet v 1 (the major birch pollen allergen) is a pathogenesisrelated protein that is responsible for oral allergy
syndrome (OAS) in patients with birch pollinosis and was
strongly correlated with apple, peach, hazelnut and carrot.
Patients allergic to birch and hazel pollen may have
symptoms to hazelnut.

Conclusion
In patients sensitized to Rosaceae food allergens or having
clinical symptoms to Rosaceae foods, it is important to
investigate the presence of IgE antibodies to Bet v 1 and
nsLTP to evaluate the risk for severe systemic reactions.
Bet v 1 homologs, unlike nsLTPs, are often associated with
local symptoms (OAS) and rarely with life threatening
reactions. In spite of this, it could be misleading to predict
a clinical reaction only on the basis of positivity to Bet v 1
above all, in the presence of high concentration of IgE
antibodies to this recombinant allergen.
In this light an oral food challenge with hazelnut should
strongly be considered.

The class II food allergy is difficult to diagnose and
currently available diagnostic tools are inadequate,
mainly because commercially available food extract
preparations are generally not suitable for performing diagnostic tests. The major allergens involved in
this type of food allergy are susceptible to degradation processes and are easily destroyed during the
extraction procedure. Recombinant DNA technologies have enabled a number of these allergens to be
produced in a pure and stable form, and several
recombinant allergens involved in class II food
allergies have been tested for their suitability for use
in in vivo and/or in vitro diagnostic process. The
use of these molecules should lead to important
advances, moving on from an extract-based diagnosis to a CRD, which may provide refined information on cross-reactivity patterns and the potential
severity of symptoms. Molecular analysis of allergen sensitization patterns may help us to improve
the predictive and prognostic power of allergy diagnostics based on IgE antibodies.
In northern European populations, for example,
sensitization to Rosaceae fruits is characteristically
directed against Bet v 1-related food allergens and
the symptoms are usually mild, but in the Mediterranean area (where sensitization to Rosaceae is
mainly related to nsLTPs) is often accompanied by
systemic food reactions.8 Although certain allergens
are known to be strongly predictive of manifest
allergic disease, others (typically cross-reactive
determinants such as profilins or particular glycan
structures) are considered only weakly associated
with clinical reactivity. Given its use of purified
natural or recombinant allergen molecules rather
than crude natural extracts,30 an intrinsic advantage
of CRD lies in its higher diagnostic sensitivity,
which has been demonstrated in several cases. The
use of such potent reagents in routine diagnostic
tests would have a positive effect on their diagnostic
efficacy in clinical practice.
In vivo, SPT, oral food challenges (open and
DBPCFC), and in vitro tests (food-specific IgE assay
and basophil studies) are primary tools for the
diagnosis of food allergy in daily practice (Fig. 7.1).

In vivo tests
Prick test
For plant-derived foods, commercial extracts for use
in SPT have a limited sensitivity and give rise to
91

Food Allergy
History suggestive of pollen–food syndrome

Confirmed by SPT
with fresh material
and/or specific IgE

Not confirmed by SPT
with fresh material
and/or specific IgE
Oral challenge

Clinical features:

Clinical features:

OAS

Systemic reactions

Both labile and
stable allergens
are suspect

Stable allergens
are suspect

IgE to Bet v 1
positive

IgE to Bet v 1/2
positive

IgE to LTP positive

IgE to seed storage
protein positive

Sensitization
to Bet v 1-like
allergens

Sensitization to both
Bet v 1-like allergens
and profilin

Sensitization
to LTP (Pru p 3)

Sensitization to
storage protein

Evaluate for potential
cross-reactivities

Evaluate for potential
cross-reactivities

No oral challenge

No oral challenge

No oral challenge

No oral challenge

No epinephrine

No epinephrine

Carry epinephrine

Carry epinephrine

Figure 7.1  Proposed diagnostic algorithm for patients with suspected pollen–food syndrome.10

high false-negative rates. Most allergens involved in
class II food allergy are easily degraded during the
extraction process. The enzymes are released during
the mechanical crushing of the food and certain
allergens may be degraded even before extraction
begins. The degradation may also continue during
lengthy periods of storage, thereby progressively
changing the composition of the initial food extract.
The final amount of an allergen in an extract
depends on the raw material used and the method
adopted to extract the proteins. For instance, an
optimal content of LTP is achieved when they are
92

extracted from fruit peel or skin. On the other
hand, using this approach will mean that allergens
belonging to the PR-10 family and profilins will be
under-represented in the final extract, because they
are located mainly in the flesh of fruits. The same
problem applies to the pH conditions during the
extraction process. Whereas optimal amounts of
PR-14 family proteins are obtained under slightly
acidic conditions, members of the PR-10 protein
family are ideally extracted at a pH of 8.6. In addition, different plant strains may contain different
quantities of allergens, as shown in the case of

Pollen–Food Syndrome

apples.31 The standardization of food extracts by
total protein content, single allergen content or
allergenic activity is therefore unfeasible in many
cases. Several attempts have successfully been made
to improve this situation. Unfortunately, these
approaches demand complex extraction procedures
so they are not suitable for use in the routine preparation of food extracts.
Skin testing with native foods using the prickprick technique clearly produces better results. In
this test, the lancet is plunged several times into the
peel and/or flesh of the food immediately before
pricking the patient’s skin. This is currently the
most reliable in vivo test as far as labile allergens
are concerned (e.g. fruit and vegetables). Prick-prick
tests are also useful when there are discrepancies
between a suggestive case history and a negative
SPT result obtained with a commercial extract, or
when a specific food extract is unavailable. The
main drawbacks of the prick-prick test are the low
specificity, resulting in high false positive rates, and
the impossibility of standardizing the source of the
allergen. Among other reasons, the test’s limited
specificity is also an expression of IgE cross-reactivity
with pollen or other related foods, and the only
way to ascertain the clinical relevance of positive
SPT findings is by means of controlled oral challenges. As the concentration of labile allergens in
commercial extracts of plant-derived foods falls
considerably whereas the stable allergens persist,
it has been suggested that this observation be
exploited for the differential diagnosis between
patients sensitized to stable (e.g. LTP, seed storage
proteins etc.) versus labile (e. g. Bet v 1-like, profilin) allergens.10
When recombinant Api g 1, the major allergen of
celery, was used in skin tests, the results indicated
that this protein enabled an accurate in vivo diagnosis of celery allergy in areas where birch trees are
common.32 Very recently, taking cherry as a model
food, a panel of three recombinant allergens (Pru
av 1, Pru av 3, and Pru av 4) was tested for their
ability to diagnose cherry allergy by SPT by comparison with DBPCFC. The commercially available
cherry extract prompted a positive skin prick
response in 20% of cases, whereas the panel of
recombinant proteins reached a sensitivity of 96%.

Food challenges
Besides all the difficulties of obtaining a reliable
serological diagnosis of class II food allergy, oral

7

provocation tests may also produce questionable
results. In this respect, the diagnosis of OAS is particularly difficult to handle, as the food should not
be swallowed immediately but kept in the mouth
for a certain time. The oral challenge is a diagnostic
test that usually provides strong evidence of a food
allergy, and enables clinicians to recommend suitable dietary restrictions.
Oral food challenges may be performed in open
or single-blind fashion, or as a DBPCFC, which is
usually considered the gold standard for diagnosing food allergies. Owing to the ‘instability’ of most
class II food allergens and their rapid degradation
by endogenous enzymes in the food, truly allergic
patients may have a negative response to the probe
of the DBPCFC but react positively to an open
challenge with the fresh food. Different challenge
models may also differ in sensitivity and the
number of placebo reactions. Additional problems
concern how to find suitable ingredients to conceal
the food being assessed in the meal used for the
challenge, so as to minimize the patient’s subjective
bias. In 2000, Ballmer-Weber developed a two-step
‘spit and swallow’ protocol to verify allergies to
celery, carrot and cherry. The patient must initially
retain the allergen in increasing amounts in his
mouth, spitting it out after 1 minute. The amount
is doubled every 15 minutes. After an interval of 1
hour, the procedure is repeated with a placebo. If
patients consistently report OAS symptoms three
times in response to the allergen, but not to the
placebo, they are regarded as responders. Patients
who complain of no symptoms during this spitting
phase go on to step 2 of the DBPCFC, in which they
ingest the allergen in increasing amounts at
15-minute intervals. Between the two steps of the
challenge there must be an interval of at least 24
hours. This protocol not only considers the specific
clinical features of OAS but is also safer for the
patients. The need for standardized challenge
models and suitable recipes for challenge and
placebo preparations nevertheless remains.

In vitro tests
Allergen-specific IgE antibodies are the main components of food allergy reactions. They are easy to
measure in blood samples from individuals suspected of having a food allergy using commercially
available assays, and assessing specific IgE is a frequently used important element in the clinical
investigation and diagnosis of food allergy. In vitro
93

Food Allergy

allergen-specific IgE tests (including the radio­
allergosorbent test (RAST) and the enzyme allergosorbent test (EAST)) are used to test serum for
IgE-mediated food allergies.
Commercial ImmunoCAP extracts have a low
diagnostic sensitivity in pollen–food syndrome.
Several studies based on the CRD concept using
pure allergen molecules have been published.
Using recombinant Pru av 1 and Pru av 4, EAST
revealed 97% positive results in 101 patients allergic
to cherry, as opposed to only 17% identified by
CAP/RAST.33
Sera from 43 patients with DBPCFC-proven
allergy to hazelnuts were investigated with either
hazelnut extract or recombinant major allergen Cor
a 1.0401.34 EAST with recombinant Cor a 1.0401
yielded a sensitivity of 95%, as opposed to 70%
obtained with the commercially available CAP/
RAST system, which is based on a total food extract.
Ballmer-Weber et al.35 examined the IgE antibody
response in carrot allergy in 40 patients carefully
selected according to their clinical history, specific
IgE and a positive DBPCFC result. Two isoforms
of Dau c 1 (Dau c 1.0104 and Dau c 1.0201), the
profilin Dau c 4 and a reagent for CCDs were
used to assess sensitization, and the birch pollen
allergens Bet v 1 and Bet v 2 were used for comparison. The results confirmed that Dau c 1 is a major
allergen in carrot allergy. Although sensitization to
the Dau c 1.0104 isoform was more prevalent
among the individuals studied, the Dau c 1.0201
isoform showed the best correlation to the clinical
situation.
Gly m 4 and Ara h 8 have recently been identified
as Bet-v-1-related molecules in soybean and peanut,
respectively, and they have been produced in
recombinant form.26 In addition to extending the
panel of soybean and peanut allergens, Gly m 4 in
particular has prompted a marked improvement in
diagnostic sensitivity when used as an ImmunoCAP
reagent. Whereas only 10 of 22 individuals (45%)
with pollen-related allergy to soybean tested positive with the soybean extract-based test, all but one
(96%) showed IgE binding to rGly m 4 coupled
with streptavidin-coated ImmunoCAP tests.
Asero et al.22 suggested that peach LTP (Pru p 3)
could be important as a general marker of allergies
to plant-derived food. Studying 40 patients with
LTP reactivity, they found a correlation between
specific IgE levels to Pru p 3 and the extent of clinical reactivity to an increasing number of plantderived foods. Bolhaar et al.36 described cases of
94

severe reactions to Sharon fruit and identified
homologs of Bet v 1 and Bet v 2 as the main IgEbinding molecules in Sharon fruit extract. The
results of mediator release experiments conducted
with Bet v 1 and Bet v 2 led indirectly to the conclusion that Bet v 1-related structures, but not profilins, were biologically active allergens in Sharon
fruit and responsible for the clinical reactivity to
this food.36

Basophil activation test
Skin and serological assays indicate sensitization
but are not clinically relevant to IgE reactivity. Information on the biological function of observed IgE
reactivity can be obtained by means of the basophil
activation test (BAT), which has been used in a
number of clinical studies on plant food allergy
and CRDs. There are reports of BAT flow cytometry
being of diagnostic value in allergies to airborne
allergens (pollen and house dust mites), hymenoptera venoms, drugs (muscle relaxant allergy and
β-lactams), food and latex. For pollen-associated
food allergy the method has been evaluated in only
a few studies. Erdmann and collaborators37 focused
on a panel of Bet v 1 homologs from apple, carrot
and celery (respectively Mal d 1, Dau c 1.01 and Api
g 1.01), also considering Bet v 1 and Bet v 2 for
comparative purposes. A functional BAT with pure
allergen molecules was compared with ImmunoCAP™ measurements using whole allergen extracts,
revealing clinical sensitivities and specificities of
60–75% and 64–86%, respectively, for the IgE assay
and 65–75% and 68–100%, respectively, for the
BAT assay. The patients were not selected on the
basis of challenge tests, and unlike in the BallmerWeber35 study, no control group (patients with birch
pollen allergy without food allergy) was included in
the evaluation of the test’s diagnostic performance.
The authors concluded that, although a better characterization of the study participants would have
been useful, the use of CRD and the inclusion of
biological assays such as BAT might help to identify
the clinically most relevant allergens for in vitro
tests. Bet v 1 and Bet v 2 have also been included in
a CRD study dealing with grass pollen allergy.
Recording detailed case histories and determining
IgE reactivity to various pollen extracts and recombinant birch pollen allergens helped to identify different subsets of individuals allergic to grass pollens,
with or without food allergies, and with or without
co-sensitization to birch pollen allergens.

Pollen–Food Syndrome

Recombinant food allergens have improved our
knowledge of the chemical and immunological features of these proteins and given us a better idea of
the immunological mechanisms underlying class II
food allergies, but this is not enough. Data on the
use of recombinant allergens strongly support the
conviction that they are molecules suitable for
replacing food extracts in the future. But positive
serological test and SPT results do not necessarily
reflect a clinically relevant food allergy. The finding
of allergen-specific IgE does not always correlate
with symptoms when a given food is ingested.
So, in the end, although recombinant food allergens improve the reliability and accuracy of the
diagnostic material to use in SPT and serological
assays, the gold standard for confirming clinical
symptoms against certain foods remains the oral
food challenge.

Management
There is no agreement among clinicians on how to
manage pollen–food syndrome. One survey among
allergists found that 53% recommended complete
avoidance of the offending foods, 38% reported
giving recommendations tailored to each patient,
and 9% did not advocate food restrictions; 4% of
the clinicians recommended avoiding potentially
cross-reactive foods.38 Several studies have assessed
cross-reactivity, particularly in the Rosaceae family
of fruits: from 46% to 63% of patients with confirmed pollen–food syndrome to one fruit revealed
a clinical reactivity to other Rosaceae fruits.39 Based
on these studies and others, Rodriguez et al.39 recommended that, if a reported reaction is confirmed,
tolerance to other Rosaceae fruits (particularly
apricot, apple and plum) should be assessed unless
patients have already eaten them without developing any symptoms at any time after their initial
reaction.
Patients with pollen–food syndrome generally
tolerate cooked forms of the fruit or vegetable to
which they are allergic, and allergists often recommend that they cook reactive fruits and vegetables
before ingesting them.40,41 Thermal processing of
PR-10-like food proteins induces a denaturation of
the proteins and a disruption of their conformation
that translates into a loss of IgE-binding capacity,
thereby making these foods clinically tolerable.
Bohle et al.41 found that food allergens soon lost
their capacity to bind IgE and cause mediator

7

release after cooking, but these same cooked food
allergens retained their ability to stimulate Bet-v-1specific T cells.40,41 T-cell epitopes are short, linear
peptides that tend to survive gastrointestinal digestion and thermal processing.40 This may be important for several reasons. One is that patients with
atopic dermatitis and pollen–food syndrome who
eat cooked fruits and vegetables may experience an
exacerbation of their atopic dermatitis due to the
activation of Bet v 1-specific T cells that can migrate
to the skin and induce effector responses.40 Second,
the ingestion of cooked fruit and vegetables may
cause perennial pollen-specific T- and B-cell activation, leading to perennially increased allergenspecific IgE levels in patients allergic to pollen even
outside the pollen season.41 Pollen allergy is often
treated with subcutaneous immunotherapy. Because
the clinical symptoms of pollen–food syndrome
relate to a cross-reactivity between food allergens
and pollen IgE, it has been hypothesized that
immunotherapy for pollen allergy may treat pollen–
food syndrome too. Several studies have addressed
this issue with regard to birch pollen and pollen–
food syndrome, with varying results. Asero42 conducted one of the most successful studies, in which
84% of patients who were sensitive to birch pollen
and had pollen–food syndrome in relation to apple
reported a significant reduction or the disappearance of their oral symptoms in response to apples
after being treated with birch pollen subcutaneous
immunotherapy. In addition, 88% of these patients
showed a marked reduction in their reactivity to
SPTs with apple.42 In another study, 87% of birchallergic patients with pollen–food syndrome who
were treated with subcutaneous immunotherapy
could eat significantly more apple or hazelnut
without developing allergic signs or symptoms,
though the amount of apple or hazelnut they tolerated was still small.43 In contrast to the above
studies, Moller44 found no significant improvement
in food allergy symptoms during a course of subcutaneous or oral birch pollen immunotherapy in
a group of children with birch pollen allergy and
pollen–food syndrome compared with a control
group, although the treatment group’s pollenrelated rhinoconjunctivitis improved substantially.
In another study on birch subcutaneous immunotherapy and apple allergy, two of 12 patients
developed pollen–food syndrome and five of 12
developed IgE to Bet v 2 at some point during the
therapy,45 whereas there was no evidence of pollen–
food syndrome or Bet v 2 IgE in controls not
95

Food Allergy

submitting to birch immunotherapy. The authors
concluded that the treatment could induce allergies
to additional components in the pollen immunotherapy preparations that might cause new symptoms (e.g. pollen–food syndrome).45
Other investigators examined the effects of
sublingual immunotherapy with birch pollen
on pollen–food syndrome to apple to ascertain
whether administering birch pollen directly at the
site of food allergy symptoms might enhance the
treatment’s efficacy against pollen–food allergy. No
improvement in oral symptoms to apple ingestion
was seen in nine patients whose scores for nasal
reaction to birch pollen improved after sublingual
immunotherapy.46 The debate therefore continues
on the therapeutic benefits of pollen immunotherapy in pollen–food syndrome.

Conclusions
The pollen–food syndrome is increasingly common
and should always be considered in patients with
pollinosis. The clinical manifestations range from
mild symptoms, limited to the oropharynx, to
more severe reactions resulting in anaphylaxis. The
management of the food pollen-related symptoms
depends on the type of offending allergen. When
labile allergens are the triggers of the reaction the
cooked food can be tolerated and exclusion of raw
fruits and vegetables only is required. However, this
is also questioned, as some cooked labile food
allergens can retain their ability to activate pollenspecific T cells at the gastrointestinal tract, inducing
exacerbations of chronic symptoms. In addition,
when nsLTPs are involved, instructions to peel the
fruit and vegetables as well as managing severe reactions should also be provided.
The role of immunotherapy is still controversial
in spite of some promising results with subcutaneous immunotherapy in birch sensitive patients
with reactions to apple or hazelnut. The use of
component-resolved diagnostics (CRD) in characterizing the specific IgE profile of the patient has
proved to be a promising approach that in the
future might allow the treatment of this syndrome
to be customized.

Acknowledgements
The authors would like to thank Dr Francesca Lazzarotto
and Dr Francesca Barbon for their contribution to the case

96

studies evaluation and Ms Catherine Crowley for editorial
assistance.

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Component-resolved diagnosis with recombinant
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Immunol 2002;110:167–73.
9. Mari A, Ballmer-Weber BK, Vieths S. The oral allergy
syndrome: improved diagnostic and treatment
methods. Curr Opin Allergy Clin Immunol
2005;5:267–73.
10. Asero R. Plant food allergies: A suggested approach to
allergen-resolved diagnosis in the clinical practice by
identifying easily available sensitization markers. Int
Arch Allergy Immunol 2005;138:1–11.
11. Sampson HA, Muñoz-Furlong A, Campbell RL, et al.
Second symposium on the definition and management
of anaphylaxis: summary report – Second National
Institute of Allergy and Infectious Disease/Food Allergy
and Anaphylaxis Network symposium. J Allergy Clin
Immunol 2006;117:391–7.
12. Ballmer-Weber BK, Wüthrich B, Wangorsch A, et al.
Carrot allergy: double-blind placebo-controlled food
challenge and identification of allergens. J Allergy Clin
Immunol 2001;108:310–7.
13. Kleine-Tebbe J, Vogel L, Crowell DN, et al. Severe oral
allergy syndrome and anaphylactic reactions caused by
a Bet v 1-related PR-10 protein in soybean, SAM22. J
Allergy Clin Immunol 2002;110:797–804.
14. Magnusson J, Lin XP, Dahlman-Höglund A, et al.
Seasonal intestinal inflammation in patients with

Pollen–Food Syndrome
birch pollen allergy. J Allergy Clin Immunol 2003;112:
45–50.
15. Breiteneder H, Ebner C. Molecular and biochemical
classification of plant derived food allergens. J Allergy
Clin Immunol 2000;106:27–36.
16. van Ree R. Clinical importance of cross-reactivity in
food allergy. Curr Opin Allergy Clin Immunol
2004;4:235–40.
17. Sánchez-Monge R, Lombardero M, García-Sellés FJ,
et al. Lipid-transfer proteins are relevant allergens
in fruit allergy. J Allergy Clin Immunol 1999;103:
514–51.
18. Désormeaux A, Blochet JE, Pézolet M, et al. Amino
acid sequence of a non-specific wheat phospholipid
transfer protein and its conformation as revealed by
infrared and Raman spectroscopy: role of disulfide
bridges and phospholipids in the stabilization of the
α-helix structure. Biochim Biophys Acta
1992;1121:137–52.
19. Van Ree R. Clinical importance of nonspecific lipid
transfer proteins as food allergens. Biochem Soc Trans
2002;30:910–3.
20. Lleonart R, Cistero A, Carreira J, et al. Food Allergy:
Identification of the major IgE-binding component of
peach. Ann Allergy 1992;69:128–30.
21. Asero R, Mistrello G, Roncarolo D, et al.
Immunological cross-reactivity between lipid
transfer proteins from botanically unrelated plantderived foods: a clinical study. Allergy 2002;57:
900–6.
22. Asero R, Mistrello G, Roncarolo D, et al. Relationship
between peach lipid transfer protein IgE levels and
hypersensitivity to non-Rosaceae vegetable foods in
patients allergic to lipid transfer protein. Ann Allergy
Asthma Immunol 2004;92:268–72.
23. Pastorello EA, Ortolani C, Farioli L, et al. Allergenic
cross-reactivity among peach, apricot, plum, cherry in
patients with oral allergy syndrome. An in vivo and
in vitro study. J Allergy Clin Immunol 1994;94:
699–707.
24. Lombardero M, Garcia-Selles FJ, Polo F, et al.
Prevalence of sensitization to Artemisia allergens Art v
1, Art v 3 and Art v 60 kDa. Cross-reactivity among Art
v 3 and other relevant lipid-transfer protein allergens.
Clin Exp Allergy 2004;34:1415–21.
25. Rohrer CL, Pichler WJ, Helbling A. Anaphylaxis:
clinical aspects, etiology and course in 118 patients.
Schweiz Med Wochenschr 1998;128:53–63.
26. Mittag D, Vieths S, Vogel L, et al. Soybean allergy
in patients allergic to birch pollen: clinical
investigation and molecular characterization of
allergens. J Allergy Clin Immunol 2004;113:
148–54.
27. Van Ree R, Voitenko V, van Leeuwen WA, et al.
Profilin is a cross-reactive allergen in pollen and
vegetable foods. Int Arch Allergy Immunol 1992;98:
97–104.
28. Asero R, Monsalve R, Barber D. Profilin sensitization
detected in the office by skin prick test: a study of
prevalence and clinical relevance of profilin as a

7

plant food allergen. Clin Exp Allergy 2008;38:
1033–7.
29. Foetisch K, Westphal S, Lauer I, et al. Biological activity
of IgE specific for cross-reactive carbohydrate
determinants. J Allergy Clin Immunol 2003;111:
889–96.
30. Bohle B, Vieths S. Improving diagnostic tests for food
allergy with recombinant allergens. Methods
2004;32:292–9.
31. Vieths S, Jankiewicz A, Schoning B, et al. Apple allergy:
the IgE-binding potency of apple strains is related to
the occurrence of the 18-kDa allergen. Allergy
1994;49:262–71.
32. Hoffmann-Sommergruber K, Demoly P, Crameri R,
et al. IgE reactivity to Api g 1, a major celery allergen,
in a Central European population is based on primary
sensitization by Bet v 1. J. Allergy Clin Immunol
1999;104:478–84.
33. Vieths S, Scheurer S, Reindl J, et al. Optimized
allergen extracts and recombinant allergens in
diagnostic applications. Allergy 2001;56(Suppl 67):
78–82.
34. Luttkopf D, Muller U, Skov PS, et al. Comparison
of four variants of a major allergen in hazelnut
(Corylus avellana) Cor a 1.04 with the major hazel
pollen allergen Cor a 1.01. Mol Immunol 2002;38:
515–25.
35. Ballmer-Weber BK, Wangorsch A, Bohle B, et al.
Component-resolved in vitro diagnosis in carrot
allergy: does the use of recombinant carrot allergens
improve the reliability of the diagnostic procedure?
Clin Exp Allergy 2005;35:970–8.
36. Bolhaar S, van Ree R, Ma Y, et al. Severe allergy to
Sharon fruit caused by birch pollen. Int Arch Allergy
Immunol 2005;136:45–52.
37. Erdmann SM, Sachs B, Schmidt A, et al. In vitro
analysis of birch-pollen associated food allergy by use
of recombinant allergens in the basophil activation
test. Int Arch Allergy Immunol 2005;136:230–8.
38. Ma S, Sicherer S, Nowak-Wegrzyn A. A survey on the
management of pollen–food allergy syndrome in
allergy practices. J Allergy Clin Immunol
2003;112:784–8.
39. Rodriguez J, Crespo JF, Lopez-Rubio A. Clinical
crossreactivity among foods of the Rosaceae family.
J Allergy Clin Immunol 2000;106:183–9.
40. Bohle B. The impact of pollen-related food allergens
on pollen allergy. Allergy 2007;62:3–10.
41. Bohle B, Zwolfer B, Heratizadeh A. Cooking birch
pollen-related food: divergent consequences for
IgE- and T cell-mediated reactivity in vitro and in vivo.
J Allergy Clin Immunol 2006;118:242–9.
42. Asero R. Effects of birch pollen-specific immunotherapy
on apple allergy in birch pollen-hypersensitive patients.
Clin Exp Allergy 1998;28:1368– 73.
43. Buchner X, Pichler WJ, Dahinden CA, et al. Effect of
tree pollen specific, subcutaneous immunotherapy on
the oral allergy syndrome to apple and hazelnut.
Allergy 2004;59:1272–6.

97

Food Allergy
44. Moller C. Effect of pollen immunotherapy on food
hypersensitivity in children with birch pollinosis. Ann
Allergy 1989;62:343–5.
45. Modrzynski M, Zawisza E. Possible induction of oral
allergy syndrome during specific immunotherapy in
patients sensitive to tree pollen. Med Sci Monit
2005;11:CR351–5.

98

46. Kinaciyan T, Jahn-Schmid B, Radakovics A, et al.
Successful sublingual immunotherapy with birch
pollen has limited effects on concomitant food allergy
to apple and the immune response to the Bet v 1
homolog Mal d 1. J Allergy Clin Immunol
2007;119:937–43.

CHAPTER

8 

The Respiratory Tract and Food Allergy
John M. James

Introduction
CLINICAL CASE
A 15-month-old boy presents to your clinic with a history
of atopic dermatitis and allergy to cows’ milk. Previous
reactions following the ingestion of cows’ milk have
provoked exacerbations of eczema and urticaria. Following
a recent accidental ingestion of cows’ milk, when the infant
was given a sibling’s cup of cows’ milk instead of soy milk,
he experienced immediate generalized urticaria, emesis,
coughing and significant wheezing requiring management
in a local emergency department. Medical therapies
included one dose of intramuscular epinephrine, oral
antihistamines every 4 hours (i.e. three doses), nebulized
albuterol and two doses of systemic corticosteroids 12
hours apart. The infant was observed in the hospital for 24
hours and then discharged home in good condition.

This clinical case provides a good introduction to
respiratory manifestations of food allergy. Skin and
gastrointestinal tract symptoms are commonly
observed with allergic reactions to foods, but respiratory tract symptoms may also be involved, as
illustrated above.1–3 Specific respiratory symptoms
that can be observed include nasal congestion, rhinorrhea, sneezing, pruritus of the nose and throat,
coughing, wheezing and asthma. Anaphylactic reactions can also occur. Exposure is typically through
ingestion, but in some cases inhalation of food
allergens may also precipitate these reactions.4 In
fact, an increasing number of medical publications
have highlighted allergic reactions to food allergens
that have occurred following inhalation. Food
allergy in early childhood does appear to be a
© 2012, Elsevier Inc

good marker for later respiratory allergy, including
asthma. In addition, studies have demonstrated
that food-induced allergic reactions can provoke
recurrent asthmatic responses, as well as persistent
asthma. Food allergy can also increase asthma morbidity in adults and children,5 therefore, evaluation
for food allergy should be considered in patients
with difficult to control or otherwise unexplained
acute severe asthma exacerbations and in patients
with asthma and other manifestations of food
allergy (e.g. anaphylaxis, moderate to severe atopic
dermatitis). As highlighted in the clinical case
above, anaphylactic reactions to foods in children
almost always include respiratory tract symptoms,
and these often determine the severity and outcome
of the reaction. This highlights the importance of
documenting respiratory tract symptoms as part of
a food allergic reaction (Clinical Pearl 1)
CLINICAL PEARL #1

FOOD ALLERGY/RESPIRATORY TRACT/
ANAPHYLAXIS
General Caveats
• Exposure through ingestion of food allergen(s)
provokes most reactions
• Inhalation of food allergen(s) can lead to respiratory
symptoms
• Consider food allergy evaluation in patients with chronic
asthma and unexplained, acute asthma exacerbations
• Anaphylaxis almost always involves the respiratory tract
• Respiratory manifestations of food-induced anaphylaxis
often determine severity and outcome of reaction

Food Allergy

Epidemiology
Overview
Adverse reactions to foods can commonly provoke
clinical signs and symptoms involving the skin, the
gastrointestinal tract, the respiratory tract, and in
some cases the cardiovascular system. These reactions consist of any abnormal clinical responses
following the ingestion of a food or food additive,
and can be further divided into two major cate­
gories.1 The vast majority can be categorized as
adverse physiologic reactions or food intolerances,
which are not mediated by specific immunologic
mechanisms (e.g. an exaggerated physiological
reaction following the ingestion of lactose in
cows’ milk causing abdominal distension, gas
and diarrhea). In contrast, food allergy is an
immunologic-mediated food reaction unrelated to
any physiologic effect of the food or additive. The
two broad groups of immune reactions are IgE
mediated and non-IgE mediated. The IgE-mediated
reactions are usually divided into immediate-onset
and immediate plus late-phase reactions, which
involve an immediate onset of symptoms followed
by prolonged or ongoing symptoms. Typical examples of immediate-onset IgE-mediated reactions
include allergic reactions following the ingestion
of peanuts, tree nuts, shellfish or sesame seeds
resulting in laryngeal edema, coughing and/or
wheezing. Non-IgE-mediated reactions are typically
delayed in onset (i.e. 4–48 hours) and most frequently involve the gastrointestinal tract (e.g. celiac
disease or gluten-sensitive enteropathy). It is imperative to understand the specific terminology and
basic classification of adverse food reactions to
properly interpret the scientific studies implicating
food allergy in respiratory tract symptoms and
anaphylaxis.

Prevalence
Over the past 20 years there has been an increase
in the prevalence of food allergy and its clinical
expression.1,6 The exact prevalence of respiratory
tract symptoms induced by food allergy, however,
has been difficult to establish. For many years there
has been a public perception that food allergyinduced asthma is common, but this has not been
substantiated when careful objective investigations,
including food challenges, have been undertaken to

100

confirm patient histories.7,8 When the specific focus
has been on the role of food allergy and respiratory
tract manifestations, the incidence has been estimated to be between 2% and 8% in children and
adults with asthma.5,9,10 Using a cross-sectional epidemiologic study design in 1141 randomly selected
young adults ranging in age from 20 to 45 years,
Australian investigators evaluated the prevalence of
IgE-mediated food allergy and the relationships
with other atopic disease.11 Those with probable
IgE-mediated peanut allergy were more likely to
have current asthma, wheeze and a history of
eczema, and those with probable IgE-mediated
shrimp allergy were also more likely to have current
asthma and nasal allergies. No relationships were
observed between those subjects with probable IgEmediated cows’ milk, wheat and egg allergy and
allergic diseases because of small numbers of subjects with these food allergies. They concluded that
further research, with larger numbers of subjects
demonstrating IgE-mediated food allergy, would be
required to confirm these results.
To examine the strength of the association and
temporal relationships between food allergy and
asthma, investigators followed 271 children over 6
years of age and 296 children less than 6 years from
a family-based food allergy cohort in Chicago.12
Food allergy status was determined based on the
type and timing of clinical symptoms after ingestion of a specific food and results of specific IgE to
foods using skin prick testing and allergen-specific
IgE. Symptomatic food allergy was associated with
asthma in both older (odds ratio (OR) = 4.9, 95%
confidence interval (CI): 2.5–9.5) and younger children (OR = 5.3, 95% CI: 1.7–16.2). The association
was stronger among children with multiple or
severe food allergies, especially in older children.
Children with food allergy developed asthma
earlier and at a higher prevalence than children
without food allergy. No associations were seen
between asymptomatic food sensitization and
asthma. Independent of markers of atopy (e.g. aeroallergen sensitization and family history of
asthma), there was a significant association between
food allergy and asthma.
To determine the prevalence, clinical features,
specific allergens and risk factors of food allergy, a
population study including 33 110 persons completing a questionnaire was conducted in France.13
The overall prevalence of food allergy was estimated
to be 3.24%, with rhinitis and asthma documented

The Respiratory Tract and Food Allergy

in 6.5% and 5.7% of respiratory reactions, respectively. In addition, the clinical expression of food
allergy was dependent on the existence of sensitization to pollens and was typically expressed in the
form of rhinitis, asthma and angioedema. Another
survey found that 17% of 669 adult respondents in
Australia reported food-induced respiratory symptoms.14 Whereas the patients with asthma did not
report food-related illness more frequently than
those without asthma, those reporting respiratory
symptoms following food ingestion were more
likely to be atopic.

CLINICAL CASE
A family presents to your clinic with a 10-month-old girl
who has a clinical history and course very compatible with
allergy to egg protein. Following the ingestion of
scrambled eggs on two prior occasions, the infant has had
emesis and urticaria without anaphylactic manifestations.
The infant is otherwise healthy and does not have atopic
dermatitis or other atopic conditions. Both parents have a
history of allergic rhinitis. The parents specifically ask
about the likelihood of their infant developing allergic
respiratory diseases such as asthma and allergic rhinitis
later in childhood. This clinical case illustrates a very
important point that children with a family history of
atopy and sensitization to food proteins in early infancy
may have a higher risk of developing subsequent
respiratory allergic disease.15 Investigators from the Isle of
Wight reported that egg allergy in infancy predicts
respiratory allergic disease by 4 years of age.16 In a cohort
of 1218 consecutive births followed until 4 years of age, 29
(2.4%) developed egg allergy by 4 years of age. Increased
respiratory allergy (e.g. rhinitis, asthma) was associated
with egg allergy (OR: 5.0, 95% CI: 1.1–22.3; p < 0.05) with a
positive predictive value of 55%. Furthermore, the addition
of the diagnosis of eczema to egg allergy increased the
positive predictive value to 80%. Rhodes et al.17 conducted
a prospective cohort study of subjects at risk of asthma
and atopy in England. Of 100 babies of atopic parents who
were recruited at birth, 73 were followed up at 5 years, 67
at 11 and 63 at 22 years of age. Skin sensitivity to hen’s
egg, cows’ milk or both in the first 5 years of life was
predictive of asthma (OR: 10.7; 95% CI: 2.1–55.1; p = 0.001,
sensitivity 57%; specificity 89%).

One specific focus area of the National Cooperative
Inner City Asthma Study examined the degree of
food allergen sensitization to six common foods
(egg, milk, soy, peanut, wheat and fish) in 504
inner-city patients 4–9 years of age (median 6 years)
with asthma.18 Children sensitized to foods had
higher rates of asthma hospitalization (p <0.01) and
required more steroid medications (p = 0.25). In
addition, sensitization to foods was correlated with

8

sensitization to more indoor and outdoor aeroallergens (p < 0.001). The association of increased
asthma morbidity with at least one food sensitization and findings that patients with sensitization
to multiple foods had significantly more asthma
morbidity than those with single-food sensitization
suggests that food allergen sensitivity may be a
marker for increased asthma severity.
An investigation by Sicherer and colleagues19
summarized data from a voluntary registry of 5149
individuals (median age 5 years) with peanut and/
or tree nut allergy. The primary objective was to
characterize clinical features including respiratory
reactions in the registrants. Respiratory reactions,
including wheezing, throat tightness and nasal congestion, were reported in 42% and 56% of respondents as part of their initial reactions to peanuts and
tree nuts, respectively. One half of the reactions
involved more than one system and more than 75%
required some form of medical treatment. Interestingly, registrants with asthma were significantly
more likely than those without asthma to have
severe reactions (33% versus 21%; p < 0.0001).
Moreover, another investigation by the same group
estimated the prevalence of seafood allergy in the
United States using a nationwide, cross-sectional
random telephone survey and standardized questionnaire. A total of 5529 households completed
the survey, representing a census of 14 948 individuals. Fish or shellfish allergy was reported in
5.9% of households. Recurrent reactions were
common. Shortness of breath and throat tightness
was reported by more than 50% of those surveyed
and 16% were treated with epinephrine20 (Clinical
Pearl 2).
CLINICAL PEARL #2

ROLE OF FOOD ALLERGY IN RESPIRATORY
MANIFESTATIONS
Epidemiology
• Incidence estimated at approximately 2–8% of patients
with asthma
• Pollen sensitization may be an associated risk factor
• Family history of atopy and sensitization to food
allergens in early infancy increase the risk of future
allergic respiratory disease (e.g. asthma, allergic
rhinitis)
• Allergic sensitization to some foods may be a marker
for increased asthma severity

101

Food Allergy

Pathogenesis
Mechanisms
Our understanding of how food allergy causes a
significant disruption of normal oral tolerance continues to evolve. Recently, it has become evident
that the gut, which is the classic site of sensitization
to foods, is only responsible for primary sensitization in a subset of patients. These patients are generally younger and exhibit their first symptoms
shortly after initial exposures to the relevant food.
In contrast, a newly recognized route of sensitization for food-allergic patients is by initial exposure
to allergens through inhalation, mostly pollens,
with secondary clinical reactions following ingestion of specific cross-reactive foods. In these
patients, many years may elapse before the first
respiratory symptoms appear. Investigations from
Europe suggest that lipid transfer proteins (LTP)
may induce significant allergic sensitization through
the respiratory tract due to inhalation, and this may
precede the onset of relevant food allergy.21,22 For
example, inhalation of LTP from specific fruits (e.g.
peaches and apples) may lead to allergic sensitization and ultimately allergic reactions following the
oral ingestion of these foods.

Allergens
Specific foods are more often implicated in food
allergic reactions involving respiratory symptoms
and have subsequently been confirmed in wellcontrolled, blinded food challenges.7,23,24 These
foods include chicken egg, cows’ milk, peanut, fish,
shellfish and tree nuts (Clinical Pearl 3). For
example, one group of young children who were
allergic to cows’ milk was followed from 1 year of
age until 5 years.25 These patients did develop early
respiratory symptoms, including nasal symptoms
and cough, without skin or gastrointestinal symptoms, and 69% did ultimately develop allergic
sensitivities to common indoor aeroallergens. In
addition, anaphylactic reactions to foods, including
significant respiratory symptoms, and rarely fatal
anaphylactic reactions have been reported.26–29
Some food allergens seem to be more prone to
present with respiratory tract symptoms, such as
peanuts and tree nuts,19 fish and shellfish20 or
sesame.30 Finally, there have been many food allergens implicated as the cause of respiratory tract
allergy symptoms following inhalation as opposed
102

CLINICAL PEARL #3

COMMON FOOD ALLERGENS HAVE BEEN
IMPLICATED IN RESPIRATORY DISEASE
• Chicken egg, cows’ milk, peanut, fish, shellfish and tree
nuts have been the main foods responsible for food
allergen-induced respiratory reactions
• Peanuts, tree nuts, sesame seed and shellfish have
most often been responsible for near-fatal and fatal
anaphylactic reactions following food ingestion

to ingestion.4 Common examples include fish,
shellfish and eggs.31
Baker’s asthma is among one of the most common
occupational diseases and results from inhalation
of relevant wheat allergens. Thus far, however, little
is known about those allergens. Only a few of the
suspected causative wheat allergens have been characterized on the molecular level. The aim of a recent
investigation in Germany was to identify and characterize unknown wheat allergens related to baker’s
asthma to improve the reliability of diagnostic procedures.32 Of the asthmatic bakers studied, 33%
showed sensitization to native total gliadin. Gliadins represent a newly discovered family of inhaled
allergens in baker’s asthma and these water-insoluble
proteins might represent causative allergens. The
presence of asthma induced by inhaled flour is not
strictly related to occupational exposure and may
also occur in subjects not displaying asthma among
symptoms induced by wheat ingestion.33
A high percentage of patients with asthma perceive that food additives contribute to worsening
of their respiratory symptoms.34 Several different
food additives, including monosodium glutamate,
sulfites and aspartame, have been implicated in
adverse respiratory reactions,35 but well-controlled
investigations in this area have reported a prevalence rate of < 5%.9,23 Food additives as a trigger for
asthma have been a controversial area, with few
data to support a cause and effect,36 and studies
have shown the prevalence to be much less than
1% of the total population. There are more than
2500 food additives, but only a few are known to
be triggers of asthma. Sulfites and monosodium
glutamate (MSG) are the most often implicated and
the most studied. Sulfites are used as a preservative
and found in many foods, including dried fruits,
wine, sauerkraut, white grape juice, dried potatoes
and fresh shrimp. Overall, the prevalence of sulfiteinduced asthma responses appears to be < 3.9%.

The Respiratory Tract and Food Allergy

Monosodium glutamate (MSG) is the flavor
enhancer that has been held responsible for the
‘Chinese restaurant syndrome’, which is clinically
manifested by headache, numbness, chest discomfort, weakness, flushing and abdominal discomfort
after eating Chinese food. Focusing on conflicting
evidence that some people with asthma are more
likely to have adverse effects from monosodium
glutamate than the general population, Woods
and co-workers37 were unable to demonstrate MSGinduced immediate or late asthmatic reactions in
12 adult asthmatics reporting food additive-induced
symptoms. In addition, no significant changes in
bronchial hyperresponsiveness or soluble inflammatory markers (e.g. eosinophil cationic protein,
tryptase) were observed during these challenges. In
an investigation utilizing double-blind placebocontrolled oral MSG challenges in subjects who had
histories of adverse reactions to MSG,38 no specific
upper or lower respiratory complaints were
observed, but 22 (36.1%) of the 61 subjects had
confirmed adverse reactions to MSG including
headache, muscle tightness, numbness, general
weakness and flushing.

Route of exposure and subsequent
respiratory symptoms
Oral ingestion of food allergens
Oral ingestion is the primary route of exposure to
foods that can cause or exacerbate respiratory symptoms (e.g. cough, laryngeal edema and asthma).
The vast majority of published reports, highlighted
in this chapter, focus on respiratory tract symptoms
following the ingestion of food allergens.

Inhalation of food allergens
CLINICAL CASE
A 33-year-old man was evaluated at his family physician’s
office for a recent adverse food reaction. He was at a
shopping mall and stopped to have lunch in a designated
food court area. There were several different types of food
being served, including pizza, Chinese food, fried shrimp
and sushi, and there was a strong aroma of all of these
foods in the court. He had a past history of anaphylactic
reactions following the ingestion of shrimp. While he was
eating a salad without any seafood, he noticed itching in
his mouth and throat, a swelling sensation in his throat
and repetitive coughing. If this patient did not ingest any
shrimp, could this still represent an allergic reaction to
shrimp?

8

This clinical case is an example of how some foodallergic individuals may react when exposed to airborne allergens in a restaurant when fish or shellfish
are cooked in a confined area.31,39 Seafood allergens
aerosolized during food preparation are a source
of potential respiratory and contact allergens.40 A
number of reports highlight allergic reactions associated with airborne fish particles,41,42 including one
using air sampling and an immunochemical analytic technique to detect fish allergen in the air of
an open-air fish market.43 Avoidance of a food allergen should include the prevention of exposure to
aerosolized particles in relevant environments.
Finally, an internet-based survey of 51 anaphylactic
reactions to foods showed that whereas most reactions (40–78%) occurred after ingestion, eight
(16%) reactions occurred following exclusive skin
contact and three (6%) after inhalation.44
Children with IgE-mediated food allergy can
develop asthma following inhalational exposure to
aerosolized food allergens during the cooking
process.45 Twelve food-allergic children developed
asthma following the inhalation of relevant food
allergens. Foods implicated included fish, chickpea,
milk, egg and buckwheat. Five of nine bronchial
challenges were positive with objective clinical features of asthma, and two children developed latephase symptoms with a decrease in lung function.
Positive reactions were seen with fish, chickpea and
buckwheat; there were no reactions to the seven
placebo challenges. These data demonstrate that
inhaled food allergens can produce both early- and
late-phase asthmatic responses. Finally, Sicherer
and colleagues46 have reported that patients with
allergy to peanuts and tree nuts might experience
adverse respiratory reactions when they are exposed
on airline flights serving peanut and tree nut snacks.
Such exposures can include accidental ingestion,
inhalation or skin contact during the flight. Of the
allergic reactions reported, some were severe, requiring medications including epinephrine.

Differential diagnosis of
food-induced respiratory
syndromes (Table 8.1)
Many questions remain when evaluating respiratory manifestations that may be a clinical manifestation of food allergy. Unlike cutaneous symptoms
(e.g. urticaria, angioedema), respiratory manifestations may be immediate, delayed or chronic, mostly
103

Food Allergy
Table 8.1  Differential Diagnosis of Food-Induced
Respiratory Syndromes
1.  Eczema within the first 2 years of life and risk of
developing asthma and allergic rhinitis
2. Food allergy in infancy and risk for wheezing and
hyperactive airways in childhood
3. Acute asthma induced by food allergy
4. Respiratory symptoms contributing to the severity of
acute allergic reactions to foods
5. Patients with recurrent or chronic asthma
6. Food allergy and predisposition to bronchial
hyperreactivity (BHR)
7. Recurrent or chronic rhinitis induced by food allergy
8. Recurrent or chronic otitis media induced by food allergy
9. Dyspnea associated with anemia in infants

due to the pattern of inflammatory manifestations
of the respiratory tract. This section will review
potential manifestations of food allergy in the respiratory tract.

Recurrent or chronic rhinitis induced by
food allergy
In a large group of children undergoing doubleblind placebo-controlled food challenges47 acute
rhinitis accounted for 70% of the overall respiratory
symptoms observed. These symptoms typically
occur in association with other clinical manifestations (e.g. cutaneous and/or gastrointestinal symptoms) during allergic reactions to foods; they rarely
occur in isolation.23,47 Chronic or recurrent rhinitis,
mostly in preschool children, is sometimes associated with allergic reactions, mostly to milk.
Although some patients claim of a significant
decrease in symptoms after starting an avoidance
diet, a clear association has not been reproduced by
double-blind studies.

Recurrent or chronic otitis media
induced by food allergy
Serous otitis media has multiple etiologies, viral
upper respiratory tract infections being the most
common. Allergic inflammation in the nasal
mucosa may cause eustachian tube dysfunction
and contribute to subsequent otitis media with
effusion. Studies investigating a food-allergic
mechanism in recurrent serous otitis media are
inconclusive.48,49
104

Dyspnea associated with anemia
in infants
In 1960, Heiner50 reported a syndrome in infants
consisting of recurrent episodes of pneumonia
associated with pulmonary infiltrates, hemosiderosis, gastrointestinal blood loss, iron-deficiency
anemia and failure to thrive. This syndrome is most
often associated with a non-IgE-mediated hypersensitivity to cows’ milk proteins. Although
increased peripheral blood eosinophils and multiple serum precipitins to cows’ milk are commonly
observed, the specific immunologic mechanisms
responsible for this disorder are not known.51 The
diagnosis is suggested by infiltrates on chest X-ray,
anemia, hemosiderosis evidenced by bronchoalveolar lavage and the presence of the precipitating
antibodies to milk (in most cases). This foodinduced syndrome is only very rarely observed even
in referral clinics for childhood food allergy.

Eczema within the first 2 years of life
and risk of developing asthma and
allergic rhinitis
The presence of persistent eczema in infancy has
been identified as an important risk factor for the
development of allergic rhinitis and asthma. In one
study,52 children with atopic eczema had a significantly greater risk of asthma (OR = 3.52, 95% CI =
1.88–6.59 and allergic rhinitis OR = 2.91, 95%CI =
1.48–5.71). This risk was not observed in the
control patients.
Although a family history of atopy, including the
presence of atopic dermatitis and food allergy,
appears to contribute to the development of asthma,
it is unclear when the airways become involved
with the atopic process and whether airway function relates to the atopic characteristics of the
infant. In one study of 114 infants (median age 10.7
months; range 2.6–19.1), atopic status was determined by the presence of specific IgE to foods or
aeroallergens and total IgE levels.53 Exhaled nitric
oxide (eNO), forced expiratory flow at 75% exhaled
volume (FEF75) and airway reactivity to inhaled
methacholine were measured in these infants.
Compared to non-atopic controls, infants sensitized to egg or milk had lower flow rates (FEF75:
336 vs 285 mL/s, p < 0.003) and lower InPC(30)
(mg/mL) provocative concentrations to decrease
FEF(75) by 30% (−0.6 vs −1.2, p < 0.02) but no
difference in eNO levels. This suggests that atopic

The Respiratory Tract and Food Allergy

characteristics of the infant might be important
determinants for the development of asthma.

Food allergy in infancy and risk for
wheezing and hyperactive airways
in childhood
Children allergic to common food allergens in
infancy may be at increased risk of wheezing
and bronchial hyperreactivity later in childhood. A
case–control study was conducted with 69 children
aged 7.2–13.3 years with allergy to egg (n = 60)
and/or fish (n = 29) in the first 3 years of life.54 A
control group consisted of 154 children (70 sensitized to inhaled allergens) with no history of food
allergy in the first 3 years of life. Asthma symptoms
were reported more frequently in the study group
than in controls. Children in the study group
showed a significantly increased frequency of positive responses to methacholine challenge than the
control group. Multivariate logistic regression analysis showed that bronchial hyperresponsiveness, as
well as reported current asthma symptoms, was
associated with early wheezing and early sensitization to inhaled allergens but not with atopic dermatitis in infancy or persistence of egg or fish
allergy. Therefore, children allergic to egg or fish in
infancy may be at increased risk for wheezing illness
and hyperactive airways in the school years.

Acute asthma induced by food allergy
CLINICAL CASE
A very frustrated young couple decides to seek the
opinion of an allergy specialist regarding their 3-year old
daughter. She has a long-standing history of eczema and
has recently been diagnosed with asthma. Her parents
believe that some of her acute exacerbations of asthma
may have been provoked by the accidental ingestion of
cows’ milk protein. Their primary care physician informed
them that this is not very likely because asthma
exacerbations in this age group are typically caused by
viral upper respiratory infections. They are seeking an
expert opinion about the role of food allergy in acute
asthma.

The wide use of standardized food challenges has
provided a better view of the type and frequency of
respiratory reactions in food allergy. Hill and colleagues55 challenged 100 milk-allergic patients with
a mean age of 16.2 months and elicited cough and/
or wheeze in 20, rhinitis in 12 and stridor in two.
Cough and wheezing were more frequent in the

8

patients who initially presented with chronic
eczema and recurrent bronchitis, and with urticaria
and eczema. Lower respiratory symptoms were only
observed in two of 53 patients (4%). In another
study of 410 children with a history of asthma, 279
(68%) had a history of food-induced asthma.56
There were positive food challenges in 168 (60%)
of the 279 patients. This investigation documented
that 67 (24%) of the 279 children with a history
of food-induced asthma had a positive blinded
food challenge that included wheezing. The most
common foods responsible for these reactions
included peanut (19), cows’ milk (18), egg (13)
and tree nuts (10). Interestingly, only five (2%) of
these patients had wheezing as their only objective
adverse symptom. In addition, 10 of the group of
188 children without a history of asthma had
wheezing elicited by the food challenge, showing a
tendency for a bronchial response in the absence of
a concomitant asthma.
A total of 320 subjects presenting primarily with
atopic dermatitis undergoing blinded food challenges were monitored for respiratory reactions.47
The subjects, aged between 6 months and 30 years,
were highly atopic and had multiple allergic sensitivities to foods, and over half had a prior diagnosis
of asthma. In the 205 (64%) patients with food
allergy confirmed by blinded challenges, almost
two-thirds experienced respiratory reactions during
their positive food challenges (e.g. nasal 70%,
laryngeal 48%, pulmonary 27%). Overall, 34
(17%) of 205 subjects with positive food challenges
developed wheezing as part of their reaction. Furthermore, 88 of these patients were monitored with
pulmonary function testing during positive and
negative food challenges. Thirteen (15%) developed lower respiratory symptoms, including wheezing in 10, but only six had a > 20% decrease in FEV1.
Wheezing as the sole manifestation of a foodinduced respiratory reaction was rare.
In a series of 163 children in which 385 DBPCFC
were performed,57 250 challenges (65%) were positive to peanuts (31%), hens’ egg (23%) and cows’
milk (9%). Cutaneous symptoms were observed in
most positive challenges (59%), but respiratory
reactions were also frequent (24%). Among the respiratory reactions, oral symptoms (5%), rhinitis
and conjunctivitis (6%) and asthma (10%) were
observed. Again, isolated asthma was rare, i.e. 2.8%
of the challenges. Furthermore, investigations from
Italy suggest that asthma and/or rhinitis as part
of the initial presentation of allergy to cows’ milk
105

Food Allergy

may be an independent predictor of persistence
of this food allergy and a failure to develop oral
tolerance.58

Food allergy and predisposition to
bronchial hyperreactivity (BHR)
Observations have been made that asthma symptoms have improved in patients with atopic dermatitis and food allergy who are following a food
avoidance diet, despite the absence of respiratory
symptoms during specific food challenges. This
prompted a series of investigations on bronchial
hyperreactivity (BHR) in food-allergic patients
without acute respiratory symptoms following food
ingestion. In one investigation, 26 children with
asthma and food allergy were evaluated using
methacholine inhalation challenges for changes in
their BHR before and after blinded food challenges.59 Of the 22 positive blinded food challenges,
12 (55%) involved chest symptoms (cough, laryngeal reactions and/or wheezing). Another 10 (45%)
positive food challenges included laryngeal, gastrointestinal and/or skin symptoms without any
chest symptoms. Significant increases in BHR were
documented several hours after positive food challenges in seven of the 12 (58%) patients who experienced chest symptoms during these challenges.
During the actual food challenges decreases in FEV1
were not observed in these seven patients, suggesting that significant changes in BHR can occur
without significant pulmonary function changes in
a preceding food challenge. These data confirmed
that food-induced allergic reactions may increase
airway reactivity in a subset of patients with moderate to severe asthma, and may do so without inducing acute asthma symptoms.
A more recent investigation hypothesized that
children allergic to common food allergens in
infancy are at increased risk of wheezing illness and
bronchial hyperresponsiveness during the school
years.60 A case–control study of 69 children aged
7.2 to 13.3 years allergic to egg (n = 60) and/or fish
(n = 29) in early life (first 3 years) was conducted.
The children received follow-up for 1 year and were
evaluated by parental questionnaire, skin prick
testing, spirometry and metacholine bronchial
challenge. A control group consisted of 154 children (70 sensitized to inhaled allergens) from a
general population sample with no history of food
allergy during their first 3 years. Food-allergic
patients showed a significantly increased frequency
106

of positive response to metacholine bronchial challenge compared to the control group as a whole.
Children allergic to egg or fish in infancy are at
increased risk for wheezing illness and hyperactive
airways at school age; asthma and bronchial hyperresponsiveness seem to be mostly determined by
wheezing and sensitization to inhaled allergens in
early life, regardless of atopic dermatitis in infancy
or retention of food allergy.
In contrast, another study of 11 adult asthmatics
with a history of food-induced wheezing and positive skin tests to the suspected food concluded that
food allergy is an unlikely cause of increased BHR.61
An equal number of patients had increased BHR,
as determined by methacholine inhalation challenges, 24 hours after blinded food challenges to
either food allergen or placebo. However, the small
number of patients evaluated and the lack of environmental controls prior to the repeat methacholine challenges limit their conclusions.
Two more recent studies indicate that patients
with food allergy in the absence of asthma might
develop increased BHR. In 35 non-asthmatic
patients with food allergy, 10 of 19 (53%) were
found to have BHR by methacholine inhalation
challenges.62 Similarly, Kivity et al. 63 investigated
patients with food allergy with or without asthma
and/or allergic rhinitis by spirometry, methacholine
challenges and sputum-induced cell analysis. BHR
by methacholine challenge was observed in all
patients with asthma, and in 40% of patients with
food allergy alone. They also found mainly eosinophils in the sputum of patients with asthma, and
neutrophils in the patients with food allergy but no
asthma. This observation has been confirmed by
other investigators, who also observed an increased
proportion of neutrophils and increased levels of
IL-8 in non-asthmatic food-allergic patients.64
An animal study came to a similar conclusion,
as mice sensitized by intraperitoneal injection of
ovalbumin in the presence of alum and orally
challenged to ovalbumin had significant airway
inflammation for up to 12 days following a single
intranasal challenge to ovalbumin.65 Interestingly,
an unrelated antigen, house dust mite, did induce
a similar inflammatory response. Taken together,
these observations suggest that food sensitization
with non-respiratory manifestations of food allergy
may also enhance inflammation in other mucosal
tissues. Hence, non-asthmatic patients diagnosed
with food allergy should be carefully evaluated
for bronchial inflammation in order not to

The Respiratory Tract and Food Allergy

delay appropriate anti-inflammatory treatment if
necessary.

Respiratory symptoms contributing to
the severity of acute allergic reactions
to foods
CLINICAL CASE
A 17-year-old male college student experienced a severe
anaphylactic reaction while eating in the cafeteria in his
dormitory. He had a past history of peanut allergy, as well
as moderate persistent asthma requiring combination
therapy with an inhaled corticosteroid and a long-acting
bronchodilator. He ingested chili which contained peanut
butter as a flavoring agent and developed immediate,
generalized urticaria, emesis, and an exacerbation of his
asthma with significant respiratory distress. He was
transported to a local emergency room for medical
management, including two doses of intramuscular
epinephrine, and was ultimately admitted for a 2-day
hospital stay.

This case example makes the point that although
the specific cause of anaphylaxis is frequently undetermined, food allergens can be responsible for
these severe reactions in a significant number of
cases.29,66 Until two decades ago, fatal food-induced
anaphylaxis had mainly consisted of anecdotal
reports of isolated cases. In 1988, Yuninger et al.27
reported a series of seven cases identified over a
16-month period. Five patients reacted to tree nuts
or peanuts. Four years later, Sampson et al.26
reported 13 fatal and near-fatal anaphylactic reactions in children and adolescents. Again, most
patients reacted to tree nuts or peanuts, and all
had a history of asthma. Moreover, respiratory
symptoms were prominent in all patients, and most
probably contributed to the outcome of the reaction. More recently, Bock et al.67 analyzed the
circumstances of 32 deaths after food-induced anaphylaxis reported to a national registry. Allergies
to peanuts and tree nuts were responsible for most.
In addition, all but one patient with adequate information were known to have asthma. These reports
highlight an increased risk for severe food-induced
anaphylaxis in patients with asthma, in particular
those requiring maintenance medications. Followup visits in these patients should emphasize the
importance of good asthma control, and should
assure the availability and proper instruction of the
use of self-injectable epinephrine.
To determine whether self-reported food allergy
is significantly associated with potentially fatal

8

childhood asthma, medical records from 72 patients
admitted to a pediatric intensive care unit (PICU)
for asthmatic exacerbation were reviewed and compared in a case–control study.68 Two control groups
included randomly selected groups of 108 patients
admitted to a regular nursing floor for asthma and
108 ambulatory patients with asthma. Factors evaluated included self-reported food allergy, gender,
age, residence in a poor area, race/ethnicity, inhaled
steroid exposure, tobacco exposure, length of hospital stay, psychological comorbidity and season of
admission. At least one food allergy was documented for 13% (38/288) of the patients. Egg,
peanut, fish/shellfish, milk and tree nut accounted
for 78.6% of all food allergies. Children admitted
to the PICU were significantly more likely to report
food allergy (p = 0.004) and 3.3 times more likely
to report at least one food allergy than children
admitted to a regular nursing floor. Furthermore,
the study subjects were significantly more likely to
report food allergy (p < 0.001) and 7.4 times more
likely to report at least one food allergy than children seen in the ambulatory setting. Self-reported
food allergy is an independent risk factor for potentially fatal childhood asthma. Asthmatic children or
adolescents with food allergy are a target population for more aggressive asthma management.
Finally, a 5-year retrospective review from Australia
summarized reports of children presenting with
anaphylaxis to a local emergency department.69
There were 123 cases of anaphylaxis in 117 patients;
one fatality was reported. Foods were by far the
most common trigger (86%), with peanuts and tree
nuts leading the list. Respiratory symptoms were
the principal presenting symptom (97%).

Patients with recurrent or chronic
asthma: routine testing for food allergy
Foods are often suspected in the quest for allergic
triggers of recurrent or chronic asthma. A clear link
between ingestion of a specific food and worsening
of asthma is only rarely reported. In one investigation,9 300 consecutive patients with asthma (age
range 7 months to 80 years) were evaluated in a
pulmonary clinic; 25 (12%) had a history of food
allergy suggested by clinical symptoms, and/or positive tests of food-specific IgE antibodies. Foodinduced wheezing was documented in six (2%) of
the cases; all were children aged 4–17 years. In
another investigation, 140 children, aged 2–9 years,
with asthma were screened by clinical history and
107

Food Allergy

testing for food-specific IgE antibodies.70 Of these
children, 32 were able to undergo blinded food challenges; 13 (9.2%) had food-induced respiratory
symptoms and eight (5.7%) had specific asthmatic
reactions documented during food challenges. Only
one patient had asthma as the sole symptom during
a positive food challenge. Interestingly, the patients
with food allergy and asthma were generally younger
and had a past medical history of atopic dermatitis.
In a similar investigation, Oehling and coworkers71 reported that food-induced bronchospasm was present in 8.5% of 284 asthmatic children
evaluated. The majority of the allergic sensitization
occurred in the first year of life and was caused by
a single food, especially egg. In addition, Businco
and colleagues72 evaluated 42 children (age range
10–76 months) with atopic dermatitis and milk
allergy. Eleven (27%) of these patients developed
asthmatic symptoms during a positive food challenge. Finally, an investigation from Turkey confirmed that food allergy can elicit asthma in children
less than 6 years of age; the incidence was 4%. The
most common food allergens implicated were egg
and cows’ milk.73
In order to evaluate food allergy as a risk factor
for severe asthma, Roberts and colleagues74 investigated 19 children with exacerbations of asthma
needing ICU ventilation. Compared to controls,
these patients had an increased risk of food allergy
(OR 8.58; 95% CI 1.85–39.71), multiple allergic
diagnoses (OR 4.42; CI 1.17–16.71) and frequent
asthma admissions (OR 14.2; CI 1.77–113.59). The
authors concluded that food allergy and frequent
asthma admissions appear to be significant independent risk factors for life-threatening asthmatic
events. As noted earlier, the association of increased
asthma morbidity with at least one food sensitization and the increasing morbidity with sensitization to increasing numbers of foods indicates that
food allergen sensitivity may be a marker for
increased asthma severity18 (Clinical Pearl 4).

Diagnosis/management
Medical history
The importance of a comprehensive medical history
in patients suspected of having food allergy or anaphylaxis will be reviewed in detail in Chapters 4 and
12. This history should include questions about the
timing of the reaction in relation to food ingestion,
108

CLINICAL PEARL #4

KEY POINTS RELATED TO FOOD ALLERGY
AND THE RESPIRATORY TRACT
• Food-induced respiratory tract symptoms are typically
accompanied by either cutaneous or gastrointestinal
symptoms; they rarely occur as isolated symptoms
• Allergic sensitization or clinical reactions to foods in
infancy predict the later development of respiratory
allergies and asthma
• Food-induced asthma is more common in young
pediatric patients than in older children and adults
• Children with atopic dermatitis, especially those with
food allergy confirmed during blinded food challenges,
are at increased risk for food-induced asthma
• Food-induced allergic reactions may increase airway
reactivity in some patients with moderate to severe
asthma and may do so without inducing acute asthma
symptoms
• Asthmatic reactions induced by food allergy are
considered risk factors for fatal and near-fatal
anaphylactic reactions

the minimum quantity of food required to cause
symptoms, specific upper and lower respiratory
signs and symptoms, the reproducibility of the
symptoms, and a current or past clinical history
of allergy to specific food allergens (e.g. egg).1,31,75
A family history of allergy and/or asthma can be a
useful historical point. When there is a history of an
unexplained sudden asthma exacerbation, details
about preceding food ingestion should be elicited. A
history of a severe or anaphylactic reaction following
the ingestion of a food may be sufficient to indicate
a causal relationship. Finally, the specific treatment
received and its response should be documented.

Physical examination
In evaluating patients with respiratory complaints
that may be induced by food allergy, the physical
examination can be useful. Findings here are
helpful in assessing overall nutritional status,
growth parameters and any signs of allergic disease,
especially atopic dermatitis. Moreover, this examination will help rule out other conditions that may
mimic food allergy.

Testing for food allergy
When used in conjunction with standard criterion
of interpretation, skin testing (e.g. percutaneous)
can give reliable clinical information in a short

The Respiratory Tract and Food Allergy

period of time (i.e. 15–20 minutes), and should
provide useful information in the overall evaluation of a patient with suspected food allergyinduced respiratory tract reactions. This specific
issue, as well as other diagnostic testing for food
allergy, is very thoroughly addressed in Chapter 13.
The routine use of skin testing to foods in patients
presenting with asthma is not appropriate. Of children evaluated in a tertiary care hospital emergency
room, 97 patients with asthma or bronchiolitis
were skin tested to common foods and aeroallergens. These results were compared to similar testing
in 60 control patients without any respiratory
disease.76 Most specific IgE antibody responses in
wheezing children were to aeroallergens and the
prevalence of specific IgE antibodies to food allergens was low. Laboratory assessment of food allergy
may include the measurement of food-specific IgE
in the serum. When highly sensitive assays are used,
the sensitivity and specificity are similar to those
of skin tests.77–79 In contrast, basophil histamine
release assays, which are mainly limited to research
settings, have not been shown conclusively to be a
reproducible, diagnostic test for food allergy.80

Food challenges
When there is clinical suspicion of a food-induced
respiratory tract reaction and the test for specific IgE
antibody to the food is positive, an elimination diet
may be implemented to see if there is a resolution
of clinical symptoms. Confirming this association,
however, can be very difficult. Food challenges can
be very useful and reliable in the diagnostic evaluation of a patient with food-induced respiratory
symptoms. Chapter 14 provides an excellent overview of oral food challenge procedures (Clinical
Pearl 5).

Treatment
Once a food allergy has been confirmed as a cause
for respiratory tract symptoms, strict avoidance of
the offending food is necessary.1,23,80 A properly
managed elimination diet can lead to resolution of
clinical symptoms such as chronic asthma. Appropriate nutritional counseling is important to ensure
that an elimination diet is well balanced, to provide
appropriate substitutes for foods that are eliminated
from the diet, and to avoid any anticipated nutritional deficiencies, such as calcium deficiency.36

8

CLINICAL PEARL #5

KEY POINTS RELATED TO THE EVALUATION
OF FOOD ALLERGY AND RESPIRATORY
SYMPTOMS
• The medical history supplemented with appropriate
laboratory testing and well-designed food challenges
can provide useful information in the workup of patients
with respiratory symptoms that may be induced by food
allergy; a diagnosis based solely on history or skin
testing/allergen-specific IgE levels is not acceptable.
• If no specific foods are implicated in the history and if
skin tests to foods are negative, further workup for
IgE-mediated allergy is not generally indicated.
• With positive skin tests and/or respiratory symptoms
associated with specific foods, an elimination diet may
be instituted for 7–14 days; if symptoms persist, food is
not likely to be the problem, except in some cases of
atopic dermatitis or chronic asthma.
• Symptoms recurring after a regular diet is resumed
should be evaluated with a properly designed food
challenge.

Growth parameters should be closely monitored,
especially in infants and children on elimination
diets. An overview of the management of food
allergy and the development of an appropriate anaphylaxis treatment plan, including the use of injectable epinephrine for anaphylactic symptoms, is
addressed in Chapter 15.

Summary and conclusions
Previous investigations have clearly established the
pathogenic role of food allergy in respiratory tract
symptoms. These symptoms are typically accompanied by skin and gastrointestinal manifestations
and rarely occur in isolation. Specific foods have
been implicated in these reactions, and a small
well-identified subset of foods has been associated
with anaphylactic reactions. Allergic sensitization
to foods in infancy may predict the later development of respiratory allergies and asthma. Asthmatic
reactions to food additives can occur but are uncommon. Food-induced asthma is more common in
younger, pediatric patients, especially those with
atopic dermatitis, than in older children and adults.
Asthma may be triggered by the inhalation of relevant food allergens at all ages. Asthma, induced by
food allergens, is considered a significant risk factor
for fatal and near-fatal anaphylactic reactions.
109

Food Allergy

Studies have demonstrated that foods can elicit
airway hyperreactivity and asthmatic responses;
therefore, evaluation for food allergy should be
considered in patients with difficult to control
asthma or otherwise unexplained acute severe
asthma exacerbations; asthma triggered following
ingestion or inhalation of particular foods; and in
asthmatic patients with other manifestations of
food allergy (e.g. anaphylaxis, moderate to severe
atopic dermatitis). Practice parameters for the diagnosis and treatment of asthma have highlighted the
potential role of food allergy in asthma in some
patients.81,82

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and scallops. Ann Allergy Asthma Immunol
2000;85:461–6.
41. Crespo JF, Pascual C, Dominguez C, et al. Allergic
reactions associated with airborne fish particles in
IgE-mediated fish hypersensitive patients. Allergy
1995;50:257–61.
42. Pascual CY, Reche M, Flandor A, et al. Fish allergy in
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43. Taylor AV, Swanson MC, Jones RT, et al. Detection and
quantification of raw fish aeroallergens from an
open-air fish market. J Allergy Clin Immunol
2000;105:166–9.
44. Eigenmann PA, Zamora SA. An internet-based survey
on the circumstances of food-induced reactions
following the diagnosis of IgE-mediated food allergy.
Allergy 2002;57:449–53.
45. Roberts G, Golder N, Lack G. Bronchial challenges
with aerosolized food in asthmatic food-allergic
children. Allergy 2002;57:713–7.
46. Sicherer SH, Furlong TJ, DeSimone J, et al. Selfreported allergic reactions to peanut on commercial
airliners. J Allergy Clin Immunol 1999;104:186–9.
47. James JM, Bernhisel-Broadbent J, Sampson HA.
Respiratory reactions provoked by double-blind food
challenges in children. Am J Respir Crit Care Med
1994;149:59–64.
48. Bernstein JM. The role of IgE-mediated hypersensitivity
in the development of otitis media with effusion: A
review. Otolaryngol Head Neck Surg 1993;109:611–20.
49. Nsouli TM, Nsouli SM, Linde RE, et al. Role of food
allergy in serous otitis media. Ann Allergy
1994;73:215–9.
50. Heiner DC, Sears JW. Chronic respiratory disease
associated with multiple circulation precipitins to cow’s
milk. Am J Dis Child 1960;100:500–2.
51. Heiner DC, Sears JW, Kniker WT. Multiple precipitins
to cow’s milk in chronic respiratory disease: A
syndrome including poor growth, gastrointestinal
symptoms, evidence of allergy, iron deficiency anemia
and pulmonary hemosiderosis. Am J Dis Child
1962;103:634–54.
52. Lowe AJ, Hosking CS, Bennett CM, et al. Skin prick test
can identify eczematous infants at risk of asthma and
allergic rhinitis. Clin Exp Allergy 2007;37:1624–31.
53. Tepper RS, Llapur CJ, Jones MH, et al. Expired nitric
oxide and airway reactivity in infants at risk for
asthma. J Allergy Clin Immunol 2008;122:760–5.

8

54. Priftis KN, Mermiri D, Papadopoulou A, et al. Asthma
symptoms and bronchial reactivity in school children
sensitized to food allergens in infancy. J Asthma
2008;45:590–5.
55. Hill DJ, Firer MA, Shelton MJ, et al. Manifestations of
milk allergy in infancy: clinical and immunological
findings. J Pediatr 1986;109:270–6.
56. Bock SA. Respiratory reactions induced by food
challenges in children with pulmonary disease. Pediatr
Allergy Immunol 1992;3:188–94.
57. Rance F, Dutau G. Asthma and food allergy: report of
163 cases. Arch Pediatr 2002;9:402–7.
58. Fiocchi A, Terracciano L, Bouygue GR, et al.
Incremental prognostic factors associated with cow’s
milk allergy outcomes in infant and child referrals: the
Milan Cow’s Milk Allergy Cohort study. Ann Allergy
Asthma Immunol 2008;101:166–73.
59. James JM, Eigenmann PA, Eggleston PA, et al. Airway
reactivity changes in asthmatic patients undergoing
blinded food challenges, Am J Respir Crit Care Med
1996;153:597–603.
60. Prifits KN, Mermiri D, Papadopoulou A, et al.
Asthma symptoms and reactivity in school children
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2008;45:590–5.
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examination of food hypersensitivity as a cause of
increased bronchial responsiveness to inhaled
methacholine. J Allergy Clin Immunol 1991;88:360–4.
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Increased frequency of asymptomatic bronchial
hyperresponsiveness in nonasthmatic patients with
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sputum analysis and skin prick test to inhalant
allergens in patients with symptomatic food
hypersensitivity. Isr Med Assoc J 2005;7:781–4.
64. Wallaert B, Gosset P, Lamblin C, et al. Airway
neutrophil inflammation in nonasthmatic patients
with food allergy. Allergy 2002;57:405–10.
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anaphylaxis: a 5 year retrospective review. Allergy
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72. Businco L, Falconieri P, Giampietro P, et al. Food
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(IgE antibody) to food allergens in wheezing infants
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266–70.

112

77. Sampson HA, Ho DG. Relationship between foodspecific IgE concentrations and the risk of positive food
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Immunol 1997;100:444–51.
78. Sampson HA. Utility of food specific IgE
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food-allergic patients and their allergens by the RAST
technique and clinical investigation, Clin Allergy
1979;9:25–36.
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Immunol (supplement) 1996;96:707–869.

CHAPTER

9 

Food-induced Anaphylaxis and Food
Associated Exercise-induced
Anaphylaxis
Motohiro Ebisawa

KEY CONCEPTS
The most common food triggers for anaphylaxis are
peanut, tree nuts, cows’ milk, hens’ egg, fish and
shellfish. However, in some regions wheat, buckwheat,
lipid transfer protein-related fruits and bird’s nest can
also provoke food-induced anaphylaxis.
 The incidence of food-dependent exercise-induced
anaphylaxis has increasingly been reported during the
past three decades. Wheat, crustaceans and vegetables
are the most common food triggers for the disease in
recent reports.
 Comorbidities (e.g. asthma) and risk factors (NSAIDs,
exercise etc.) may affect symptom severity and


Introduction
Historical background
Fatal allergic reactions were reported more than
1000 years ago, but it was only 100 years ago that
the term of ‘anaphylaxis’ was fully established. In
1902, Portier and Richet1 first described the sudden
death of several dogs involved in immunization
trials against the venom of the sea anemone.
As this phenomenon represented the opposite of
the intended ‘prophylaxis’ of immunization, they
created the term ‘anaphylaxis’, meaning a phenomenon without or against the protection. In 1969,
10 cases of anaphylaxis following the ingestion of
various foods, including different legumes, fish and
milk, were reported. Furthermore, the natural course
© 2012, Elsevier Inc

treatment response in patients with food-induced
anaphylaxis or food-dependent exercise-induced
anaphylaxis.
 Adrenaline is the first line of therapy and its
administration is strongly recommended in all cases
as soon as the first symptoms of anaphylaxis are
recognized.
 Long-term management, including avoidance of
causative foods and an emergency management
prescription including self-injectable adrenaline, is
essential in patients with food-induced anaphylaxis.

of near-fatal and fatal food-induced anaphylactic
reactions has been further reported by US researchers in the last 30 years.1
The first case of food-dependent exercise-induced
anaphylaxis (FEIAn or FDEIA) was reported by
Mauliz et al. in 1979.2 This patient was a runner
who often developed anaphylactic reactions after
having meals with shellfish prior to his routine
running activity. Since this initial case report, the
incidence of FDEIA appears to be increasing over
the past few decades.

Definition of anaphylaxis
Based on the World Health Organization (WHO)
definition, anaphylaxis is ‘a severe, life-threatening
generalized or systemic hypersensitivity reaction’.

Food Allergy

However, this definition can be problematic, given
that the term ‘life-threatening’ may be interpreted
differently by different healthcare providers. A
recent meeting in the US sponsored by the National
Institute of Allergy and Infectious Disease (NIAID)
and the Food Allergy and Anaphylaxis Network
(FAAN) has established a consensus definition to
satisfy epidemiological, research and clinical needs.3
According to this definition, anaphylaxis is considered likely if any one of the following three criteria

is present within minutes to hours after the onset
of the reaction (Table 9.1).
Symptoms of anaphylaxis can include cutaneous,
respiratory, cardiovascular and gastrointestinal (GI)
signs and symptoms either isolated or in combination. A grading system evaluating the severity of
food-induced anaphylaxis might be helpful and is
shown in Table 9.2.4
The clinical syndrome of FDEIA is characterized
by the rapid onset of anaphylaxis during (or soon

Table 9.1  Definition of anaphylaxis (Sampson HA, Muñoz-Furlong A, Campbell RL, et al. Second symposium on the definition
and management of anaphylaxis: summary report. J Allergy Clin Immunol 2006; 117: 391–7.)

1.  Acute onset of illness with cutaneous and/or mucosal involvement AND at least one of the following:
a.  Respiratory compromise (e.g. dyspnea, bronchospasm, stridor, hypoxia)
b.  Cardiovascular compromise (e.g. hypotension, collapse)
2.  Two or more of the following occur rapidly after exposure to a likely allergen (minutes to several hours):
a.  Involvement of skin or mucosa (e.g. generalized hives, itch, flushing, swelling)
b.  Respiratory compromise
c.  Cardiovascular compromise
d.  Or persistent gastrointestinal symptoms (e.g. crampy abdominal pain, vomiting)
3.  Hypotension after exposure to known allergen for that patient (minutes to several hours): age-specific low blood pressure* or
> 30% decline from baseline (or less than 90 mmHg for adults).
*Hypotension for children is defined as systolic blood pressure <70 mmHg from 1 month to 1 year, <(70 mmHg+[2×age]) from 1 to 10 years, and
<90 mmHg from 11 to 17 years.

Table 9.2  Grading of food-induced anaphylaxis according to severity of clinical symptoms (Sampson HA. Anaphylaxis
and emergency treatment. Pediatrics. 2003; 111: 1601–8.)

Grade

Skin

GI Tract

Respiratory tract

Cardiovascular

Neurological

1

Localized pruritus,
flushing, urticaria,
angioedema

Oral pruritus, oral
‘tingling’, mild lip
swelling







2

Generalized pruritus,
flushing, urticaria,
angioedema

Any of the above,
nausea and/or
emesis × 1

Nasal congestion,
and/or sneezing



Change in
activity level

3

Any of the above

Any of the above
plus repetitive
vomiting

Rhinorrhea, marked
congestion,
sensation of throat
pruritus or tightness

Tachycardia
(increase
>15 bpm)

Change in
activity level
plus anxiety

4

Any of the above

Any of the above
plus diarrhea

Any of the above,
hoarseness, ‘barky’
cough, difficulty
swallowing, dyspnea,
wheezing, cyanosis

Any of the above,
dysrhythmia and/
or mild
hypotension

‘Light
headedness’,
feeling of
‘pending doom’

5

Any of the above

Any of the above,
loss of bowel
control

Any of the above,
respiratory arrest

Severe
bradycardia, and/
or hypotension or
cardiac arrest

Loss of
consciousness

114

Food-induced Anaphylaxis and Food Associated Exercise-induced Anaphylaxis

after) exercise which was preceded by the ingestion
of the causal food(s). Both the food allergen and
exercise are independently tolerated.5

9

Epidemiology

anaphylaxis, and data will be summarized in four
categories described below. Most data on foodinduced anaphylaxis were obtained from hospital
ED (emergency department) based-studies or
questionnaires in selected populations.

Food-induced anaphylaxis

Reports on children

The true prevalence of food-induced anaphylaxis is
not well established, since it was only recently that
International Classification of Diseases Code (ICD)
for food-induced anaphylaxis was defined. Therefore, it is still difficult to obtain reliable information
regarding its prevalence, incidence or mortality
rates. Furthermore, it is suspected that adults with
less severe cases of food-induced anaphylaxis, tend
to avoid causative foods without consulting
physicians.
Accordingly, limited information on foodinduced anaphylaxis is currently available. This
chapter will review recent reports on food-induced

Reports from various areas of the world on foods
involved in anaphylaxis in children are summarized
in Table 9.3. In reports from the USA, the most
frequent food to cause anaphylaxis are peanuts, followed by tree nuts, cows’ milk and cows’ milk
protein-based products, as well as shellfish. Data
from the USA were mostly collected in hospital
emergency departments (ED) or referral outpatient
clinics. Two reports from Australia, with ED-based
analysis, were using the corresponding ICD codes
for anaphylaxis. Similarly to the USA, the most
common causative foods were peanuts, cows’ milk,
cashew nuts and eggs. More reports were from Asia,

Table 9.3  Causes of food-induced anaphylaxis in children

Study

Country

Publication
year

Most frequent causative foods
1st

2nd

3rd

Cases (n)

Ref.

Järvinen
KM et al.

USA

2008

Peanuts

Cows’ milk

Nuts

95

J Allergy Clin
Immunol
122: 133–138

Rudders
SA et al.

USA

2010

Peanuts

Cows’ milk

Nuts

846

J Allergy Clin
Immunol
126: 385–388

Russell S
et al.

USA

2010

Peanuts

Shellfish

Cows’ milk

124

Pediatr
Emerg Care
26: 71–76

Braganza
SC et al.

Australia

2006

Dairy

Egg

Peanuts

de Silva
IL et al.

Australia

2008

Peanuts

Cashew nut

Cows’ milk

104

Allergy 63:
1071–1076

Goh DL
et al.

Singapore

1999

Bird’s nest

Crustacean
seafood

Egg and
milk

124

Allergy 54:
84–86

Piromrat
K et al.

Thailand

2008

Prawn

Imai T

Japan*

2004

Hen’s egg

57

Arch Dis
Child 91:
159–163

Asian Pac J
Allergy
Immunol 26:
121–128
Cows’ milk

Wheat

408

Arerugi 52:
1006–1013

*Infant only.

115

Food Allergy
Table 9.4  Causes of food-induced anaphylaxis in adults

Study

Country

Publication
year

Most frequent causative foods
1st

2nd

3rd

Greenhawt
MJ et al.

USA

2009

Cows’ milk

Nuts

Shellfish

Asero R
et al.

Italy

2009

Peach

Shrimp

Nuts

MoneretVautrin DA
et al.

France

1995

Hen’s egg

Fish or
crustaceans

milk or
fruit-latex
group

Brown AF
et al.

Australia

2001

Fish and
Seafood

Nuts

Mango or
Lemon drink

Imai T

Japan

2004

Fish

Buckwheat

Meat

including Singapore and Japan (the latter one
with hospital ED-based data). Unlike the USA and
Australia, the common causative foods in children
were hens’ eggs, cows’ milk and wheat products.
Interestingly, bird’s nest and crustaceans were
reported as the top two foods responsible for foodinduced anaphylaxis in Singapore. These data clearly
show geographically and environmentally related
causes for food-induced anaphylaxis in children.

Reports in adults
Reports on food-induced anaphylaxis in adulthood
are less frequent than those for children. As shown
in Table 9.4, reports from the USA involved college
students, with common food triggers being cows’
milk, tree nuts, shellfish and peanuts. In Italy, hospital ED-based reports revealed that peach was the
most common food to induce anaphylaxis, followed
by shrimp, tree nuts and legumes other than peanut.
In France, hen’s egg, fish, crustaceans and cows’ milk
were reported to be common foods to induce anaphylaxis. In Australia, fish and seafood were reported
to be the most common causative foods, followed
by tree nuts and mango- or lemon-containing
drinks. In Japan, fish and buckwheat were reported
to be the top two causative foods in hospital
ED-based surveys. These data were mostly obtained
from multicenter or single-hospital ED-based
studies, suggesting a potential population bias.
116

Cases (n)

Ref.

104

J Allergy Clin
Immunol 124:
323–327

58

Int Arch Allergy
Immunol 150:
271–277

794

Ann
Gastroenterol
Hepatol 31:
256–263

22

J Allergy Clin
Immunol 108:
861–866

130

Arerugi 52:
1006–1013

Reports including all age groups
Table 9.5 summarizes four reports on the incidence
of food-induced anaphylaxis including both children and adults from various different regions of
the world. In the USA, similarly to the previously
cited reports, tree nuts, crustaceans and peanut were
the top three causative foods. In Korea, wheat,
buckwheat and seafood are top of the list. Buckwheat seems to be a common food trigger to
induce anaphylaxis in both Korea and Japan, where
noodles made of buckwheat are commonly eaten.
Buckwheat-like wheat can be not only a food allergen but also an aeroallergen, especially for workers
in buckwheat noodle factories. As buckwheat is
now becoming a common food in countries such
as the USA and France, one might suspect a progression of buckwheat allergy throughout the world. In
Japan, cows’ milk, hen’s egg, and wheat products
were reported to be the three major food suspects;
the study included more children than adults

Reports on fatal cases of anaphylaxis
Although detailed data on fatal anaphylaxis are
limited, several recent publications from the USA,
UK, Australia and Japan report on fatal foodinduced anaphylaxis (Fig. 9.1). A careful search for
fatal cases of food-induced anaphylaxis in the UK
revealed 48 deaths between 1999 and 2006. A

Food-induced Anaphylaxis and Food Associated Exercise-induced Anaphylaxis

9

Table 9.5  Causes of food-induced anaphylaxis from childhood to adulthood

Study

Country

Publication
year

Age

Most frequent causative foods
1st

2nd

USA

2008

2–66 y

Seafood

nuts

Yang MS
et al.

Korea

2008

5–76 y

Wheat flour

Buckwheat

Seafood

Imamura
T et al.

Japan

2008

0–93 y

Milk

Eggs

Wheat

Cianferoni
A et al.

Italy

2001

?

Seafood

Peanut
20
Tree nuts 10
Milk
1
Fish
1
*Including a case
with an uncertain
trigger food
JACI 2001,
107:191-3

USA
2001–2006
31 cases
Peanut
17
Tree nuts 8
Milk
4
Fish
1

UK
1999–2006
48 cases
Peanut
Nuts
Milk
Fish
Shellfish
Snail
Sesame
Egg
Tomato
(uncertain

18)

JACI 2007,
119:1016-8

23

J Allergy
Clin
Immunol
121:
166–171

29

Ann
Allergy
Asthma
Immunol
100:
31–36

319

Pediatr
Allergy
Immunol
19:
270–274

113

Ann
Allergy
Asthma
Immunol
87: 27–32

Japan
1999–2004
4 cases

9
9
6
1
1
1
1
1
1

JACI 2007,
119:1018-9

Ref.

3rd

Ross MP
et al.

USA
1994–1999
32 cases*

Cases (n)

Shrimp
Buckwheat
Fish
Chocolate

1
1
1
1

Nihon Kyukyu
Igakukai Zasshi
2005, 16:564-6

Australia
1997–2005
7 cases
Peanut
Fish

3
1

(no information 1)
(undetermined 2)
JACI 2009,
123:434-42

Figure 9.1  Worldwide cases of fatal food-induced anaphylaxis.

117

Food Allergy

voluntary registry initiated by the American
Academy of Allergy, Asthma and Immunology
(AAAAI) and the Food Allergy and Anaphylaxis
Network (FAAN) collected 32 cases of fatal foodinduced anaphylaxis between 1994 and 1999 and
a further 31 cases between 2001 and 2006. There
were 112 anaphylaxis fatalities in Australia between
1997 and 2005, of which seven (6.3%) were attributed to food. Through the national mortality
reporting system in Japan, each year several cases
of food-induced anaphylaxis fatalities have been
reported in the last 15 years. Compared to the
number of anaphylaxis deaths in the UK or the
USA, food-induced anaphylaxis reports are relatively less frequent in Australia and Japan. In the
USA, the UK and Australia, peanut was reported to
be the most frequent food to cause fatal anaphylaxis. Other than peanut or tree nuts, any kind of
food, such as shellfish, fish and cows’ milk, can be
a potential trigger for fatal food-induced anaphylaxis. It needs to be pointed out that in the reports
cited above, most of the individuals did not have
epinephrine available at the time of their fatal reaction. With regard to comorbid conditions, asthma
was reported to be the most important risk factor
for death.
Summarized from these data on food-induced
anaphylaxis from childhood to adulthood, the
most common foods involved are peanut, tree nuts,
cows’ milk, hen’s egg, fish, and crustacean shellfish.
However, in some regions, wheat, buckwheat, lipid
transfer protein (LTP)-related fruits such as peach
or Kiwi fruit, and bird’s nest were commonly identified triggers. Also, the incidence may vary according
to age, regional diet, food preparation, amount of
exposure, and timing of first exposure.

Reports on food-dependent
exercise-induced anaphylaxis
The incidence of FDEIA seems to be increasing
since the first report by Mauliz et al. in 1979.2
Reports from all over the world are summarized in
Table 9.6. Wheat, crustaceans and vegetables are
reported as the most common triggers. Aihara6
reported the prevalence of (FEIAn or FDEIA) in
junior high-school students in Japan to be 0.017%
(13/76229). He also reported on 84 cases from
various countries which occurred between 1979
and 2004.7 As shown in Figure 9.2, FDEIA was most
frequently seen in teenagers and young adults, and

118

the most common causative foods were wheat, vegetables and tree nuts (Table 9.7).

Pathogenesis
Causative food allergens absorbed in the gut may
lead to anaphylaxis through a mechanism that
involves cross-linking of IgE and aggregation of
FcεRI on mast cells and basophils (described
in more detail in Chapter 1). In humans, foodinduced anaphylaxis is mostly IgE driven. Intracellular events, including activation of tyrosine kinases
and calcium influx in mastocytes and basophils,
result in the rapid release of preformed mediators
such as histamine, tryptase and chymase. Activation
of phospholipase A2, COXs, and lipooxygenases
leads to the production of arachidonic acid metabolites, including prostaglandins and leukotrienes,
and synthesis of platelet-activating factor. Various
cytokines and chemokines are further synthesized
and released, which may play a role in the latephase reaction. Increased permeability of the
endothelial barrier through endothelial Gq/G11mediated signaling has been identified as a critically important process leading to symptoms of
anaphylaxis in several organs.8
Relatively few protein families account for the
vast majority of allergic reactions. A study by Jenkins
et al.9 comparing food allergens of animal origin
and their human homologs (by analyzing protein
families, sequence analysis and evolutionary features) disclosed that sequence identities to human
homologs > 62% typically excluded the protein
from being allergenic in humans. It has been shown
that major food allergens share a number of
common features: they are water-soluble glycoproteins, 10–70 kDa in size, and relatively stable to
heat, acid and proteases.
Host conditions, including diseases, medications,
infections and exercise, have also been associated
with the pathogenesis of food-induced anaphylaxis,
as discussed later in this chapter.
Overall, the pathogenesis of FDEIA is not well
understood. One possible explanation for FDEIA
would be increased gut permeability during exercise, resulting in larger amounts of potentially allergenic proteins reaching the host’s gut-associated
immune system. Gut permeability has been shown
to be increased in food-allergic and food-intolerant
children.5

2009
2002

2001
1999

Japan

Japan

Japan

Korea

Singapore

France

Italy

USA

Harada S et al.

Harada S et al.

Aihara Y et al.

Yang MS et al.

Teo SL et al.

MathelierFusade P et al.

Romano A
et al.

Shadick NA
et al.

2008

2001

2000

2000

2000

Japan

Kano H et al.

Publication year

Country

Study

13–77 y

?

?

9–20 y

5–76 y

12–15 y

<20 y

>20 y

9–43 y

Age

Shellfish

Tomatoes

Wheat

Shellfish

Wheat

Shrimps
and crab

Shrimp

Wheat

Wheat

1st

Alcohol

Wheat

Corn,
barley,
shrimp,
apple,
paprika,
mustard

Apple
or
shrimp

Wheat

Wheat

Shrimp

Shrimp

2nd

Foods triggering FEIAn

Tomatoes

Peanuts

Grapes,
vegetables,
buckwheat

Shellfish or
fish

3rd

Table 9.6  Summary of worldwide multiple food-dependent exercise-induced anaphylaxis case reports

279 (EIA
patients)

54

7

5

18

13

167

167

18

Cases (n)

J Allergy Clin Immunol 104: 123–127

Int Arch Allergy Immunol 125:
264–272

Ann Dermatol Venereol 129: 694–697

Ann Acad Med Singapore 209:
905–909

Ann Allergy Asthma Immunol 100:
31–36

J Allergy Clin Immunol 108:
1035–1039

Arerugi 49: 1066–1073

Arerugi 49: 1066–1073

Arerugi 49: 472–478

Ref.

Food-induced Anaphylaxis and Food Associated Exercise-induced Anaphylaxis

9

119

Food Allergy

(n)
40
30
20
10
0

0–

10–

20–

30–
40–
Age

50–

60–

70–
n = 84

Figure 9.2  Age distribution of food-dependent exercise-

Figure 9.3  Food-induced anaphylaxis (after wheat challenge).

induced anaphylaxis reported from 1979 to 2004. Aihara Y.
[Food-dependent exercise-induced anaphylaxis]. Arerugi. 2007
May; 56(5): 451–6.

4-year-old boy with a skin rash, wheezing and dyspnea.

Table 9.7  Causative foods of FEIAn reported from 1979 to
2004. Aihara Y. [Food-dependent exercise-induced
anaphylaxis]. Arerugi. 2007 May; 56(5): 451–6.

Food

Case (n)

(%)

Wheat

29

(38.2)

Vegetable

24

(31.6)

Nut

16

(21.1)

Fruit

7

(9.2)

Plant oil

4

(5.3)

Shellfish

3

(3.9)

6

(7.9)

Others
Total

76

Clinical features
Food-induced anaphylaxis
The symptoms of anaphylaxis are generally related
to the skin, the respiratory or GI tracts and the cardiovascular system.10 Figure 9.3 shows a patient
with typical skin symptoms. The patient is a 4-yearold boy who experienced anaphylaxis after receiving the initial dose of wheat challenge during an
in-hospital test. In addition to skin symptoms, he
developed wheezing and oxygen saturation <90%.
He received intramuscular epinephrine twice, and
120

recovered from his anaphylactic reaction. Skin
symptoms, which occur in most patients, may
include itching, flushing, urticaria and angioedema.
However, it is important to realize that anaphylaxis
can occur without skin manifestations. Respiratory
symptoms, which frequently occur in anaphylaxis,
include nasal symptoms, laryngeal edema, choking,
wheezing, coughing and dyspnea. Gastrointestinal
symptoms include abdominal pain and cramping,
nausea, vomiting and diarrhea. Cardiovascular
symptoms, such as hypotension and shock, are less
common as early manifestations of food-induced
anaphylaxis. The time course of the reaction and
the perception of symptoms and signs differ among
individuals.1
Biphasic allergic reactions, defined as a second
reaction occurring 1–72 hours after recovery from
the initial reactions, were reported in 11% of children treated for anaphylaxis in a pediatric ED.
Biphasic reactions were reported in 25% of cases of
fatal and near-fatal food-induced reactions and
23% of drug/biological-induced reactions, but in
only 6% of anaphylaxis due to other causes. They
are uncommon after insect stings. It is important to
note that biphasic reactions rarely occur without
initial hypotension or airway obstruction.11

Food-dependent exercise-induced
anaphylaxis
CLINICAL CASE
Figure 9.4 illustrates a case of FDEIA . The patient is a
14-year-old student in junior high school who ate seafood

Food-induced Anaphylaxis and Food Associated Exercise-induced Anaphylaxis

9

patients with food-induced anaphylaxis. Two specific conditions might be highlighted.



Figure 9.4  A case of food-dependent, exercise-induced
anaphylaxis. A 14-year-old junior high-school student developed
anaphylaxis after eating seafood for lunch, followed by playing
football with his friends.

for lunch and played football with his friends immediately
afterwards. During the game his skin began to itch he
developed a strange feeling in his mouth. He also
developed severe eyelid edema, laryngeal edema and a
blister on the uvula. He had difficulty in breathing and lost
consciousness during transfer to the ED owing to a drop in
his blood pressure to 80 mmHg systolic. He received
appropriate treatment in the ED, including several
injections of intramuscular epinephrine, and was carefully
monitored, including an overnight stay for further careful
observation. A case series of Japanese schoolchildren
reported the following symptoms among those with
food-dependent exercise-induced anaphylaxis: pruritus
(92%), urticaria (86%), angioedema (72%), flushing (70%),
shortness of breath (51%), dysphagia (34%), chest
tightness (33%), fainting (32%), profuse sweating (32%),
headache (28%), gastrointestinal symptoms (colic, nausea
and diarrhea) (28%), and upper airway symptoms (choking,
hoarse, throat constriction)(25%).11 Although FDEIA may
lead to life-threatening anaphylaxis with airway
obstruction and/or hypotensive shock, reports of fatalities
are rare and restricted to adults. However, fatalities may be
underestimated due to the rarity of the disease and the
difficulty of making a diagnosis.

Unusual variants
Late-onset food-induced anaphylaxis
Onset of an anaphylactic reaction usually occurs
within 30 minutes after exposure to the relevant
allergen. Isolated late anaphylactic reactions
without early-phase reactions are rarely reported in

Natto (soybeans fermented by the bacteria
Bacillus natto) anaphylaxis. Inomata et al.12
reported the first case of IgE-mediated skin,
respiratory and abdominal symptoms
occurring 10–12 hours after consuming
natto.
• Meat anaphylaxis. Commins et al.13 described
a cohort of 24 patients with IgE antibodies to
α-gal who experienced delayed symptoms of
anaphylaxis, angioedema or urticaria after
eating mammalian meat. The patients
described a similar history of anaphylaxis or
urticaria 3–6 hours after the ingestion of meat
and reported fewer episodes or complete
recovery when following an avoidance diet.
Skin prick tests to mammalian meat produced
wheals of usually <4 mm, whereas intradermal
or fresh-food skin prick tests elicited larger and
more consistent wheal responses. In vitro
testing revealed positive specific IgE antibodies
to beef, pork, lamb, cows’ milk, cat and dog,
but not to turkey, chicken or fish.

Associated condition worsening foodinduced anaphylaxis or food-dependent
exercise-induced anaphylaxis
Associated conditions and risk factors may affect
symptom severity and treatment response in
patients with food-induced anaphylaxis or FDEIA8
(Table 9.8). Bronchial asthma is the most important risk factor for a more severe outcome. Persistent asthma, especially if not well controlled, is an
impo­rtant risk factor for fatal anaphylaxis, in particular in adolescents and young adults. Cardio­
vascular disease is also an important risk factor,
especially in elderly patients. Common viral or
bacterial infections are also known to affect
symptom severity, especially in cases of gastro­
intestinal infections. Various medications, such as
β-blockers, angiotensin-converting enzyme inhibitors, α-adrenergic blockers, and non-steroidal antiinflammatory drugs (NSAIDs), may also affect
symptom severity and treatment response in
patients with food-induced anaphylaxis. Nonsteroidal anti-inflammatory drugs have also been
shown to enhance the symptoms of FDEIA. Alcohol
intake, fatigue, stress and exercise are known to
worsen symptoms and the severity of food-induced
anaphylaxis or FDEIA.8
121

Food Allergy
Table 9.8  Comorbid conditions and risk factors for food-induced anaphylaxis and food-dependent
exercise-induced anaphylaxis

Factors
Disease

FIA
Asthma*

DEIA

Ref.
J Allergy Clin Immunol. 2009; 124: 625



Clin Exp Immunol. 2008; 153: 7

Cardiovascular disease


Curr Opin Allergy Clin Immunol. 2007; 7: 337

Medication

J Allergy Clin Immunol. 2010; 125: S161

Infection



Other disorder**



J Allergy Clin Immunol. 2010; 125: S161



β-Adrenergic antagonists



Curr Allergy Asthma Rep. 2008; 8: 37

Angiotensin-converting enzyme (ACE) inhibitors



Curr Allergy Asthma Rep. 2008; 8: 37

α-Adrenergic blockers



Curr Allergy Asthma Rep. 2008; 8: 37

Antidepressants



Curr Allergy Asthma Rep. 2008; 8: 37
J Dermatol Sci. 2007; 47: 109

NSAIDs, aspirin




Br J Dermatol. 2001; 145: 336
Other

Alcohol intake





Addict Biol. 2004; 9: 195

Fatigue





J Allergy Clin Immunol. 2010; 125: S161

Stress





J Allergy Clin Immunol. 2010; 125: S161

Type of exercise





J Allergy Clin Immunol. 2010; 125: S161



J Allergy Clin Immunol. 2010; 125: S161

Atmospheric and seasonal conditions
* In particular if poorly controlled.

** 1) Mastocytosis and clonal mast cell disorder, 2) chronic lung disease, 3) anatomical airway obstruction , 4) depression and other psychiatric
disease.

Diagnosis
Food-induced anaphylaxis
The diagnosis of food-induced anaphylaxis is based
on clinical findings and a detailed description of the
acute episode, in association with known or suspected food exposure.1 As mentioned in the Introduction, new diagnostic criteria for anaphylaxis
were published recently with the intention to help
clinicians both to recognize the spectrum of signs
and symptoms that comprise anaphylaxis and to
establish a more systematic diagnostic and management approach.3 As shown in Table 9.1, the presence
of any one of three clinical criteria indicates that
anaphylaxis is highly likely. As already mentioned
(Table 9.2), a grading system evaluating the severity
of food-induced anaphylaxis might be useful.4
Laboratory tests are of limited value in the acute
phase of anaphylaxis. The clinical diagnosis may be
supported by the measure of serum tryptase within
6–8 hours after the beginning of the reaction.

122

Further tests at a follow-up visit will help to identify
the culprit food allergen. Skin prick and serum
allergen-specific IgE testing (e.g. ImmunoCAP) may
provide information about a specific food allergy
sensitization, but do not provide definite information regarding the cause of or risk for anaphylaxis.
Oral food challenge tests (ideally a double-blind
placebo-controlled food challenge) are useful for a
definite diagnosis in selected cases.

Food-dependent exercise-induced
anaphylaxis
A detailed clinical history is essential, and skin prick
and serum allergen-specific IgE testing may also
provide information regarding sensitization to a
specific food. The combination of the clinical history
and the support of allergy testing may provide
enough information to make an accurate diagnosis.
However, some patients with FDEIA may have negative results on allergy testing. In the case of wheatdependent exercise-induced anaphylaxis, it has been

Food-induced Anaphylaxis and Food Associated Exercise-induced Anaphylaxis

Medical history

spIgE, SPT (prick to prick)

Exercise challenge
If negative

If positive

Food + exercise
provocation

Exercise-induced
anaphylaxis

If negative

If positive

Aspirin + food + exercise provocation

If negative

If positive

Food-dependent
exercise-induced
anaphylaxis

Repeat challenge with re-evaluation

Figure 9.5  Flowchart for the diagnosis of food-dependent
exercise-induced anaphylaxis. Modified from: Japanese Pediatric
Guideline for Oral Food Challenge Test in Food Allergy 2009.
Allergol Int. 2009; 58: 467–74.

identified that measurement of the concentration of
specific IgE antibodies to ω-5 gliadin is more useful
than measuring IgE antibodies to wheat or gluten.14
In food challenge tests for the diagnosis of FDEIA
the reproducibility of the results is not consistent.
If causative foods are not identified by provocation
tests, in our experience this diagnostic procedure
may need to be repeated (Fig. 9.5). NSAIDs are
known to enhance the symptoms of FDEIA.15 In the
Japanese Pediatric Guideline for Oral Food Challenge
Test in Food Allergy 2009, the flowchart for the diagnosis of FDEIA includes an aspirin challenge prior
to food plus exercise challenge, if the patients do
not react to the suspected foods during the regular
challenge procedure (Fig. 9.5).

Treatment/management
Treatment and management of food-induced anaphylaxis or FDEIA can be subdivided into acute

9

(pharmacological management followed by careful
observation) and long-term. Long-term management consists of the measures that provide the best
quality of life for the patient.

Pharmacological
Most of the treatments for anaphylaxis currently
used are based on consensus rather than highquality evidence. Due in part to the difficulty
in performing well-designed randomized control
trials, few evidence-based studies have so far been
published in this field. Furthermore, according to
Cochrane Review findings, there is insufficient evidence to support the use of adrenaline, antihistamines (H1 agonists) and glucocorticosteroids in the
treatment of anaphylaxis. However, intramuscular
epinephrine has relatively few side-effects in anaphylaxis and is acknowledged as the first line of
therapy both in hospital and in the community.4,8,10,16 An example of a protocol for the initial
management of anaphylaxis in the hospital setting
is shown in Figure 9.6.16

Epinephrine (adrenaline)
Epinephrine should be administered to all patients
with an anaphylactic reaction involving any respiratory and/or cardiovascular symptoms or signs.
However, acute management should be tailored
to the individual. For example, if a patient has
recurrent episodes of anaphylaxis commencing
with severe abdominal pain, the earlier use of
epinephrine would be justified if they developed
severe abdominal pain after a subsequent ingestion
of the same allergen. Also, an earlier use of epinephrine is justified in patients with a history of
asthma, particularly in those needing regular
asthma medication.
In general, the same indications apply for
patients and carers as for physicians. Families
finding it difficult to identify early symptoms and
signs of severity should be told to administer epinephrine without waiting for severe symptoms to
develop, as delayed treatment has been associated
with fatalities. Unfortunately, many patients and
carers do not use epinephrine, even when patients
have previously experienced a life-threatening anaphylactic reaction.
The intramuscular route is preferred initially
in all settings because intramuscular epinephrine

123

Food Allergy

EVALUATE
Airway, Breathing and Circulation
Cardio-respiratory arrest

• If possible,
remove allergen
• Call for help

Respiratory distress, hypotension or collapse
GIVE I.M. EPINEPHRINE
Consider lower threshold to treatment with adrenaline if:
• Previous severe reaction
• Exposure to known/likely allergen
• Coexistent asthma

Treat as per protocol
Intramuscular adrenaline dose
0.01 mL/kg epinephrine 1:1000
or
• <10kg: 1:1000 epinephrine,
0.01 mL/kg
• 10–30 kg: self-injectable device
(0.15 mg)
• ≥30 kg: self-injectable device
(0.3 mg)
Observation:
Children with respiratory symptoms
or signs should be observed for at
least 6–8 hours in hospital prior to
discharge. Those presenting with
anaphylactic reactions with
hypotension or collapse should be
observed for at least 24 hours in a
high dependency area or intensive
care unit

Hypotension or
collapse:
• High flow oxygen
• Normal saline or colloid,
20 mL/kg I.V./I.O.
• I.V./I.O. corticosteroid
• I.V./I.O./I.M.
antihistamine
If no response in 5–10
minutes:
• Repeat I.M. adrenaline
• Repeat fluid bolus
• Set up adrenaline I.V.
(infusion)

Discharge check list:
1. Provision of self-injectable epinephrine device with written
instructions on how to administer it correctly
2. Discharge therapy: antihistamine and prednisone (1–2 mg/kg)
for 72 hours
3. Discharge letter for the family doctor
4. Priority access to the allergist for the allergy diagnosis and
the provision of the individualized management plan

Stridor
• High flow oxygen
• Nebulized epinephrine

Wheeze
• High flow oxygen
• Nebulized beta-2agonist

If respiratory distress
or no response within
5–10 minutes:
• I.M. epinephrine
• Nebulized
corticosteroid
• I.V. access

If respiratory distress
or no response within
5–10 minutes:
• I.M. epinephrine
• I.V. access

If no response within
5–10 minutes:
• Repeat nebulized
epinephrine
• Consider further I.M.
epinephrine
• I.V./I.O. corticosteroid
• I.V./I.O./I.M.
antihistamine

If no response within
5–10 minutes:
• Repeat nebulized
beta-2-agonist
• Consider further I.M.
epinephrine
• Consider I.V. beta-2agonist
• I.V./I.O. corticosteroid
• I.V./I.O./I.M.
antihistamine

Angioedema or
urticaria ONLY
• Antihistamine orally
• If known to be
asthmatic give inhaled
beta-2-agonist and oral
prednisolone
• Observe for 4 hours
– as this may be an
early presentation of
anaphylaxis
PLUS
Persistent vomiting
and/or
abdominal pain
– CONSIDER
I.M. adrenaline

Figure 9.6  An example of a protocol for the initial management of anaphylaxis in the emergency department. Muraro A, Roberts G,
Clark A, et al. The management of anaphylaxis in childhood: position paper of the European academy of allergology and clinical
immunology. Allergy. 2007 Aug; 62(8): 857–71.

is rapidly bioavailable, with peak concentrations
occurring within 10 minutes of administration, and
has a much better safety profile and longer-lasting
action than intravenous adrenaline. The recommended site for self-injectable epinephrine is the
anterior lateral thigh, as there are neither major
arteries nor nerves in that area.
For the intramuscular route, 1 : 1000 epinephrine
(1 mg/mL) should be used at a dose of 0.01 mL/kg
body weight (maximum single dose 0.3–0.5 mg).
This dosage can be repeated at short intervals (every
5–10 min) until the patient’s condition stabilizes.
If intravenous adrenaline is used, a dose of 0.1 µg
/kg/min has been recommended.16
124

Fluid support
Severe episodes of anaphylaxis often involve the
cardiovascular system, resulting in tachycardia and
decreased arterial blood pressure. They should be
treated with both adrenaline and volume support.

Inhaled β2-agonist
A β2-agonist inhaled through a spacer device or
by nebulizer is a useful adjuvant for treating bronchospasm associated with anaphylaxis. However,
these provide treatment only for the broncho­
spasm, whereas anaphylaxis is a systemic disease.
Delivery of β2-agonists may be impaired by acute

Food-induced Anaphylaxis and Food Associated Exercise-induced Anaphylaxis

bronchospasm and systemic adrenaline must
always be considered the first-line therapy.

Antihistamine (H1)
Antihistamines (H1 antagonists) should be given
promptly if a patient has been exposed to an allergen
or develops clinical symptoms or signs of an allergic
reaction. However, there is no research-supported
evidence of their efficacy in anaphylaxis.

Glucocorticosteroid
Corticosteroids should not be considered as a firstline treatment for anaphylaxis. They do not act fast
enough and their efficacy in reducing the risk of
late-phase reactions has not been fully proven.

Observation period
There is no consensus in the literature regarding
the optimal period that a patient who has been
successfully treated for anaphylaxis should be
observed prior to discharge from the hospital. All
patients who receive epinephrine for food-induced
anaphylaxis should proceed to an emergency facility for observation and additional treatment if
needed. A reasonable period for observation is 4–6
hours in most patients who have experienced anaphylaxis and have received epinephrine. An overnight hospital stay should be considered for patients
with severe or prolonged symptoms.8,10,16

Long-term management in the
community
Avoidance of causative foods
Patients or parents should be informed of the possibility of a subsequent allergic reaction after ingestion, contact with or inhalation of food allergens.
Patients should be carefully instructed about hidden
allergens, potential cross-reactions to other allergens, and situations that constitute a special hazard
for those with food allergy, such as exposure to
foods at school, daycare, the homes of friends or
relatives and restaurants.9,10,16

Education for specific for FDEIA
The main strategy for the prevention of FDEIA is
avoidance of the causative food allergen for up to
4 hours prior to exercise.5,10

9

Risk management plan
Prior to discharge patients should be given a written
anaphylaxis emergency action plan that contains
information about self-injection of epinephrine.8
An example of an action plan is available at
www.foodallergy.org.

Self-injectable adrenaline
All patients experiencing food-induced anaphylaxis
should be provided directly with an epinephrine
autoinjector, or with a prescription for it, and the
advice to fill it immediately. Several different brands
of device are available in many countries. Current
worldwide availability of devices such as EpiPen,
Anapen and Twinject is summarized in Table 9.9.
A new device, Jext, will be available in European
countries in 2011. Unfortunately, there is no selfinjectable epinephrine device for infants under
15 kg body weight, but mild overdosing with selfinjectable adrenaline in a young child device does
not represent a major risk in otherwise healthy children. The physician should weigh the risk of severe
anaphylaxis over the potential side effects of
adrenaline.

Immunomodulation (oral immunotherapy
for food-induced anaphylaxis)
Primary food-induced anaphylaxis could theoretically be modulated by allergen desensitization
through immunotherapy, similarly to bee sting
anaphylaxis. However, immunotherapy in food
allergy desensitization remains experimental, and
although several trials of oral tolerance induction
are under way, this procedure is not yet recommended in routine clinical practice. Significantly
increased thresholds to food-induced allergic reactions after oral immunotherapy were reported in
almost all of those with milk and egg allergy and
more than 90% of those with peanut allergy. It is
likely that this increased threshold is dependent on
ingestion of the food and reflects desensitization
but not true tolerance. The efficacy of the immunotherapy, extent of desensitization versus tolerance,
and the quantity/frequency of allergen consumption required to maintain this effect are currently
unknown.11
Acknowledgement
The author wishes to thank Ms Chizuko Sugizaki
and Dr Sakura Sato for their support in the writing
of this chapter.
125

Food Allergy
Table 9.9  Adrenaline auto-injector worldwide availability

Area
Europe

Country

EpiPen/Fastjekt

Anapen

Austria

O

O

Germany

O

O

Hungary

O

O

Netherlands

O

O

Poland

O

O

Portugal

O

O

Sweden

O

O

Switzerland

O

O

Belgium

O

Czech Republic

O

Denmark

O

Finland

O

Italy

O

Luxemburg

O

Norway

O

Slovakia

O

Slovenia

O

Spain

O

UK

O

France

O

Greece
North America
South America
Africa and Middle East
Asia

Oceania

126

Twinject

O

USA

O

Canada

O

Argentina

O

Chile

O

Israel

O

South Africa

O

Japan

O

Malaysia

O

Singapore

O

Thailand

O

Australia

O

New Zealand

O

O

O

Food-induced Anaphylaxis and Food Associated Exercise-induced Anaphylaxis

References
1. Metcalfe DD, Sampson HA, Simon RA. Food Allergy:
Adverse Reactions to Foods and Food Additives. 4th ed.
Blackwell Publishing, 2008.
2. Maulitz RM, Pratt DS, Schocket AL. Exercise-induced
anaphylactic reaction to shellfish. J Allergy Clin
Immunol 1979;63(6):433–4.
3. Sampson HA, Muñoz-Furlong A, Campbell RL, et al.
Second symposium on the definition and management
of anaphylaxis: summary report – Second National
Institute of Allergy and Infectious Disease/Food Allergy
and Anaphylaxis Network symposium. J Allergy Clin
Immunol 2006;117(2):391–7.
4. Sampson HA. Anaphylaxis and emergency treatment.
Pediatrics 2003;111(6 Pt 3):1601–8.
5. Du Toit G. Food-dependent exercise-induced
anaphylaxis in childhood. Pediatr Allergy Immunol
2007;18(5):455–63.
6. Aihara Y, Takahashi Y, Kotoyori T, et al. Frequency of
food-dependent, exercise-induced anaphylaxis in
Japanese junior-high-school students. J Allergy Clin
Immunol 2001;108(6):1035–9.
7. Aihara Y. [Food-dependent exercise-induced
anaphylaxis]. Arerugi 2007;56(5):451–6.
8. Simons FE. Anaphylaxis: Recent advances in assessment
and treatment. J Allergy Clin Immunol 2009;
124(4):625–36; quiz 637–8.
9. Sicherer SH, Sampson HA. Food allergy. J Allergy Clin
Immunol 2010;125(2 Suppl. 2):S116–25.

9

10. Ebisawa M. Management of food allergy in Japan
‘food allergy management guideline 2008 (revision
from 2005)’ and ‘guidelines for the treatment of
allergic diseases in schools’. Allergol Int 2009;
58(4):475–83.
11. Ben-Shoshan M, Clarke AE. Anaphylaxis: past, present
and future. Allergy 2011;66(1):1–14.
12. Inomata N, Osuna H, Ikezawa Z. Late-onset
anaphylaxis to Bacillus natto-fermented soybeans
(natto). J Allergy Clin Immunol 2004;113(5):
998–1000.
13. Commins SP, Satinover SM, Hosen J, et al. Delayed
anaphylaxis, angioedema, or urticaria after
consumption of red meat in patients with IgE
antibodies specific for galactose-alpha-1,3-galactose. J
Allergy Clin Immunol 2009;123(2):426–33.
14. Matsuo H, Dahlström J, Tanaka A, et al. Sensitivity and
specificity of recombinant omega-5 gliadin-specific IgE
measurement for the diagnosis of wheat-dependent
exercise-induced anaphylaxis. Allergy 2008;
63(2):233–6.
15. Shirai T, Matsui T, Uto T, et al. Nonsteroidal antiinflammatory drugs enhance allergic reactions in a
patient with wheat-induced anaphylaxis. Allergy
2003;58(10):1071.
16. Muraro A, Roberts G, Clark A, et al. The management
of anaphylaxis in childhood: position paper of the
European academy of allergology and clinical
immunology. Allergy 2007;
62(8):857–71.

127

CHAPTER

10 

Eosinophilic Gastroenteropathies
(Eosinophilic Esophagitis, Eosinophilic
Gastroenteritis and Eosinophilic Colitis)
Dan Atkins and Glenn T. Furuta

KEY CONCEPTS
Mucosal eosinophilia is an increasingly common
diagnostic finding that must be interpreted in the
appropriate clinical context.
 Eosinophilic esophagitis (EoE) is a clinicopathological
disease characterized by reflux-like symptoms, feeding
difficulties, food impaction and dysphagia in the setting
of dense esophageal eosinophilia (>15 eosinophils/hpf).
 Pathophysiological mechanisms of EoE relate to the
food/environmental induction of epithelial eotaxin-3


Eosinophilic gastrointestinal
diseases (EGIDs)
The emergence of eosinophilic esophagitis as an
increasingly encountered entity among allergists
and gastroenterologists has generated a renewed
interest in the role of eosinophils, not only in the
esophagus where they are normally absent, but also
in other areas of the gastrointestinal tract, including
the stomach and small and large intestine, where
they normally reside in benign numbers. Gastroenterologists encounter eosinophilic gastrointestinal
diseases (EGIDs) as a result of the endoscopic evaluation of patients presenting with a variety of
common gastrointestinal complaints, whereas the
allergist often sees them as they present to discern
whether food allergies are the cause of their discomfort. EGIDs have significantly increased the
interplay between gastroenterologists and allergists,
© 2012, Elsevier Inc

overexpression, which leads to chronic inflammation
with a predominant mucosal eosinophilia.
 Treatment of EoE is directed at either nutritional
exclusion of suspected food allergens or the application
of topical steroid to the esophageal mucosa.
 Eosinophilic gastroenteritis can affect the mucosa,
muscular or serosal layers of the gastrointestinal tract.

as eosinophils are often considered the harbinger
of allergic disease and an increasing body of clinical
and research evidence suggests that many of these
patients are indeed allergic.1
To date, the exact clinicopathological features
that define EGIDs remain under deliberation.2
Because eosinophils are normal inhabitants of the
GI tract other than the esophagus, the definition of
what constitutes normal or abnormal is contingent
upon a number of different factors3–6 (Table 10.1).
When the degree of eosinophilic infiltrate is deemed
excessive, the relevance of this finding must be
interpreted in the clinical context of why the biopsy
was obtained, as mucosal eosinophilia can be associated with a number of different diseases, including inflammatory bowel diseases, infections and
allergic inflammatory responses.
When other diseases associated with mucosal
eosinophilia have been excluded, the diagnosis
of EGIDs is assigned. EGIDs can be subdivided

Food Allergy
Table 10.1  Etiologies for intestinal eosinophilia

Esophagus

Small intestine and colon

Gastroesophageal reflux disease
Eosinophilic esophagitis
Eosinophilic gastroenteritis
Crohn’s disease
Connective tissue disease
Hypereosinophilic syndrome
Infectious: Candida, herpes virus
Drug hypersensitivity response

Food hypersensitivity
Eosinophilic gastroenteritis
Inflammatory bowel disease
Celiac disease
Infectious: Ancylostoma duodenale, anisakiasis, basidiobolomycosis, Enterobius
vermicularis, Helicobacter pylori, schistosomiasis, Toxocara canis,
Malignancy
Churg–Strauss syndrome
Systemic lupus erythematosus

Table 10.2  Symptoms associated with eosinophilic esophagitis

Children

Adolescent and adult

Abdominal pain
Feeding difficulty
Reflux symptoms unresponsive to medical/surgical management
Esophageal food or foreign body impaction

Dysphagia
Reflux symptoms unresponsive to medical/
surgical management
Esophageal food or foreign body impaction

according to the area of the GI tract involved.
Eosinophilic esophagitis affects only the esophagus, whereas eosinophilic colitis affects only the
colon and eosinophilic gastroenteritis can affect
multiple parts of the GI tract. These distinctions
are important, as pathophysiological mechanisms,
natural history and therapeutic interventions can
differ between EGIDs. This chapter will focus on
clinical features, the role of allergy and therapeutic
interventions for EGIDs, with a special emphasis on
the most common EGID, eosinophilic esophagitis
(EoE).

Eosinophilic esophagitis
Clinical features/diagnosis
Originally a clinical curiosity, increasing clinical
experience and research studies have transformed eosinophilic esophagitis (EoE) into a
well-characterized
clinicopathological
entity.7
Multidisciplinary diagnostic and therapeutic recommendations for EoE were developed at the First
International Gastrointestinal Eosinophil Research
Symposium at Orlando, Florida, in October 2006
(www.naspghan.org for slide set of program). At
the time of this process, EoE was characterized as a
clinicopathological disease requiring symptoms
and isolated esophageal eosinophilia manifested
130

by a minimum of 15 intraepithelial eosinophils in
the most densely involved high-power microscopic
field (400×). Because of its significant prevalence,
gastroesophageal reflux disease (GERD) should be
ruled out as a potential cause for esophageal eosinophilia with either a trial of proton pump inhibition or pH/impedance monitoring of the distal
esophagus before the diagnosis of EoE is made.8,9
A number of different names have been associated with eosinophilic esophagitis, including
eosinophilic oesophagitis, primary eosinophilic
esophagitis, allergic eosinophilic esophagitis and
idiopathic eosinophilic esophagitis. Although some
still refer to eosinophilic esophagitis as EE, EoE has
been increasingly used by gastroenterologists to
avoid confusion because of the historical use of EE
to refer to erosive esophagitis. As a result, EoE will
be used here.
EoE in children has several different patterns of
clinical presentation (Table 10.2). Infants or toddlers may present with feeding difficulties,10–14
which may manifest as feeding refusal or problems
with advancing the diet to include a broader array
of new textures (see Clinical Case 1). Other children may complain of GERD-like symptoms unresponsive to acid blockade.14–16 Symptoms can
include vomiting, regurgitation, waterbrash, epigastric abdominal pain, heartburn or chest pain. Older

Eosinophilic Gastroenteropathies

children, teenagers and adults may develop intermittent or chronic dysphagia or present acutely
with food impaction.

CLINICAL CASE 1
AT is a 3-year-old boy brought for evaluation of
inadequate growth. His mother reports that he had
gastroesophageal reflux as an infant that resolved at 1
year of age, but since then he has been difficult to feed.
Initially, he would put food in his mouth but not swallow
it. More recently, he has refused to eat most foods and
prefers only soft foods and liquids. His pediatrician reports
that over the last 6 months his weight has dropped from
the 35th percentile to the 10th. His physical examination is
unremarkable except for eczema. Initial laboratory testing
is normal. Nutritional evaluation reveals that he is not
meeting his caloric needs. Two months of taking
lansoprazole did not alter his growth pattern or eating
preferences. An upper endoscopy revealed white exudates
on his esophageal mucosa, and 33 eosinophils/hpf in the
esophageal epithelia with normal gastric and duodenal
biopsies. Serum food-specific IgE levels and skin prick tests
to foods he was eating revealed sensitization to wheat and
eggs, so these foods were removed from his diet. He was
evaluated and treated by a feeding specialist. Over the
course of the next 6 months, his appetite and eating
behaviors normalized and his weight began to follow the
30th percentile.
Toddlers with EoE may present with feeding difficulties
and behaviors that at a minimum lead to family unrest at
mealtimes and in some circumstances result in growth
disturbances. Even after inflammation has resolved as a
result of appropriate elimination diets and/or other
therapies, feeding dysfunction can persist and may require
the expertise of a feeding specialist.

The most common presentation of recalcitrant
GERD-like symptoms was first documented through
a unique collaboration between allergists and gastroenterologists over 15 years ago, when Kelly
and colleagues reported 10 patients with severe
GERD, six of whom remained symptomatic despite
fundoplication.17 These patients developed clinicopathological remission when placed on an elemental formula and symptoms returned upon food
challenge. Orenstein’s18 detailed analysis of 30
children with esophageal eosinophilia identified
vomiting, abdominal pain and dysphagia as the
most common associated symptoms. Over 60% of
the patients had concomitant asthma, recurrent
upper respiratory illnesses and pneumonias, suggesting an association of EoE with other allergic
and/or airway diseases. Liacouras et al.15 described
their findings in one of the largest pediatric series
of 381 children with EoE, of whom over 300 had

10

GERD-like symptoms while 69 presented with
dysphagia.
EoE also commonly presents with an isolated
esophageal food impaction that is thought to occur
secondary to either a fixed anatomical stricture or
intermittent esophageal spasm19–24 (see Clinical
Case 2). Studies in both adults and children have
documented that EoE is a common etiology for
esophageal food impaction. For instance, Desai19
reported that 17 of 31 adult patients presenting
with an acute esophageal food impaction had > 20
eosinophils per hpf.
Recalcitrant GERD-like symptoms, dysphagia
and food impaction, especially when encountered
in patients with other atopic diseases, should raise
the suspicion for EoE (see Clinical Case 3).

CLINICAL CASE 2
TL is a 15-year-old boy who was seen in the emergency
room for food impaction. He had been on a hunting trip in
the mountains when he ate turkey jerky that became
lodged in his esophagus, preventing him from being able
to swallow his saliva. He did not experience respiratory
distress. A detailed history of his eating habits revealed
that he always drank three to four glasses of water during
meals to wash his food down. Typically he avoided meats
because they were difficult to swallow, but he enjoyed
eating jerky, particularly while hunting. Endoscopic
analysis revealed that his proximal esophagus was
obstructed by a food bolus that was removed. Distal to the
bolus an esophageal stricture was identified and mucosal
biopsies were obtained that revealed >15 eosinophils/hpf
in the squamous epithelium. He was started on
omeprazole 2 mg/kg/day and returned for esophageal
dilation. Mucosal eosinophilia persisted and he was
treated with topical fluticasone (220 µg) two puffs sprayed
into the back of his throat and swallowed twice a day,
without brushing his teeth or eating or drinking for 30
minutes afterward. He declined food allergy testing and
was symptom free on swallowed fluticasone alone.
The long-term use of complex coping behaviors related to
eating is surprisingly common in adolescents with EoE, for
example avoiding densely textured foods such as meats,
eating slower than others, using sauces as lubricants, and
drinking large amounts of liquids during meals. In these
patients an acute presentation with food impaction is
unpredictable, often leading to diagnostic and therapeutic
endoscopy and esophageal dilation. Proximal esophageal
strictures are highly unusual and can result from caustic
ingestions, surgical procedures, congenital anomalies or
EoE. Not all food impactions are related to esophageal
strictures: some patients may have a non-obstructive
mucosa where the impaction is thought to result from
transient esophageal contractions. Whether the inciting
foods are the allergic trigger for these presentations is
unknown.
131

Food Allergy

CLINICAL CASE 3
HE is an 18-year-old boy with a 4-year history of dysphagia
and heartburn. Use of over-the-counter antacid treatments
did not provide adequate relief of his symptoms. Over the
course of the last year his dysphagia has increased to the
point that he was unable to swallow solid foods without
pounding on his chest and drinking copious amounts
of liquids. This led to social embarrassment, and he
frequently eats alone because it takes him so long to
complete a meal. He also has mild eczema and allergic
rhinitis. When he takes fluticasone for his asthma and
allergic rhinitis, his swallowing improves slightly.
Endoscopic analysis when he is not taking any topical
steroid preparations reveals 51 eosinophils/hpf and a pH/
impedance monitoring study of his distal esophagus is
normal. A diagnosis of EoE was made and subsequent
food allergy testing revealed positive skin tests to cows’
milk and soy. Upon elimination of these foods his
symptoms resolved, and re-examination of his esophageal
mucosa revealed complete resolution of inflammation.
This case illustrates a number of clinical clues for the
diagnosis of EoE. EoE is more common in boys, with over
75% of patients being male. A long-standing history of
dysphagia, especially in a patient with an atopic
background, is often found. Partial clinical responses to
topical steroids used for treatment of asthma and allergic
rhinitis also support further evaluation because a portion
of these preparations are swallowed and may
inadvertently reduce esophageal inflammation. Since
gastroesophageal reflux is more common than EoE, and
can present with a similar clinical and histological pattern,
GERD should be ruled out in all patients in whom EoE is
considered. Skin testing can reveal food sensitivities that
often identify the allergen(s) inciting EoE.

Epidemiology
Over 75% of patients with EoE are male. EoE occurs
at any age without obvious predilection, and has
been reported on all continents except Africa. Noel
estimated a disease incidence of ~1 : 10 000 children per year in Ohio, USA, and Straumann estimated an increase from 2 to 27 per 100 000 adults
in Olten, Switzerland.25,26

Pathophysiology
Basic studies provide a link between fibrotic
cascades and eosinophil-derived mediators. Eosinophils contain mediators capable of both indu­
cing fibrotic molecules such as TGF-β and
stimulating tissue contraction such as major basic
protein. Aceves27 provided translational evidence
supportive of a fibrotic pattern in affected children.
In this study, five patients with EoE and evidence
of fibrosis were compared to two with non-fibrotic
132

EoE, seven with GERD and seven normal patients.
Patients with fibrotic EoE showed increased subepithelial fibrosis, TGF-β, VCAM-1 and phosphoSMAD2/3 expression compared to GERD and
normal control patients. During a 14-year follow-up
in adult patients with EoE, esophageal cancer has
not been reported.28
Patterns of genetic influence on EoE are emerging. Zink29 reported 17 patients from seven families
with dysphagia and gastrointestinal eosinophilia.
Of these, 12 patients spanning two generations
were shown to have EoE. Patel30 described three
brothers with intermittent dysphagia and 20–40
eosinophils per hpf in the esophageal epithelium.
In a case report, Meyers31 documented an 80-yearold man and his 52-year-old daughter who both
had dysphagia and >40 esophageal eosinophils/
hpf. Thus, increasing clinical experience and case
descriptions suggest a familial pattern and genetic
predisposition.
Blanchard32 hypothesized that a genetic profile
existed for patients with EoE. Microarray analysis
of esophageal tissues from patients with EoE and
GERD identified a unique EoE gene signature,
with the most upregulated gene being eotaxin-3.
Eotaxin-3 levels correlated with mucosal eosinophilia and a single nucleotide polymorphism
suggested susceptibility to EoE. The results of this
study, and that of Mishra, emphasize the potential
for novel therapeutic targets such as CCR-3 receptor
or IL-5 antagonist, for selected patients with EoE.33,34
Using gene array analysis, recent studies determined the potential role of filaggrin, mast cells and
thymic stromal lymphopoetin in the pathogenesis
of EoE.35–37
The esophageal mucosa affected by EoE has
undergone further molecular characterization.
Straumann38,39determined that the esophageal eosinophils from EoE patients expressed increased IL-4
and IL-13 compared to normal controls, and
Gupta40 found that esophageal mRNA expression
in 11 patients with EoE expressed more IFN-γ,
eotaxin-1 and IL-5 than in normal children. Initial
reports have been followed by a number of studies
to determine the impact of these and other
cytokines, including IL-13 and IL-15.41–43

Radiology
Interestingly some of the first EoE reports originated in the radiology literature (Table 10.3).
Picus44 described a 16-year-old boy with increasing

Eosinophilic Gastroenteropathies

Table 10.3  Radiological signs observed in EoE

Table 10.5  Histological features of EoE

Strictures: proximal, middle and/or distal
Longitudinal narrowing
Small caliber esophagus
Esophageal polyp or diverticulum
Concentric rings
Schatzki ring

Mucosal eosinophilia and degranulation
Eosinophil microabscesses
Superficial accumulation of eosinophils
Basal zone hyperplasia
Lymphocytosis
Mast cell accumulation

Table 10.4  Endoscopic findings seen in EoE
White exudates
Esophageal strictures
Concentric rings, trachealization, feline esophagus
Vertical lines of the esophageal mucosa
Crepe paper mucosa/linear shearing of mucosa

dysphagia, proximal esophageal narrowing, eso­
phageal eosinophilia and peripheral eosinophilia
who underwent remission when treated with systemic corticosteroids. Feczko45 described three
adults with dysphagia, allergic diseases, proximal
esophageal strictures and eosinophilic esophageal
inflammation that required both dilation and corticosteroid treatments. Nurko46 reported the association of Schatzki ring and EoE in a 12-year
retrospective review. Of 18 children with Schatzki
ring, eight were found to have clinicopathological
features consistent with EoE. Thus, any esophageal
nar­rowing, especially proximal esophageal strictures, should raise suspicion for the diagnosis of
EoE (see Case 2).

Endoscopy
Although the early literature suggests that endoscopic appearances may be normal in EoE, increased
recognition of the disease documents a number of
mucosal findings, including concentric ring formation (trachealization); longitudinal linear furrows
or vertical lines on the esophageal mucosa; patches
of small, white papules on the esophageal surface;
and esophageal strictures (Table 10.4). Whitish
granular patterns on the mucosa were traditionally
thought to be associated only with Candida infection, but this finding is now also recognized as
evidence of eosinophilic inflammation. Sundaram47 reported that the esophageal epithelium of
13 children with EoE had white specks representing

10

an underlying epithelium containing 25–100 eosinophils per hpf without fungal elements. In a later
report, Straumann,48 in an analysis of 30 adults
with EoE, showed that white exudates were consistent with eosinophilic inflammation. In contrast,
Ngo49 reported a child with clinicopathological features of EoE, including white exudates and large
numbers of eosinophils in the squamous epithelium, who responded to proton pump inhibition.
Thus, if white material is reported on the esophageal mucosa, peptic disease, Candida infection and
EoE should be diagnostic considerations.

Histology
It is unusual that the number of a specific cell type
is critical to the diagnosis of an inflammatory
disease (Table 10.5). To date, the diagnosis of EoE
rests on the finding of a dense eosinophilic inflammation of the esophageal epithelium in the proper
clinical setting.3 The ideal density has been the
subject of much discussion and consists of a threshold ranging from 15 to 24 eosinophils per hpf.
Variables affecting this number include size of
the high-power field, characterization of the eosinophils observed, and the number of high-power
fields considered.50,51
Another finding supporting a diagnosis of EoE is
eosinophil activation as evidenced by degranulation. Mueller52,53 reported that specific staining for
eosinophil granule-derived major basic protein
(MBP) significantly enhanced eosinophil visualization in adults with EoE. Desai19 showed that extracellular MBP deposition significantly distinguished
adults with EoE from those with GERD. Protheroe54
demonstrated the impact of a novel scoring system
that used antibody staining for eosinophil peroxidase (EPX) in the analysis of the epithelia in EoE.
In this study, EPX scoring was able to separate
patients with EoE from those with GERD and
normal controls to a significant degree. Similar
133

Food Allergy

findings were reported in another recent study.55
Despite these studies, it is important to note that
eosinophil degranulation can occur during biopsy
procurement and processing. Lymphocytic inflammation occurs more significantly in EoE patients
than in those with GERD. In addition, mast cell
infiltration and activation is more common in EoE
than in patients with GERD.
To date, the only documented long-term complication associated with EoE is isolated or long
segment esophageal narrowing. Adult and pediatric
reports have identified evidence of tissue remodel­
ing in the form of proximal and distal esophageal
strictures. Typically, symptoms in these patients
date back to childhood, suggesting that the development of lesions requires decades of persistent or
intermittent inflammation.

Role of allergy
Allergic manifestations
Several lines of indirect and direct evidence support
a likely role for allergic inflammation in EoE. Eosinophils are commonly observed in the mucosal
surfaces in asthma, allergic rhinitis and eczema. An
increasing number of studies associate EoE with
comorbid IgE-mediated allergic disease such as
food allergy, eczema, allergic rhinitis and asthma,
including two that demonstrate the potential
role of aeroallergens in EoE. In line with the findings of genome-wide association studies (GWAS), a
family history of EoE in affected children is not
uncommon.
The direct application of foods to the esophageal
mucosa, along with an increasing amount of clinical experience and research, supports a causative
role for food allergy in EoE. Food allergies coexist
in up to 73% of children with EoE. Food allergens
including milk, egg, wheat, soy, peanuts, beans, rye
and beef are most often identified during skin
testing, but a number of other foods may play a role
as well. In addition, allergic sensitization to more
than one food occurs frequently. When examining
compiled case series of 786 EoE patients in whom
larger panels of food skin tests were applied, the
mean number of identified food allergens varied
from 2.7 ± 3.3 to 6 ± 4.2. In adults, patterns may
differ both in range of sensitization and patterns of
suspected foods, perhaps reflecting cross-reactivity
among foods and inhaled pollen allergens, a
common finding in patients with EoE. Case reports
have correlated pollen skin test results and seasonal
134

changes in symptoms and numbers of mucosal
esophageal eosinophils. Thus, pollen sensitization
could potentially promote esophageal mucosal
eosinophilia either through direct exposure to
pollen swallowed after inhalation during the pollen
season or by the ingestion of plant-derived foods
that contain cross-reacting allergens. For example,
a ragweed-allergic EoE patient could potentially
experience an increase in symptoms in the fall
during the ragweed pollen season, or after ingesting
bananas or melons that contain allergens crossreacting with those found in ragweed pollen.
Immune mechanisms underlying food allergic
reactions are categorized as IgE-mediated, non-IgEmediated or combined. IgE-mediated food allergies
occur when a genetically predisposed host is
exposed to a food leading to the generation of
allergen-specific IgE. This IgE binds to and occupies
high-affinity IgE receptors on mast cell and basophil
cell surface membranes, resulting in sensitization.
Upon re-exposure to this food, cell surface allergenspecific IgE molecules cross-link, thereby bridging
their high-affinity receptors with subsequent release
of preformed and newly synthesized mediators,
some of which are eosinophil chemoattractants.
Translational studies support the presence of
increased IgE-bearing mast cells in the epithelia of
patients with EoE, but in addition to IgE-mediated
responses, non-IgE-mediated immune mechanisms
are also considered to be involved in the pathophysiology of EoE. Careful histories for symptoms
suggestive of IgE-mediated reactions should be
taken, as EoE patients may have comorbid IgEmediated reactions to foods; discussions focusing
on avoidance of these foods and treatment of anaphylactic reactions resulting from accidental exposure are warranted.
Typically, non-IgE-mediated reactions coordinated by Th2 lymphocytes are slower in onset,
evolve over hours to days, and can result in mucosal
eosinophil accumulation. This delay in symptom
onset complicates accurate identification of offending foods in non-IgE-mediated food allergy. EoE
symptoms are often consistent with those seen in
non-IgE-mediated reactions in that they are localized to the gastrointestinal tract and can be delayed
rather than immediate in onset.
Because EoE is considered a combined disorder
involving both IgE- and non-IgE-mediated immune
mechanisms, suggested methods to document
sensitization to foods after obtaining a thorough
history include skin prick testing, measurement of

Eosinophilic Gastroenteropathies

serum food allergen-specific IgE antibodies and
atopy patch testing. Skin prick testing is essentially
a bioassay performed by introducing minute
amounts of allergen into the epidermis and monitoring for a localized cutaneous allergic reaction. If
mast cells in the patient’s skin have IgE on their
surface specific for the allergen being tested, binding
to these IgE antibodies by the allergen triggers mast
cell degranulation, accompanied by histamine
release and mediator generation resulting in the
rapid formation of a cutaneous wheal surrounded
by an erythematous flare. In the absence of IgE
specific for the allergen, no reaction occurs. Glycerinated commercial food extracts are widely available for skin testing to many common food
allergens. In addition, fresh food extracts, prepared
by crushing the food in an aliquot of saline, are
occasionally used.56 Alternatively, the ‘prick-toprick’ technique, which involves pricking a food
such as a fruit or vegetable with the skin test device,
followed immediately by pricking the patient’s
skin, can be used.57 Fresh extract testing can be
useful when testing for sensitivity to fruits or vegetables containing labile allergens susceptible to
degradation during the extraction process used in
the preparation of commercial extracts, or when a
commercial extract of the suspected food is unavailable. The potential for irritant reactions can be
ruled out when necessary by skin testing others not
sensitive to the food using the same extract. After
pricking the skin of the back or arm with a disposable bifurcated skin test device that introduces a
small amount of allergen, any resultant wheal and
erythema observed at the site after approximately
15 minutes is recorded. A histamine skin test is
applied as a positive control with a saline skin test
serving as the negative control. A skin test is considered positive if a wheal 3 mm larger than the
negative control is observed. Skin testing to all or
at least the majority of foods in the patient’s diet is
encouraged when evaluating patients with EoE to
ensure that all foods to which the patient could
potentially react have been identified. In addition,
skin testing to environmental allergens is beneficial
because of the potential for aeroallergens to affect
esophageal inflammation, either through direct
exposure or through cross-reactivity with certain
plant-derived foods in the diet. Benefits of skin
testing include the relatively low cost, immediate
results, and the relatively high negative predictive
accuracy. However, commercial food extracts
and fresh food extracts are not standardized. In

10

addition, the positive predictive accuracy of skin
testing is considered to be relatively low, meaning
that some patients with a positive skin test are sensitized but not allergic, and would not react clinically upon exposure to the food. Alternatively,
given that exposure to the esophageal mucosa
occurs as the food is swallowed, without further
digestion or processing, topical reactions observed
in skin testing might theoretically be more predictive of reactions in EoE than in classic food allergy.
These considerations occasionally increase the difficulty of interpreting skin test results in patients
with EoE. The positive and negative predictive accuracies of skin testing to selected foods in patients
with EoE has been reported by Spergel.58
In addition to skin testing, the level of serum
food-specific IgE can be measured to document IgEmediated sensitivity to a particular food. These
assays are useful when medications that affect skin
testing cannot be discontinued or when widespread
skin disease is present, precluding the use of skin
testing. Measuring serum food-specific IgE levels to
a particular food longitudinally may provide evidence that sensitization to a food is increasing or
waning. In classic IgE-mediated food allergy clinical
studies have identified serum food-specific IgE
levels to selected common food allergens above
which most patients would react.59 Studies to determine corresponding IgE levels for selected foods in
populations of patients with EoE have not been
performed.
In an effort to identify a test that might predict
non-IgE-mediated reactions, the use of the atopy
patch test (APT) in the evaluation of patients with
EoE has been explored.58,59 The APT is performed
by applying the intact food allergen to non-inflamed
skin on the back under occlusion in a small aluminum cup. After 48 hours the patch test is removed
and the resulting reaction is assessed and recorded,
initially at 20 minutes and again at 24 hours after
patch removal. The reactions are graded based on
the degree of erythema and the presence of papules
or vesicles. Although side effects are uncommon,
irritant reactions and contact urticaria have been
reported.60 Other aspects that have hindered widespread use of the APT include lack of standardization of the procedure, including standardized
reagents, in addition to the time and expertise
required for the accurate performance of the test.60
However, Spergel and others58 have reported success
using a combination of skin prick testing and atopy
patch testing to identify foods best eliminated from
135

Food Allergy

the diet, as evidenced by improvement in patients
placed on diets based on the results of this approach.
The most supportive evidence for a role for food
allergy in EoE arises from the multiple observations
and clinical studies that demonstrate clinicopathological improvement of EoE following the use of
several types of elimination diets. Diets in which
the six most common food allergens are excluded
(dairy products, egg, wheat, soy, peanuts, fish/
shellfish) lead to a clinicopathological response in
74% of patients. Elimination diets based on both
skin prick testing and atopy patch testing results
were effective in the majority of children with EoE.
The use of elemental diets, consisting of amino
acid-based formulas, led to the resolution of symptoms and mucosal eosinophilia in more than 95%
of children with EoE. In spite of these successes,
nutritional management in adults and older children poses challenges with compliance and the
impact on their quality of life.
Because of the association of allergic diseases
with EoE and that allergens probably play a role
in the pathogenesis of EoE, a thorough history
and assessment of comorbid allergic diseases is an
important part of the care of patients. Allergy consultation is indicated not only to aid in identifying,
characterizing and treating comorbid allergic
disease, but also to identify food and environmental allergens that may contribute to esophageal
inflammation.

Treatment/management
Although symptom reduction/resolution remains
a clear therapeutic endpoint, the clinical decision
making with regard to mucosal eosinophilia
remains controversial.61 In practice, clinicians are
wary of performing repeated endoscopies as it is
not certain that persistent eosinophilia has untoward consequences. Alternatively, others are concerned that unresolved eosinophilia will lead to
esophageal strictures and therefore must be repeatedly assessed. Future research is needed to clarify
this issue.
Effective and safe therapeutic approaches to the
treatment of EoE include corticosteroids and nutritional management.

Nutritional management
The rationale for using nutritional management in
EoE is based on the research that supports a role
136

for food allergens in esophageal eosinophilic
inflammation. In this regard, a number of studies
support the use of elemental formulas and elimination of specific foods in EoE treatment. Kelly17
reported the successful use of an amino acid-based
diet in the treatment of EoE. Ten children were
treated for 10 weeks: all underwent clinicopathological remission and redeveloped symptoms when
the diet was extensively liberalized. Two other
studies with larger patient cohorts showed that
more than 92% of children were treated successfully with this approach.62–64 Poor compliance has
led to the use of feeding tubes, and some children
may have behavioral issues associated with this
form of treatment.

Corticosteroids
Corticosteroids are effective in resolving the clinicopathological features in most patients with EoE.
Mechanisms of action for eosinophilic inflammation include induction of eosinophil apoptosis,
downregulation of chemotactic factors and inhibition of proinflammatory mediator synthesis and
release. A limited number of patients require systemic corticosteroids, but most can be treated with
an alternative preparation delivered from a metereddose inhaler (MDI) that allows the medication to
be swallowed and thereby deliver a topical application to the esophageal mucosa. It is thought that
this technique limits systemic circulation of steroids because of reduced absorption and first pass
metabolism.
Liacouras65 reported the impact of systemic corticosteroids in 20 of 21 children who experienced a
significant reduction of symptoms within 7 days.
Faubion66 reported the first use of a metered-dose
inhaler of fluticasone for children with EoE in the
hope of limiting steroid exposure. This novel
method reported the successful impact of spraying
fluticasone from an MDI into the mouth without
inhaling and without the use of a spacer in four
children with EoE. The study used fluticasone
propionate (up to 880 µg/day) or beclomethasone twice a day. Since then, a number of other
studies have demonstrated a positive impact of this
approach on clinicopathological features of EoE.67,68
Konikoff performed a randomized double-blind
placebo-controlled study comparing fluticasone
to placebo in 36 pediatric patients.69 Twice-daily
dosing for 3 months induced remission in 50% of
the fluticasone group. When MDIs are used, patients

Eosinophilic Gastroenteropathies

should spray the MDI in their mouth with their lips
sealed around the device and not eat, drink or rinse
for 30 minutes afterward, in an effort to prevent
loss of the delivered dose. An alternative method of
topical steroid delivery has been recently developed. Aceves70,71 prepared a viscous mixture of
budesonide with sucralose, also termed oral viscous
budesonide (OVB). Both retrospective and prospective studies have shown that children undergo successful clinicopathological remission with OVB.
Corticosteroids resolve acute clinicopathological
features of EoE, but when discontinued, EoE recurs.
Side effects reported to date include dry mouth,
cataracts and esophageal candidiasis.

Others
The use of leukotriene receptor antagonists and
mast cell inhibitors has been reported in small
series but not shown to be effective at pharmacological doses.72 Biologicals, including anti-IL-5 antibodies, have undergone recent study. The rationale
for using these agents relates to basic studies revealing a key role for IL-5 in mucosal esophageal eosinophilia. Studies to date demonstrate a significant
impact on mucosal eosinophilia and a trend toward
symptom improvement.73

Eosinophilic gastroenteritis
Eosinophilic gastroenteritis (EOG) represents a heterogeneous group of rare disorders characterized by
various intestinal symptoms and gastrointestinal
eosinophilia.74 Other reasons for intestinal eosinophilia must be excluded before a diagnosis of
EOG can be made.2 Traditional classification
grouped diseases into three categories, mucosal,
muscular and serosal,75 providing a clinical and
pathophysiological paradigm for patients with
these diseases. Patients with mucosal disease typically have symptoms including nondescript abdominal pain, vomiting, and non-bloody, watery
diarrhea. Symptoms can be quite minor compared
to the associated significantly abnormal laboratory
findings. In some circumstances patients may
present with severe anemia and/or hypoalbuminemia, alone or in combination with mild gastrointestinal complaints. Peripheral eosinophilia is an
inconsistent finding, but other causes, such as
hypereosinophilic syndrome or malignancy, should
be ruled out. Radiological findings include polyps,

10

mucosal edema and ulcers. Endoscopic evaluation
can reveal all of these findings or may appear
normal, but histological analysis reveals dense eosinophilia in the lamina propria (see Clinical Case 4).

CLINICAL CASE 4
LH is an 8-year-old girl with chronic diarrhea and
abdominal pain. She has grown well but frequently
develops cramping, diffuse abdominal pain that is relieved
with the passage of mucousy stools. Symptoms were
reportedly associated with egg ingestion. She had no
coincident systemic symptoms such as joint pain or fevers,
but she had a long-standing history of asthma and
eczema. Further investigations revealed mild peripheral
eosinophilia and flocculation of the small bowel on upper
gastrointestinal series. At endoscopy, her upper and lower
intestinal mucosa appeared normal but histopathology
revealed dense eosinophilia of the lamina propria of the
duodenal mucosa. Skin testing to foods in her diet was
negative, but the removal of eggs from her diet led to a
reduction in her symptoms.
As with EoE, children with other EGIDs may present with
common symptoms and thus escape diagnosis for years.
The ingestion of certain foods may trigger symptoms in
some patients but not all, and the use of topical steroids
or other anti-inflammatory medications may be necessary.
Follow-up of patients with lower tract EGIDs is critical, as
some have later been discovered to have inflammatory
bowel diseases.

When eosinophilia affects the muscular layer,
symptoms associated with obstruction, such as
vomiting and bloating, predominate. These patients
are particularly difficult to diagnose as they may
have normal mucosal biopsies; deeper biopsies
procured at surgery demonstrated eosinophilia of
the muscularis. Thus, in a patient with peripheral
eosinophilia, a history of allergic diseases, no other
identifiable causes for gastrointestinal symptoms
and intestinal thickening on radiological imaging,
along with a response to corticosteroids or dietary
elimination, a provisional diagnosis can be made.
Serosal eosinophilic gastroenteritis is extremely
rare, presenting with abdominal bloating and a
fluid wave on physical examination. A peritoneal
tap of the ascitic fluid reveals eosinophilia.
Pathophysiological mechanisms of eosinophilic
gastroenteritis are still poorly defined. A number of
translational studies have provided immunohistochemical descriptions. For instance, mucosal biopsies from these patients demonstrate deposition of
eosinophil granule proteins and increased expression of IL-5. Chehade76 demonstrated increased
mast cells in the small intestine of children with
severe protein-losing enteropathy and eosinophilic
137

Food Allergy

gastroenteritis. Murine studies identified roles for
eotaxin-1 and Th2 lymphocytes in the pathogenesis
of eosinophilic inflammation.77
Standardized criteria defining the histological
features of eosinophilic gastroenteritis are lacking.
Two studies have documented normal values for
mucosal eosinophils, but no diagnostic guidelines
exist.5,6 Corticosteroids are the primary medical
treatment for eosinophilic gastroenteritis, but controlled trials have not yet been performed. Topical
steroids may be beneficial in small intestinal disease.
Ketotifen, cromolyn and montelukast have been
reported to be helpful in isolated case reports. The
utility of food elimination diets in treating patients
with eosinophilic gastroenteritis is unknown but
may benefit some patients, especially younger
patients who have abnormal skin testing for food
allergens.

Eosinophilic colitis
Eosinophilic colitis can be categorized in a variety
of different ways. For instance, allergic proctitis is a
self-limited inflammatory disease presenting during
infancy as blood-streaked stools in an otherwise
healthy infant. The colonic mucosa contains
increased eosinophils in the lamina propria without
evidence of chronic changes. Milk proteins (cows’,
soy or breast milk) are the usual offending agents,
and upon their removal the blood loss stops. On
the other hand, inflammatory bowel diseases,
Crohn’s disease and ulcerative colitis are chronic
inflammatory diseases that are manifest by abdominal pain, bloody stools, diarrhea, and in some
circumstances malnutrition. Mucosal inflammation is characterized by neutrophilic inflammation
with crypt abscesses and chronic inflammation of
the lamina propria. Eosinophils are increased in the
mucosa but are not the predominant cell type.
Patients require immunosuppression with corticosteroids or other agents to induce remission. Finally,
eosinophilic colitis is a somewhat vague term
describing a histological finding that can occur in a
number of different clinical settings. As a histological finding, eosinophilic inflammation of the
colonic mucosa is characterized by a predominance
of eosinophils in the lamina propria without
chronic features. This can be associated with food
allergies, autoimmune diseases, immunodeficiencies, drug hypersensitivity reactions, infections and

138

eosinophilic gastrointestinal diseases. Thus, this
histological finding must be interpreted in the clinical context in which it was obtained.

Summary
Allergists in practice are increasingly encountering
eosinophilic gastrointestinal diseases. Although
much information has been obtained over the last
decade regarding eosinophilic esophagitis, eosinophilic inflammation of the remainder of the GI
tract has remained relatively understudied. Despite
the fact that diagnostic features of EoE are now
better recognized, specifics of the allergic evaluation and treatment paradigms remain to be elucidated. Longitudinal multicentered studies involving
a number of subspecialists such as pediatric and
adult gastroenterologists, allergists, pathologists
and radiologists will be critical to providing answers
that will ultimately lead to cures and improve the
quality of life of patients with EGIDs.

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76. Chehade M, Magid MS, Mofidi S, et al. Allergic
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141

CHAPTER

11 

Food Protein-Induced Enterocolitis
Syndrome, Food Protein-Induced
Enteropathy, Proctocolitis, and
Infantile Colic
Stephanie Ann Leonard and Anna Nowak-We˛grzyn

KEY CONCEPTS
Food protein-induced enterocolitis syndrome (FPIES),
proctocolitis and enteropathy are non-IgE-mediated
gastrointestinal food allergy disorders which in a
majority of cases resolve by age 3 years.
 FPIES is usually caused by cows’ milk and soy, but may
also be caused by cereal grains (rice, oats and barley),
egg, fish, molluscs, poultry and vegetables.
 Food protein-induced proctocolitis is a benign transient
disorder of infancy considered to be one of the major
causes of rectal bleeding under age 1 year.


Food protein-induced
enterocolitis syndrome
Food protein-induced enterocolitis syndrome
(FPIES) is a non-IgE-mediated gastrointestinal food
hypersensitivity that manifests as profuse vomiting
and diarrhea.1 Although it has been established
as a distinct clinical entity, features of FPIES,
especially the chronic form, overlap with food
protein-induced proctocolitis and enteropathy
(Table 11.1).

Epidemiology
In a large birth cohort conducted in Israel 0.34%
(44/13,019) of infants developed FPIES2. In general,
gastrointestinal immune reactions to cows’ milk
© 2012, Elsevier Inc

Classic infantile food protein-induced enteropathy is
caused by cows’ milk, soy and wheat. Recent reports
describe subtle enteropathy in children with multiple
IgE-mediated food allergies, as well as in older children
and adults with delayed food allergy to cows’ milk and
cereal grains.
 Infantile colic is a benign self-limiting condition which
usually resolves by age 3–4 months. A subset of cases
may be food protein-induced, particularly by cows’ milk
and/or soy.


proteins that are mediated by T lymphocytes with
or without contribution from specific IgE antibody
are estimated to account for up to 40% of milk
protein hypersensitivity in infants and young children.3 A family history of atopy is positive in 40–
80% of patients; family history is positive for food
allergy in about 20% of the cases. Approximately
30% of infants with FPIES develop atopic diseases
such as eczema (23–57%), asthma or rhinitis
(20%) or drug hypersensitivity later in life, similar
to the general population.

Pathogenesis
It is hypothesized that local inflammation caused
by ingestion of food allergens leads to increased
intestinal permeability and fluid shift. However,
baseline antigen absorption is normal and does not

Food Allergy
Table 11.1  Food protein-induced enterocolitis syndrome (FPIES), proctocolitis and enteropathy

FPIES

Proctocolitis

Enteropathy

1 day–1 year

1 day–6 months

Dependent on age of
exposure to antigen;
Cows’ milk and soy up
to 2 years

Most common

Cow’s milk, soy

Cow’s milk, soy

Cow’s milk, soy

Less common

Rice, chicken, turkey, fish, pea

Egg, corn, chocolate

Wheat, egg

Multiple food

>50% both cows’ milk and soy

40% both cows’ milk and soy

Rare

Formula

>50% exclusive
breastfeeding

Formula

Family history of atopy

40–70%

25%

Unknown

Personal history of atopy

30%

22%

22%

Genetics

Unknown

Unknown

Unknown

Emesis

Prominent

No

Intermittent

Diarrhea

Moderate-severe*

No

Moderate

Bloody stools

Moderate-severe*

Moderate

Rare

Edema

Acute, severe

No

Moderate

Shock

15%

No

No

Failure to thrive

Moderate

No

Moderate

Anemia

Moderate

Mild

Moderate

Hypoalbuminemia

Acute

Rare

Moderate

Methemoglobinemia

May be present

No

No

Acidemia

May be present

No

No

Leukocytosis

May be present

No

No

Thrombocytosis

May be present

No

No

Food prick skin test

Negative

Negative

Negative

Serum food-allergen IgE

Negative

Negative

Negative

Total IgE

Normal

Normal

Normal

Peripheral blood
eosinophilia

No

Occasional

No

Villous injury

Patchy, variable

No

Variable, increased
crypt length

Colitis

Prominent

Focal

No

Mucosal erosions

Occasional

Occasional, linear

No

Age at onset

Food proteins implicated

hypersensitivities
Feeding at the time of onset

Atopic background

Symptoms

Laboratory findings

Allergy evaluation

Biopsy findings

*Diarrhea may be present in acute cases and can be severe if chronic

144

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

11

Table 11.1  Food protein-induced enterocolitis syndrome (FPIES), proctocolitis and enteropathy—cont’d

FPIES

Proctocolitis

Enteropathy

Lymph. nodular hyperplasia

No

Common

No

Eosinophil infiltration

Prominent

Prominent

Few

Food Challenge

Vomiting in 1–3 hours; diarrhea in
2–10 hours

Rectal bleeding in
6–72 hours

Vomiting and/or
diarrhea in 40–72 hours

Treatment

Protein elimination, ≥80% respond
to casein hydrolyzate and
symptoms clear in 3–10 days;
rechallenge in
1.5–2 years

Protein elimination,
symptoms clear in 3 days
with casein hydrolyzate;
resume/continue
breastfeeding on maternal
antigen-restricted diet

Protein elimination,
symptoms clear in
1–3 weeks; rechallenge
and biopsy in 1–2 years

Natural history

Cow’s milk: 60% resolved by 2 years
Soy: 25% resolved by 2 years

Resolved by 9–12 months

Most cases resolve in
2–3 years

Reintroduction of the food

Food challenge under physician
supervision with secure intravenous
access

At home, gradually
advancing from 1 oz to full
feedings over 2 weeks

Home, gradually
advancing

Reprinted with permission from Food Allergy, 4th edition; chapter 16. Eds. Metcalfe DD, Sampson HA, and Simon RA. Blackwell Publishing, 2008.

predispose to FPIES.4 Currently, the diagnosis of
FPIES is based on clinical criteria; endoscopy and
biopsy are not routinely performed. However, previous endoscopic evaluations and biopsies in infants
with FPIES identified diffuse colitis with variable
degrees of ileal involvement.1 Intestinal inflammation in FPIES may involve activation of peripheral
blood mononuclear cells (PBMCs), increased TNFα, and decreased expression of TGF-β receptors in
the intestinal mucosa1 (Table 11.2).
Systemic humoral antibody responses are usually
not detected in FPIES. The potential role of IgE
antibody produced locally in the intestinal mucosa
in facilitating the antigen uptake and local intestinal inflammation requires further study, but systemic IgE is usually not detected in FPIES. A decrease
in serum IgG antibody and an increase in serum
food-specific IgA levels has been noted; lower levels
of serum milk-specific IgG4 (p < 0.05) and a trend
for higher serum IgA antibody levels were found in
children with milk FPIES compared to the control
group.5

Clinical features
FPIES manifests as profuse emesis and diarrhea in
young infants and is most commonly caused by
milk and soy; over 50% react to both foods (Clinical Vignette 1). However, in a recent birth cohort in
Israel none of the 44 infants with cow’s milk FPIES
showed sensitivity to soy.2 Symptoms usually begin

Table 11.2  Pathologic findings in FPIES

Endoscopy
Friable mucosa
Minute spontaneous hemorrhage

Biopsy
Crypt abscesses
Villous atrophy
Tissue edema
Increased lymphocytes
Increased eosinophils and mast cells

Immunohistochemical
IgM- and IgA-containing plasma cells

In vitro studies
Increased activation of peripheral blood mononuclear cells
Increased TNF-α
Decreased expression of TGF-β receptors
Reprinted with permission from Food Allergy, 4th edition; chapter 16.
Eds. Metcalfe DD, Sampson HA, and Simon RA. Blackwell Publishing,
2008.

in early infancy (1–3 months, up to 1 year of age),
typically within 1–4 weeks following the introduction of milk or soy protein into the diet. Later onset
usually results from delayed introduction of milk,
soy, or solid foods in breastfed infants. FPIES to
milk and soy in infants that are exclusively breastfed is extremely rare, suggesting an important protective role of breastfeeding.6,7,8 FPIES to solid foods
such as grains, meats, fish, egg and vegetables have
145

Food Allergy

CLINICAL VIGNETTE 1

CLINICAL VIGNETTE 2

MILK FPIES

RICE FPIES

A 10-month-old boy who was born full term without
complications presented for evaluation. He was breastfed
from birth on an unrestricted maternal diet, although he
had received cows’ milk formula in the neonatal nursery as
supplementation as well as cows’ milk formula for a couple
of days at 2 months of life. Solids were introduced and
tolerated starting at 5 months and included cereals,
vegetables and fruits. At 8 months of age, yogurt was
introduced. Approximately 2 hours after eating two
spoonfuls of yogurt, he developed irritability and
repetitive, non-bloody, non-bilious vomiting. In addition,
he developed diarrhea later in the day. He did not have
associated fever. He was taken to the emergency
department, where he was found to be hypotensive and
listless. Examination revealed marked pallor. An
intravenous line was placed and normal saline given.
Given the extreme symptoms, a ‘rule out sepsis’ work-up
was conducted and intravenous antibiotics were started.
Serum chemistry revealed dehydration. Complete blood
count revealed leukocytosis with a left shift. His stools
were guaiac positive.

A 7-month-old girl presented for allergy evaluation. She
was initially breastfed with no maternal dietary restriction.
When she was supplemented with cows’ milk-based
formula she developed emesis and formula was
discontinued. She remained well on exclusive
breastfeeding and at 5 months solids were started. Rice
cereal was tolerated for about 2 weeks without any
problems. Thereafter, she developed multiple episodes of
forceful emesis within 2 hours of ingesting rice cereal.
During the first episode, emesis lasted for about 1.5 hours
and she became pale and lethargic. Ten days later, she was
again fed rice cereal and 2 hours later developed forceful,
non-bloody and non-bilious emesis; she passed a loose
stool with blood. She became lethargic, pale and
diaphoretic, but had no wheezing or skin rash. She was
rushed to the pediatrician’s office where she was treated
with epinephrine, dexamethasone and oxygen, and was
then sent to the emergency department, where she
improved with vigorous intravenous hydration. Rice
allergy was suspected, but allergy skin prick test and
serum rice-specific IgE were negative. The diagnosis of rice
FPIES was made. Fruits and vegetables were gradually
introduced to her diet at home and were tolerated well.
Wheat and cows’ milk were introduced to her diet at 1
year of age without any problems. She had no reactions to
any other foods. She continued to avoid rice.

Within 2 hours of IV fluids the patient’s condition improved
and his behavior returned to baseline. He was admitted to
the hospital for observation and IV antibiotics. He was
discharged when cultures were negative for 48 hours.
Two weeks after his admission, he ate a piece of cheese.
Again, he developed excessive vomiting and diarrhea
within 2–3 hours. He was brought to the emergency
department, where he required intravenous fluid
resuscitation, and within a few hours his baseline behavior
returned. His mother was certain that the symptoms were
the result of the cheese that he had eaten. Upon discharge
from the ER, recommendations included the continuation
of breastfeeding, milk avoidance, and evaluation by an
allergist.
Allergy evaluation revealed no concomitant atopic disease
such as atopic dermatitis or asthma. Family history was
significant for paternal allergic rhinitis and penicillin
allergy. Physical examination was unremarkable. Skin prick
testing was negative to milk with a negative saline control
and a positive histamine control. The diagnosis of milk
protein-induced enterocolitis syndrome was made based
on the clinical history. Recommendations included strict
milk avoidance and follow-up evaluation in approximately
1 year.

been reported usually with onset at 4–7 months of
age; onset of symptoms at older ages may occur
with some foods, such as fish or molluscs.9
In the most severe cases, symptoms may start
within the first days of life with bloody diarrhea,
lethargy, abdominal distension, weight loss, dehydration, metabolic acidosis, anemia, elevated white
146

blood count with left shift and eosinophilia, and
hypoalbuminemia. Among those with a recorded
complete blood count, 65% had thrombocytosis
>500 × 109/L.10 Intramural gas may be seen on
abdominal radiographs, prompting a diagnosis of
necrotizing enterocolitis, sepsis evaluation and
treatment with antibiotics. Overall, 75% of infants
with FPIES appear acutely ill; about 15% are hypotensive and require hospitalization.1
Transient methemoglobinemia was reported in
about one third of young infants with severe
reactions and acidemia; some required treatment
with methylene blue and bicarbonate. Methemoglobinemia may be caused by an elevation of
nitrites resulting from severe intestinal inflammation and reduced catalase activity. In 24% of acute
FPIES episodes, young infants manifested with
hypothermia <36°C.
Symptomatic infants improve within 3–10 days
with intravenous fluids or with casein hydrolyzatebased formula. Food reintroduction induces acute
symptoms; usually, repetitive emesis starts within
1–3 hours following ingestion, and diarrhea
starts within 2–10 hours (mean onset 5 hours),

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

11

Table 11.3  Clinical characteristics of cows’ milk and soy FPIES

Chronic manifestations during continued
ingestion of the food

Acute manifestations upon ingestion following
a period of food avoidance

Onset: days to 12 months

Onset: days to 12 months

Intermittent, chronic emesis

Repetitive emesis, onset 1–3 hours following ingestion

Chronic watery diarrhea with blood and mucus

Diarrhea, onset about 5 hours following ingestion

Lethargy

Lethargy, dusky appearance

Dehydration

Dehydration

Hypotensive shock (15%)

Hypotension in 15%

Acidemia

Acidemia

Methemoglobinemia/clinical cyanosis

Methemoglobinemia

Abdominal distension, hypoactive bowel sounds, ileus*

Abdominal distension, hypoactive bowel sounds, ileus*

Anemia

Frank or occult fecal blood

Elevated white blood count with eosinophilia

Elevated PMN count

Hypoalbuminemia

Thrombocytosis >500 × 109/L

Failure to thrive

Sheets of leukocytes and eosinophils in stool

Carbohydrate malabsorption (stool positive for reducing
substances)

Hypothermia <36°C in 24% of infants
Gastric juice leukocytosis (>10 cells/hpf)

*Ileus has been reported in extreme cases, typically newborns and young infants <3 months of age.
Reprinted with permission from Food Allergy, 4th edition; chapter 16. Eds. Metcalfe DD, Sampson HA, and Simon RA. Blackwell Publishing, 2008.

with blood, mucus, leukocytes, eosinophils and
increased carbohydrate content in the stool.11
However, not all patients develop diarrhea. Peripheral blood neutrophil counts are elevated in positive challenges, peaking at 6 hours. The typical
features of chronic and acute cows’ milk and soy
FPIES are presented in Table 11.3.
FPIES may be caused by solid foods such as rice,
oats, barley, chicken, turkey, molluscs, fish, egg
white, green pea and peanut1 (Clinical Vignette 2).
Rice is the single most common solid food inducing FPIES.12 Among infants with solid food FPIES,
65% were previously diagnosed with milk and/or
soy FPIES and fed with casein hydrolyzate- or
amino acid-based formula; 35% were breastfed.6
Mean age at onset of solid food FPIES tends to be
higher than the mean age of onset of milk and soy
FPIES.12 In our experience, solid food FPIES usually
starts at 4–7 months. Infants often present with
multiple reactions and extensive evaluations for
alternative etiologies (infectious, toxic or metabolic) before the diagnosis of FPIES is considered.
Delayed diagnosis may be due to the low index of
suspicion, since grains such as rice and oats, and
vegetables are believed to have low allergenic

potential and are not suspected as culprits in severe
allergic reactions. In addition, a lack of definitive
diagnostic tests and the unusual nature of symptoms may contribute to the delay in diagnosis. In
one study, infants with rice FPIES had severe symptoms and were more likely to receive fluid resuscitation upon presentation than those with milk or soy
FPIES (42% versus 15%, p = 0.02).12 In adults,
shellfish (including crustacean and molluscs) and
fish hypersensitivity may provoke a similar syndrome, with severe nausea, abdominal cramps, protracted vomiting and diarrhea.9

Diagnosis
Diagnosis is based on the history, clinical features,
exclusion of other etiologies, and food challenge
(Table 11.4). The majority (>90%) of patients have
negative skin prick tests and undetectable foodspecific IgE. Based on the presumed pathophysiology involving T cells, atopy patch test (APT) was
evaluated in 19 infants aged 5–30 months with
FPIES confirmed by an oral food challenge (OFC).13
APT predicted the outcome of an OFC in 28/33
instances; all positive OFCs had a positive APT, but
147

Food Allergy
Table 11.4  Oral food challenge in FPIES
Challenge protocol
•  High-risk procedure, requires physician supervision and
immediate availability of fluid resuscitation, secure
intravenous access
•  Baseline peripheral neutrophil count
•  Gradual (over 1 hour) administration of food protein
0.06–0.6 g/kg body weight, generally not to exceed 3–6 g
of protein or 10–20 g of total food for an initial feeding
•  If no reaction in 2–3 hours, administer a regular ageappropriate serving of the food followed by several hours
of observation
•  Majority (>50%) of positive challenges require treatment
with intravenous fluids and steroids
Criteria for a positive challenge
•  Symptoms
  Emesis (typically in 1–3 hours)
  Diarrhea (typically in 2–10 hours)
•  Laboratory findings
  Increase in peripheral neutrophil count > 3500 cells/mm3
peaking at 6 hours
  Fecal leukocytes
  Fecal eosinophils
  Gastric juice leukocytes >10 cells/hpf
Interpretation of the challenge outcome
•  Positive challenge: three of five criteria positive
•  Equivocal: two of five criteria positive












Reprinted with permission from Food Allergy, 4th edition; chapter 16.
Eds. Metcalfe DD, Sampson HA, and Simon RA. Blackwell Publishing,
2008.

five patients with positive APT did not react to an
OFC. Similar results have not been confirmed by
other investigators; therefore, the role of APT in the
diagnosis of FPIES requires further evaluation.
Although OFC is the gold standard for diagnosing
FPIES, most infants do not need to undergo
confirmatory challenges for the initial diagnosis,
especially if they have a classic history of severe
reactions and become asymptomatic following
elimination of the suspected food. However,
physician-supervised OFCs are necessary to determine whether FPIES has resolved, and whether the
food may be reintroduced into the diet.
Hypoalbuminemia and weight gain <10 g/day
were identified as independent predictors of milkFPIES in young infants with chronic symptoms.14
Stool examination in infants with chronic diarrhea
is non-specific and shows occult blood, intact polymorphonuclear neutrophils, eosinophils, Charcot–
Leyden crystals and reducing substances.
Prior to establishment of the diagnostic criteria,
endoscopy in symptomatic infants with cows’ milkand or soy FPIES showed rectal ulceration and
148

bleeding, with friable mucosa. In infants with
chronic diarrhea, rectal bleeding and/or failure to
thrive, radiographs showed air–fluid levels, nonspecific narrowing and thumb-printing of the rectum
and sigmoid, and thickening of the plicae circulares
in the duodenum and jejunum with excess luminal
fluid. In the cases of ileus, in which laparotomy was
performed, distension of small bowel loops and
thickening of the wall of jejunum distal to Treitz’s
ligament with diffuse subserosal bleeding was
reported. Follow-up studies performed on a restricted
diet in asymptomatic patients documented resolution of radiological abnormalities.1
OFCs can be used to establish a diagnosis of
FPIES or to evaluate the possibility that FPIES has
resolved. According to one conservative approach,
follow-up challenges are usually recommended
every 18–24 months in patients without recent
reactions.3 Korean investigators recommended a
more accelerated course, as they reported that
among 27 infants with milk FPIES, 64% tolerated
milk at 10 months and 92% tolerated soy at 10
months.15 They suggested that in milk FPIES the
first milk challenge should be done after age 12
months, whereas the first soy challenge could be
done between 6 and 8 months.

Oral food challenge
Guidelines for the preparation and interpretation
of the OFC for FPIES are presented in Table 11.4.
During an OFC, the total dose of 0.06–0.6 g/kg
food protein is administered in three equal portions over 45 minutes.16 Generally, the amount
served initially does not exceed 3–6 g of food
protein or 10–20 g of total food weight (usually
<100 mL of liquid food such as cows’ milk or infant
formula). The patient is observed for approximately 2–3 hours and, if asymptomatic, a second
feeding, typically an age-appropriate regular
serving, may be given followed by observation for
several hours.3 OFC in FPIES should be performed
under physician supervision with secure intravenous access for fluid resuscitation.16 Rapid intravenous hydration (20 mL/kg boluses) is the first-line
therapy. Intravenous corticosteroids are often used
for severe reactions, based on the presumed T-cellmediated intestinal inflammation.3 Epinephrine
should be available for potential severe cardiovascular reactions with hypotension and shock.
However, our unpublished experience is that
prompt administration of epinephrine does not

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

improve the symptoms of emesis and lethargy,
which do, however, resolve promptly with vigorous
intravenous fluid administration.
Gastric juice analysis was proposed as an additional confirmatory test in the equivocal oral
challenges.15 Gastric juice leukocytes >10 cells/high
power field (hpf) were observed in 15 of 16 positive
milk challenges after 3 hours, including two infants
without emesis or lethargy, whereas none of the
eight age-matched control infants had gastric juice
leukocytes >10/hpf. This observation needs to be
validated in larger groups of subjects.

Management
Management relies on avoidance of the offending
food. Extensively hydrolyzed casein formula is recommended for infants that cannot be breastfed
because concomitant milk and soy FPIES occur in
over 60% of cases. The majority of patients with milk
and or soy FPIES experience resolution of symptoms
within 3–10 days of starting extensively hydrolyzed
casein formula. Rarely, patients need amino acidbased formula or temporary intravenous fluids.
Because about one third of infants with cows’
milk or soy FPIES develop a reaction to solid food,
the introduction of yellow fruits and vegetables,
instead of cereals, at 6 months has been suggested.3,6
Infants with solid food FPIES are likely to react to
other foods: 80% are reactive to more than one
food protein, 65% react to milk and/or soy, and
those with a history of reactions to one grain have
at least a 50% chance of reacting to other grains.
Empirically, infants with solid food FPIES may
benefit from avoidance of grains, legumes and
poultry in the first year of life.3 In one approach the
introduction of milk and soy in infants without a
prior history of reactivity to these foods may be
attempted at an age older than 1 year, preferably
under physician supervision. Tolerance to one food
from each ‘high-risk category’, such as soy for
legumes, chicken for poultry, or oat for grains,
might be considered as an indication of increased
likelihood of tolerance to the remaining foods from
the same category.3
Milk FPIES resolves in 60%–90% and soy FPIES
resolves in 25% of patients by age 3 years (Clinical
Vignette 3).2,6,16 Resolution of solid food FPIES by
age 3 years occurred in 67% for vegetables, 66% for
oat and 40% for rice. FPIES rarely develops to foods
upon initial feeding beyond 1 year of age, although
onset of FPIES to fish and shellfish has been

11

CLINICAL VIGNETTE 3

NATURAL HISTORY OF FPIES
After 1 year of milk avoidance, our patient from Vignette 1
returned for follow-up evaluation. He had had no adverse
reactions to foods since his last visit; however, he had had
accidental ingestions of foods that contained milk (i.e.
cookie, bread prepared with butter). An oral food
challenge to milk was recommended and conducted
approximately 6 months after the follow-up visit (18
months from his original evaluation).
On the day of the food challenge, an intravenous line was
placed prior to feeding milk. The patient tolerated two
separate feedings of milk (total of 0.6 g of protein per kg).
He was observed for 3 hours following the second feeding.
On discharge from the challenge, the family was advised
to add milk into the diet.

reported in older children and adults. For example,
wheat allergy has not been reported in infants with
oat- or rice-induced FPIES, but the introduction of
wheat was significantly delayed, presumably avoiding the ‘window of physiologic susceptibility’ for
FPIES development.3,6 Patients presenting initially
or developing food-specific IgE antibodies after the
diagnosis of FPIES have a more protracted course.6,16
It may be prudent to include skin prick testing and/
or measurement of serum food-specific IgE level in
the initial as well as follow-up evaluations, to identify patients at risk for persistent FPIES.

Food protein-induced proctocolitis
Food protein-induced proctocolitis is a benign transient condition which typically begins in the first
few months of life with blood-streaked stools in
well-appearing infants; it is considered one of the
major causes of colitis under age 1 year9 (Table 11.5).
Table 11.5  Key features of food protein-induced
proctocolitis
Usually presents by 6 months of life
Blood streaked, loose stools ± diarrhea in otherwise
well-appearing infants
Usually occurs in breastfed (60%) or cows’/soy milk
formula-fed infants (40%)
Diagnosis is based on clinical history
Food prick skin test and serum food-IgE negative
Treatment is based on food protein elimination
Resolution of symptoms in 48–72 hours following food
protein elimination
Tolerance to allergen usually occurs by 1–3 years of life

149

Food Allergy

Food protein-induced proctocolitis was originally
described by Lake et al. in 1982 in six exclusively
breastfed infants with rectal bleeding that appeared
during the first month of life.17

Epidemiology
In contrast to other forms of gastrointestinal food
hypersensitivity, proctocolitis is prevalent in breastfed infants, making up as many as 60% of cases in
published reports.17 The exact prevalence of allergic
proctocolitis is unknown; the estimated prevalence
ranges from 18% to 64% of infants with rectal bleeding.18,19 Eczema is present in about 22% of the
breastfed infants. A positive family history of atopy
is present in up to 25% of infants with proctocolitis, which is comparable to the general population.20

Pathogenesis
Food protein-induced proctocolitis most commonly affects the rectosigmoid. Endoscopy reveals
focal erythema with lymphoid nodular hyperplasia.
Biopsy reveals prominent eosinophilic infiltrates in
the rectal mucosa; the number of eosinophils varies
from 6 to >20 per 40 hpf; eosinophils are frequently
degranulated and localized next to the lymphoid
nodules. The pathologic findings are similar to
those that can be identified in other forms of eosinophilic gastrointestinal disorders; lack of additional symptoms and a mild course support the
diagnosis of allergic proctocolitis in an infant with
isolated rectal bleeding. There is no correlation
between the degree of peripheral blood eosinophilia and the tissue eosinophilic infiltrate
within the rectosigmoid. Eosinophil mediators
induce mast cell degranulation, dysfunction of
vagal muscarinic M2 receptors, smooth muscle constriction, and stimulation of chloride secretion
from colonic epithelium. Degranulation of the
eosinophils near nerves may contribute to gastric
dysmotility. Additionally, experimental eosinophil
accumulation in the gastrointestinal tract is associated with the development of weight loss.21
Table 11.6 summarizes the most important pathologic features of food protein-induced proctocolitis.
Lake20 postulated that food protein-induced
proctocolitis represents a milder form of FPIES
because in both conditions the strongest inflammatory response occurs usually in the rectum. Proctocolitis in formula-fed infants would represent the
mildest phenotype, whereas in breastfed infants it
150

Table 11.6  Pathologic findings in food protein-induced
proctocolitis

Endoscopy
Rectosigmoid affected most commonly
Focal erythema and inflammation
Lymphoid nodular hyperplasia
Rectal ulcerations

Mucosal biopsy
Normal architecture preserved
Eosinophilic infiltration (6 to >20 per 40× high power field)
Features of eosinophil degranulation
Occasional eosinophilic crypt abscesses

would represent the attenuated FPIES due to the
protective effects of the breast milk, such as the
presence of IgA antibodies, TGF-β and partially
processed food proteins. This concept is supported
by the lack of published reports of classic FPIES in
breastfed infants. IgA or other immunologically
active components of breast milk may bind with
the food allergens and release them in the rectum
following cleavage by microbial IgA proteases or via
other mechanisms.20

Clinical features
Food protein-induced proctocolitis in formula-fed
infants is typically caused by cows’ milk and soy
proteins; in breastfed infants it is usually caused by
cows’ milk, soy, egg and corn proteins (Clinical
Vignette 4). Infants appear healthy, but parents
typically note a gradual onset of bloody stools,
which increase in frequency unless the triggering
food is eliminated.20 Children with proctocolitis
do not have poor weight gain but may develop
mild anemia17 or hypoalbuminemia. Some have
peripheral blood eosinophilia, elevated serum IgE
antibody levels and a positive family history of
atopy.22–25 Infants usually present in the first 4
months of life, usually at 1–4 weeks of age, with
intermittent blood-streaked normal to moderately
loose stools (Table 11.5). Breastfed infants are often
older at the time of initial presentation and have
less severe histologic findings. The onset may be
acute (<12 hours following the first feeding of the
offending food) but is more often insidious, with a
prolonged latent interval between the introduction
of the food protein and the onset of symptoms. The
affected infants typically appear well; however,
increased gas (up to 30% of patients), intermittent

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

CLINICAL VIGNETTE 4

FOOD PROTEIN-INDUCED PROCTOCOLITIS
An 11-month-old breastfed boy presented for evaluation
of food allergy. He had been breastfed since birth without
any maternal dietary restrictions, and supplemented with
cows’ milk-based formula, on average four to five times
a week. At 8 weeks of age gross blood was noted in the
stool and he appeared uncomfortable. There was no rectal
fissure and no signs of an infection. Allergic proctocolitis
was suspected and cows’ milk formula was discontinued
and milk products were eliminated from his mother’s diet,
with some improvement but without complete resolution
of the bloody stools. The pediatric gastroenterologist
suspected food protein-induced proctocolitis and
recommended stopping soy in the maternal diet.
Apparently, the mother had started ingesting significant
amounts of soy milk to substitute for cows’ milk, and when
she discontinued soy milk there was a significant
improvement in the amount of visible blood in the stools.
His stools became entirely negative for gross blood within
4 days of elimination of delicatessen meats in the mother’s
diet that were suspected for probably being contaminated
with traces of cheese during the process of slicing.
Subsequent stool checks were negative for occult blood.
He continued to be breastfed with maternal dietary
restrictions for cows’ milk and soy protein. The patient
tolerated gradual introduction of solid foods (rice cereal,
yellow fruits and vegetables) starting at the age of 6
months without any problems. His personal history of
atopy was negative for atopic dermatitis, wheezing or
chronic rhinitis.
On presentation to the allergy office the patient was a
healthy infant, weighing 11.8 kg (90th percentile ) and
height 80.6 cm (>95th percentile). Allergy evaluation with
skin prick tests to commercial milk and soy extract and
measurement of serum milk and soy IgE (UniCap, Phadia)
revealed negative results.
Based on his clinical manifestations the child was
diagnosed with cows’- and soy-milk-induced allergic
proctocolitis. His mother was advised to gradually
introduce soy and cows’ milk products into her diet, prior
to directly feeding these two foods to her son after his first
birthday. He tolerated soy and milk in his diet without any
adverse reactions, and breastfeeding was discontinued
when he was 14 months old.

emesis (up to 27%), pain on defecation (22%) or
abdominal pain (up to 20%) may be present. No
anatomic abnormalities are found and stool cultures are negative for pathogens. Smears of the fecal
mucus usually reveal increased polymorphonuclear
neutrophils.
Breastfed infants react to the cows’ milk proteins
consumed by the mother. Elimination of cows’
milk from the mother’s diet usually results in

11

gradual resolution of symptoms in the infant and
permits the continuation of breastfeeding.17,25,26
Rarely, a casein hydrolyzate formula, or in rare
instances an amino acid-based formula, may be
necessary for resolution of bleeding, typically
within 48–72 hours.9
Sometimes breastfed infants continue to have
bleeding despite maternal avoidance of food(s); six
of 21 of these infants developed iron deficiency
anemia despite iron supplementation, but they
gained weight and had normal development and
by their first birthday were tolerating a regular
diet.20 The persistence of rectal bleeding despite
maternal dietary restrictions may be explained by
inability to remove all sources of allergen from the
diet, or by an allergen that has not been identified.
Alternatively, the baby might react to the human
breast milk protein.

Diagnosis
Diagnosis relies on a history of rectal bleeding and
response to an elimination diet which typically
leads to a clinical resolution of gross bleeding
within 72–96 hours.20 Tests for IgE-mediated food
hypersensitivity are negative or inconsistent, and
usually not useful for the diagnosis of food proteininduced proctocolitis. Excluding causes of rectal
bleeding, such as infection, necrotizing enterocolitis, intussusception or anal fissure, is important.

Management
Treatment is based on dietary restriction. In breastfed infants, Lake20 proposed discontinuation of
breast milk and feeding with a casein hydrolyzate
formula until resolution of bleeding, usually within
72 hours. Soy formula may cause bleeding in a large
subset of infants reacting to cows’ milk because up
to 40% of infants react to both foods.20 Most infants
respond well to casein hydrolyzate formulas and
only few require amino acid-based formulas.
Breastfeeding mothers must strictly avoid the
offending food protein in their diet. Rechallenge
within the first 6 months usually induces recurrence
of bleeding within 72 hours. In contrast to FPIES,
no peripheral blood leukocytosis is seen following
the challenge.9,17 If food skin prick tests and serum
food-specific IgE antibody levels are negative,
gradual food introduction typically takes place at
home, increasing from 1 oz/day to full feedings
over 2 weeks.27
151

Food Allergy

Infants with proctocolitis usually become tolerant to the offending food by 1–3 years of age and
the majority achieve clinical tolerance by 1 year. Up
to 20% of breastfed infants have spontaneous resolution of bleeding without changes in the maternal
diet.21 The long-term prognosis is excellent, and
there are no reports of inflammatory bowel disease
in infants with food protein-induced proctocolitis
followed for more than 10 years.20,28

Food protein-induced enteropathy
Food protein-induced enteropathy is a syndrome of
small bowel injury with resulting malabsorption,
similar to celiac disease albeit less severe.9 The first
report of malabsorption syndrome with diarrhea,
emesis and impaired growth induced by cows’ milk
formula in infants was published in 1905. Subsequent reports, including large series of cows’ milk
protein-sensitive Finnish infants, defined the clinical features of this disorder29–35 (Table 11.7).

Epidemiology
Reports of food protein-induced enteropathy
peaked in the 1960s in Finland, with virtual disappearance in the past 20 years.36 The highest incidence of classic severe enteropathy was observed in
infants fed with non-humanized milk-based formulas, and the lowest incidence was observed in
breastfed infants. Infants with enteropathy typically
do not have a predisposing family history of food
allergy. More recently, intestinal enteropathy was
reported in older children with delayed-type allergic reactions to milk, as well as in children with
multiple food allergies.37–39

Pathogenesis
Activated T lymphocytes expressing HLA-DR appear
to play a central role in the pathophysiology of food
protein-induced enteropathy; following milk elimination, these cells diminish.40 Histological changes
are consistent with enteropathy and allergic inflammation. The histological features of soybean- or
cereal-induced enteropathy are similar to those
noted for milk. Immunohistochemical studies of
the mucosal biopsies in untreated and challengepositive infants demonstrate an increase in mucosal
IgA, IgG and IgM, with inconsistent increase in
IgE. An elimination diet following a positive challenge results in decreased densities of IgA- and IgMcontaining cells.41 Similar changes in IgA and IgM
cells were observed in soy-induced enteropathy following an oral challenge with soy and reinstitution
of an elimination diet. Table 11.8 summarizes the
most important pathologic and immunologic
features of food protein-induced enteropathy.
Table 11.8  Pathologic findings in protein-induced
enteropathy

Mucosa
Thin mucosa
Crypt hypertrophy and thinning
Villous blunting and atrophy (patchy, subtotal)
Reduced crypt : villus ratio
Shortened microvilli
Thickened basement membrane (unevenly)
Prominent intraepithelial lymphocytes
Increased mucosal lipid content
Eosinophilic infiltration (inconsistent)

Lamina propria
Increased lymphocytes, plasma cells, eosinophils
Tissue and blood vessel endothelium edema
Increased histamine content
Degranulation of mast cells and eosinophils

Immunohistochemical studies
Table 11.7  Key features of protein-induced
enteropathy
Onset dependent upon introduction of food antigen to diet:
usually by 9 months for cows’ milk
Vomiting and diarrhea mimic gastroenteritis but are
protracted; may lead to failure to thrive
Usually occurs in cows’/soy milk formula-fed infants
Diagnosis is based on clinical history
Food prick skin tests and serum food-IgE are usually negative
Anemia and hypoalbuminemia are common
Treatment is based on protein elimination
Resolution of symptoms in 1–3 weeks
Tolerance to food allergen usually occurs by 2–3 years of life
152

Increased mucosal IgA, IgG and IgM
Increased mucosal IgE (inconsistent)
Increased α/β suppressor/cytotoxic CD8+ T cells
Increased density of γ/δ T cells
Activated T cells (HLA-DR+)
Increased gut homing receptor α4/β7 expression on T cells

In vitro studies
Increased IFN-γ and IL-4
Decreased IL-10
Decreased TGF-β
Reprinted with permission from Food Allergy, 4th edition; chapter 16.
Eds. Metcalfe DD, Sampson HA, and Simon RA. Blackwell Publishing,
2008.

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

CLINICAL VIGNETTE 5

FOOD PROTEIN-INDUCED ENTEROPATHY
A 9-week-old girl presented with a 4-week history of
diarrhea, intermittent emesis and failure to thrive. She was
breastfed exclusively for 4 weeks and then switched to
cows’ milk-based formula. Physical examination revealed
mild eczema. Laboratory testing showed peripheral blood
eosinophilia, mild anemia and low serum total protein.
Stools were positive for occult blood and had increased fat
content, indicating malabsorption. Endoscopy and biopsy
showed subtotal villous atrophy in the proximal jejunum.
The child was switched to a hypoallergenic formula and
her symptoms gradually resolved in 3 weeks.

Clinical features
Food protein-induced enteropathy presents with
chronic diarrhea within weeks after the introduction of milk formula, usually in the first 1–2 months
of life, but may start as late as 9 months (Clinical
Vignette 5). Foods such as soy, wheat and egg have
also been confirmed as causes of enteropathy, frequently in children with coexistent milk proteininduced enteropathy. The affected infants have
vomiting and failure to thrive; some present with
abdominal distension, early satiety and malabsorption. The onset of symptoms is usually gradual;
however, it may also mimic acute gastroenteritis,
with transient emesis and anorexia complicated by
protracted diarrhea. It may be difficult to distinguish food protein-induced enteropathy from postenteritis-induced lactose intolerance, especially
since the two conditions may overlap. Acute small
bowel injury caused by viral enteritis has been postulated to predispose children to subsequent food
protein-induced enteropathy, or alternatively to
unmask underlying food protein hypersensitivity.
Diarrhea usually resolves within 1 week of cows’
milk protein elimination, although some infants
require prolonged intravenous nutrition.
Moderate anemia is present in 20–69% of infants
with cows’ milk protein-induced enteropathy. Iron
deficiency is more common than anemia, probably
owing to the malabsorption of iron or folate.
Bloody stools are absent, but occult blood can be
found in some patients. Malabsorption with hypoproteinemia and deficiency of vitamin K-dependent
factors has been reported in 35–50%. Moderate
steatorrhea, manifested by increased fecal fat excretion, can be found in over 80%. The absorption of
the sugar d-xylose test is abnormal in up to 80%.
Lactose can be found in the urine in 55% and in

11

the stool in 52% of cases, typically in the youngest
infants. Lactose absorption normalizes promptly
following the elimination of milk protein.
School-aged children with delayed gastrointestinal symptoms to milk challenge but without villous
atrophy or malabsorption have been reported.37
Twenty-seven children with suspected milk-related
symptoms, such as a history of milk allergy in infancy,
abdominal pains or diarrhea after consumption of
dairy products, were placed on strict elimination of
milk protein for 2 weeks, followed by a challenge
over 1 week. All children responded clinically to milk
elimination, but only 15 (mean age 10 years, range
6–14) had relapse of symptoms during 1-week challenge. Compared to control children (11 with celiac
disease, 12 without gastrointestinal disease), they
had a history of significantly greater food allergy at
<2 years of age, gastritis and esophagitis on biopsy,
as well as lymphonodular hyperplasia of the duodenal bulb. Increased γ/δ T lymphocytes were noted,
but of lesser magnitude than in celiac disease. These
older children may represent a subset of milder
enteropathy or they may have a different disease
caused by milk hypersensitivity.
Subsequent reports confirmed subtle enteropathy
in children with delayed gastrointestinal symptoms
following food ingestion.38,42 One study evaluated
seven children with untreated food allergy (mean
age 7.3 years, range 2–13), seven with treated food
allergy (mean age 8.1 years, range 1–14), and five
normal controls (mean age 11.4, range 4–16). Diagnosis of food allergy was based on resolution of
gastrointestinal symptoms during 2 weeks of an
elimination diet and reappearance of symptoms in
an open food challenge within a median 4.5 days,
range 1–7 days. Children reacted to milk, cereal
grains or both. Five of eight children tested had specific serum food-specific IgE >0.7 kIU/L or a positive
skin prick test. Biopsies demonstrated lymphonodular hyperplasia in the small intestine in 90%. The
untreated children with food allergy exhibited a
higher crypt proliferation rate and HLA-DR crypt
staining than the controls. In most duodenal biopsies obtained from 45 children with both immediate
and delayed history of multiple food allergies, there
was focal lymphocytic or eosinophilic infiltration,
villous blunting and reduced crypt : villus ratio.39

Diagnosis
Food protein-induced enteropathy is diagnosed
by finding villous injury, crypt hyperplasia and
153

Food Allergy

inflammation on small bowel biopsy in a symptomatic patient who is ingesting the offending food
allergen. Avoidance of the allergen usually leads to
resolution of clinical symptoms within 1–3 weeks.
Villous atrophy usually improves within 4 weeks,
but complete resolution may take up to 1.5 years.
Infants with severe initial manifestations may
require prolonged bowel rest and parenteral nutrition for days or weeks. Diagnostic challenges and
measurement of specific serologies for celiac disease
may be necessary to exclude celiac disease, or to
identify multiple food allergens. In clear-cut cases
OFCs are not absolutely required for diagnosis.
However, challenges should be performed periodically to assess the development of oral tolerance.
Increased levels of milk serum IgA in 74% and
milk serum IgG precipitins were found in 65% of
infants. Milk IgA levels decreased following dietary
elimination of cows’ milk.32 The diagnostic utility
of these tests is unknown, particularly in view of
the high prevalence of positive results in many
other gastrointestinal inflammatory disorders in
childhood. Food-specific serum IgE antibodies are
usually undetectable and skin prick tests are negative. Patch skin tests were investigated as a screen
for gastrointestinal food hypersensitivity (milk,
wheat), but biopsies were not obtained and the
association of positive patch tests with gastrointestinal changes remains to be determined.43
Serum concentrations of granzymes A (GrA) and
B (GrB), soluble Fas and CD30 were measured in
children with milk-sensitive enteropathy confirmed
by endoscopy and biopsy.44 These markers reflect
activation of cytotoxic lymphocytes that have been
shown to be upregulated in the local intestinal
mucosa in food-sensitive enteropathy. Serum concentrations of GrA and GrB were significantly higher
in the untreated children with food allergy and in
the children with celiac disease than in the control
subjects. Measurable serum GrB was present in only
20% of the control subjects but in 100% of patients
with milk-sensitive enteropathy. Patients with
untreated milk-sensitive enteropathy and celiac
disease exhibited similarly increased CD30, whereas
treated patients exhibited concentrations that were
not different from those in control subjects. All
groups showed similar levels of soluble Fas. The
numbers of duodenal CD3+ α/β- and γ/δ-TCRs
correlated with the serum granzyme and CD30
levels. These preliminary results are very encouraging for the identification of biomarkers, but must
be confirmed in a larger number of patients before
154

measurement of serum markers of intestinal cytotoxic lymphocyte activation may be routinely used
to diagnose and monitor response to elimination
diets.

Treatment/management
Food protein-induced enteropathy resolves clinically in the majority of children by age 1–2 years,
but the proximal jejunal mucosa may be persistently abnormal at that time.32 Mucosal healing continues during feeding with the implicated food once
clinical tolerance is achieved.45 The majority of children with less severe disease who were diagnosed at
an older age became tolerant by 3 years.46 About
10% of infants with challenge-confirmed cows’
milk-induced enteropathy were ultimately diagnosed with celiac disease that persisted beyond
infancy.32 In contrast, transient wheat enteropathy
with or without associated cows’ milk proteininduced enteropathy has been reported in a number
of studies, including transient wheat enteropathy
following enteritis.47–49 Strict criteria for the diagnosis of transient wheat-induced enteropathy were
established and include evidence of small bowel
villous injury, resolution with gluten avoidance, and
persistent normal small bowel mucosa for 2 or
more years after the reintroduction of gluten to the
diet.50 The course of food protein-induced enteropathy in older children has not been characterized.

Infantile colic
Infantile colic is a common condition of paroxysmal, prolonged, excessive and inconsolable crying
in an otherwise healthy infant. Colic lacks a formal
definition or a standard set of diagnostic criteria
(Table 11.9). The most commonly used criteria
stem from Wessel in 1954, who described infantile
colic as unexplained paroxysmal bouts of irritability, fussing or crying lasting > 3 hours a day for > 3
days a week for at least 1 week in duration, or, if
severe, more than 3 weeks.52 Excessive crying in
infancy causes much distress to the infant, the
family and the physician, and may have long-term
implications for how the family views the child and
the healthcare system. That being said, infantile
colic itself is a benign and self-limiting condition.

Epidemiology
Infantile colic usually begins within the first weeks
of life and resolves by 3 months of age in 60% of

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

Table 11.9  Diagnostic criteria for infantile colic

Table 11.10  Proposed causes of infantile colic

Wessel’s rule of threes

Dietary

Crying for: More than 3 hours per day
More than 3 days a week
For at least 3 weeks

Food hypersensitivity
Lactose intolerance
Carbohydrate malabsorption

Characteristics of crying episodes

Gastrointestinal

Paroxysmal
Inconsolable
Excessive
Typically occurs late afternoon or early evening
Infant is normal between episodes

Intestinal hypermotility
Feeding difficulties
Gut hormones
Imbalance of gut microflora
Gastroesophageal reflux
Excessive gas
Irritable bowel

Physical features
Clenched fists
Stiff arms
Flexed legs, or legs drawn up
Arched back
Facial grimacing
Flushing
Abdominal distension
Passing of gas

infants and by 4 months in 90%.53 The occurrence
rate varies widely between 3–40%, depending on
the population studied and the case definition
used.54 There seems to be no predilection for gender,
full-term versus preterm, birthweight, breastfed
versus formula-fed, or maternal level of education,
parity or ethnicity.52,55,56 Risk factors that have been
associated with colic include living in a Western
society, family stress and/or dysfunction, birth
order, family history, and lack of parental confidence, all of which are probable confounders that
increase the likelihood that parents will seek
medical attention.52,57

Psychosocial
Temperament
Environmental hypersensitivity
Family stress
Parent–child interaction

often occur during crying episodes. Based on existing studies, 10–15% of infantile colic cases may be
due to food allergies or intolerance.59,60 Food hypersensitivity, particularly to milk and/or soy, may play
a role in colic for a subgroup of infants (Clinical
Vignette 6). Studies that have explored the colic–
food hypersensitivity association are summarized
in Table 11.11.
It has been suggested that infantile colic may represent an early manifestation of cows’ milk allergy,61
and that infants with a personal or family history
of atopy should be given a trial off cows’ milk.62
Colic has not been associated with elevated serum

Pathogenesis

CLINICAL VIGNETTE 6

Medical conditions account for <5% of excessive
crying or irritability.58 Pediatricians also look for
simple yet often overlooked physical causes of
sudden-onset crying, such as hair tourniquets (a
hair wrapped around a digit), anal fissures or
corneal abrasions. The cause of infantile colic is
most likely multifactorial, represented by three
main categories: dietary, gastrointestinal or behavioral (Table 11.10).

COLIC AND FOOD ALLERGY

Colic–food hypersensitivity association
Not surprisingly, many studies have focused on diet
as a cause of infantile colic owing to behavioral
signs suggestive of gastrointestinal distress that

11

A full-term male infant developed inconsolable crying at
2 weeks of age. He was exclusively breastfed from birth
without any maternal dietary restrictions. During crying
episodes, he appeared very uncomfortable and his legs
were drawn up. He had frequent spit ups and frequent
foul-smelling stools without blood or mucus. He had signs
of cradle cap and developed an itchy rash on his cheeks
and abdomen at 6 weeks, which improved slightly with
topical corticosteroids. His birthweight was in the 75th
percentile and gradually decreased to the 50th percentile
by 2 months of age. Serum-specific IgE antibodies were
detected to cows’ milk 5 kIU/L and egg 1 kIU/L. Maternal
restriction of cows’ milk, soy and egg products resulted in
resolution of his colic and significant improvement of his
eczema within 1 week.
155

156
43 formula-fed

Double-blind
crossover

Cohort

RDBPCT

Lothe 198966

Iacono 199167

Lucassen
200062

Evans 198168

Double-blind
crossover

70 formula-fed

Double-blind
multiple crossover

Forsyth 198965

Breastfed

19 formula-fed

Double-blind
crossover

Campbell
198964

20 breastfed

27 formula-fed

17 formula-fed

60 formula-fed

No. of
subjects

Double-blind
crossover

Type of study

Lothe 198263

Formula-fed

Authors

Replaced cows’ milk
with soy milk in
maternal diet

Whey hydrolyzate
formula (WHF)

Soy formula

CHF; challenge with
whey vs placebo
capsule

Three formula
changes with
subjects receiving
alternatively CHF or
cows’ milk formula

Soy formula, if
needed lactoalbumin
hydrolyzate formula

Soy formula, if
needed casein
hydrolysate formula
(CHF)

Intervention

Table 11.11  Summary of studies investigating hypoallergenic diets in colic

No effect of soy milk; noted increased colic on days when mothers ate
chocolate or fruit

Decrease in crying by 63 min/d on WHF (p = 0.05)

50/70 (71.4%) improved on soy formula and relapsed w/in 24 h on 2
subsequent cows’ milk challenges. 8/50 showed signs of soy intolerance
within 3 weeks.

Less crying with formula change: 0.7 h/d in CHF group vs. 5.6 h/d in control
group (p < 0.001)
Increased crying with challenge: 3.2 h/d in whey group vs 1 h/d in placebo
group (p < 0.001)

Less crying and less colic on CHF with 1st formula change (p < 0.01)
Less colic on CHF with 2nd formula change (p < 0.05)
No difference on 3rd formula change

69% improved with formula change (11% with soy, 2% with lactoalbumin
hydrolyzate formula) vs 5% (n = 1) no change (p < 0.001); 26% (n = 6) had
spontaneous improvement

71% improved with formula change (18% with soy, 53% with CHF); 29% of
cases not related to formula

Results

Food Allergy

Double-blind
crossover

Cohort

Randomized
controlled

Jakobsson
198369

Estep 200070

Hill 200571

Cohort

Iacono 199167
70 formula-fed

60 formula-fed

90 breastfed

6 breastfed

66 breastfed

No. of
subjects

Soy formula

Soy formula, if
needed CHF

Low allergen
maternal diet (no
milk, soy, wheat, egg,
peanut, tree nut, fish)

Amino acid formula
(AAF) and maternal
elimination of cows’
milk, then
reintroduction of
breast milk

Maternal elimination
of cow’s milk,
challenge with whey
vs placebo capsules

Intervention

22/50 (44%) of group that responded to formula change showed cows’ milk
intolerance at a mean follow-up time of 18 mo vs one infant (5%) in the
non-responder group (p < 0.02)

Group that responded to formula change showed higher incidence of cows’
milk intolerance than normal population at 6 mo follow-up (18% vs. 1.6%)
and 12 mo follow-up (13% vs. 1%)

Absolute risk reduction on low allergen diet was 37% (p < 0.001); based on
reduction of infant distress by ≥ 25% mother’s assessment indicated no
difference
In previous study, same group found that the effect of a low allergen
maternal diet was more pronounced in infants <6 wks old (p < 0.001) vs
>6 wks old (p < 0.05)

All infants improved on AAF
All infants tolerated reintroduction of breast milk after maternal elimination
of cows’ milk

35/66 (53%) showed resolution of symptoms with elimination of cows’ milk
in maternal diet and 23/35 (35%) showed recurrence with reintroduction of
cows’ milk
9/16 (56%) infants showed increased symptoms on whey challenge

Results

RDBPCT, randomized double-blind placebo-controlled trial; CHF, casein hydrolyzate formula; WHF, whey hydrolyzate formula; AAF, amino acid formula.

Double-blind
crossover

Lothe 198263

Follow-up

Type of study

Authors

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

11

157

Food Allergy

total or food-specific IgE levels; however, young
infants have low baseline serum-specific IgE concentrations and poor skin reactivity on skin testing,
making diagnostic food allergy testing difficult at
an age when they exhibit colic.59 Some studies have
reported that infants with a history of colic who
responded to a change of formula have a higher
likelihood of cows’ milk intolerance later on (Table
11.11).63,67
Studies investigating the possible connection
between colic and atopy have been conflicting. In a
prospective cohort study of 320 children, cows’
milk allergy (p < 0.0005) and other allergies (p <
0.05), but not asthma or eczema, were reported to
be significantly increased in children at age 3.5
years who had a history of feeding or crying problems during infancy.72 A prospective 10-year study
on 96 children, half of whom had a history of
infantile colic, found an association between infantile colic and allergic disorders (allergic rhinitis–
conjunctivitis, asthmatic bronchitis, pollen allergy,
atopic eczema and food allergy) (p < 0.05), and
between infantile colic and a family history of GI
and atopic disease (p < 0.05).73 In contrast, the
Tucson Children’s Respiratory Study found no association between infantile colic and markers of
atopy, asthma, allergic rhinitis, wheezing or peak
flow variability at any age.56

Clinical features and diagnosis
Commonly observed patterns in colic include
the time of day when crying episodes occur and
associated physical behavior (Table 11.9). Crying
episodes most often occur in the late afternoon
or early evening.52,57,74 Hypertonia, exhibited as
clenched fists, stiff arms, flexed legs, arching of
the back and facial grimacing, along with signs of
flushing, abdominal distension, regurgitation and
passing of gas, is typical.51 The diagnosis of colic is
made predominantly by history, and often using a
version of Wessel’s criteria.

Treatment
As in studies on causal factors of infantile colic, a
wide diversity of case definitions, inclusion/
exclusion criteria and outcome measurements
make it difficult to compare the effectiveness of
different colic treatments. One systematic review
of infantile colic treatments concluded that four
interventions were significant: hypoallergenic diet
158

(number needed to treat (NNT) in order for one
case of colic to improve = 6), soy formula (NNT =
2), reduced stimulation (NNT = 2) and herbal tea
(NNT = 3).75 Proposed interventions that have been
studied are reviewed in Table 11.12.
Several studies concluded that hypoallergenic
diets may be beneficial in infantile colic. Some
studies have shown improvement of colic with the
introduction of soy formula; however, because
some colicky infants are sensitive to both cows’
milk and soy, a hydrolyzate formula may be a better
choice. No studies have compared soy formula
directly with hypoallergenic formula.

Management
An otherwise healthy infant <5 months old who
exhibits crying for more than 3 hours/day for
more than 3 days/week may be considered colicky.
Table 11.13 lists strategies for managing a colicky
infant. When evaluating an infant who presents
with excessive crying, basic needs such as feeding,
diaper changing and sleeping should be addressed,
and more serious medical conditions ruled out first.
The next most important management step is
parental support. Most techniques for soothing a
crying infant are anecdotal, but typically minimally
invasive and benign. Feeding techniques such as
frequent burping, an upright position while feeding
and special bottles that reduce air bubbles have
been suggested. Other methods focus on altering
stimulation with, for example, pacifiers, changes
in ambient temperature or scenery, swings, warm
baths, massages, crib vibrators, secure car seats
on a clothes dryer, and various sources of white
noise.
Hypoallergenic diets have shown some efficacy in
reducing colic symptoms for a subgroup of colicky
infants, although how to identify which infants fall
into this subgroup is unclear. Even though data on
whether colic may actually represent an early manifestation of allergy are few, it would be reasonable
to try diet management in infants with a personal
or family history of atopy. Diet management might
also be a good option if gastrointestinal symptoms
such as vomiting, cramping or diarrhea are present,
or if colic symptoms are associated predominantly
with feeds. If the infant is formula-fed, switching to
a hydrolyzed formula rather than a soy formula
may be more efficacious because of the frequent
intolerance to both cows’ milk and soy. If the infant
is breastfed and the mother would like to attempt

FPIES, Food Protein-Induced Enteropathy, Proctocolitis, and Infantile Colic 

11

Table 11.12  Interventions for infantile colic

Intervention

Current understanding of effectiveness

Dietary
Hydrolyzed formula

Beneficial for some (several studies)*

Soy formula

Significant crossover between cows’ milk and soy intolerance (several studies)*

Low-allergen maternal diet

Beneficial for some (several studies)*

Fiber-enriched formula

Lacks evidence (1 RCT)76

Oral lactase or lactase-treated feeds

Inconclusive (2 RCT show no benefit, 2 RCT show benefit)77,78,79,80

Pharmaceutical
Antireflux medication

Lacks evidence (2 RCT)81,82

Simethicone

Lacks evidence (3 RCT); no adverse effects83,84,85

Anticholinergic

Beneficial (4 RCT); case reports of serious side effects; contraindicated86,87,88,89

Cimetropium bromide

Beneficial (1 RCT); side effect increased sleepiness; needs additional safety studies90

Alternative therapies
Probiotics

Beneficial (2 RCT showed benefit, 1 RCT showed no benefit with different strains for a
shorter period); needs additional studies91,92,93

Sucrose/Glucose

Beneficial (3 RCT); effects short-lived94,95,96

Herbal tea/extract

Beneficial (3 RCT); needs standardization and safety studies97,98,99

Spinal manipulation

Inconclusive (1 RCT showed benefit, 1 RDBPCT showed no benefit); not recommended100,101

Behavioral
Decreased stimulation

Beneficial (1 RCT)102

Intensive parental training

Beneficial (2 RCT)103,104

Increased carrying of infants

Lacks evidence (1 RCT); still suggested for reduction of infant and parental stress105

RCT, randomized controlled trial.
*RDBPCT, randomized double-blind placebo-controlled trial; CHF, casein hydrolyzate formula; WHF, whey hydrolyzate formula; AAF, amino acid
formula.

Table 11.13  Management of infantile colic

Non-invasive
Rule out more serious medical conditions
Parental support and coping techniques
Soothing techniques
Eliminating tobacco smoke exposure (associated with
increased motilin/hypermotility)

Proposed interventions
May be trialed
Hypoallergenic diet
•  Formula-fed: hydrolyzed formula
•  Breastfed: maternal elimination diet
Sucrose
Probiotics
Safety needs to be assessed
Herbal tea
Anticholinergic drugs

a hypoallergenic diet, maternal elimination of
cows’ milk may be tried first, followed by soy if no
results are seen; as a last resort, other allergenic
foods such as wheat, peanut, tree nuts, fish and
shellfish may be eliminated. The effect of altering
the maternal diet on the duration of breastfeeding
should be addressed, and breastfeeding should be
encouraged for its many other benefits. For this
same reason, discontinuing breastfeeding and
switching a colicky infant to a hypoallergenic
formula may not be advisable when additional
research is needed and colic is considered a benign
condition.
It is recommended that alterations in diet be
undertaken as trials. If there is no improvement in
colic symptoms on a hypoallergenic diet, then a
regular diet can be resumed. A hypoallergenic diet
may be considered beneficial if symptoms improve
or resolve when suspect foods are removed and
159

Food Allergy

recur when they are reintroduced.60 Because colic is
self-limited and resolves in most infants by 4
months of age, and because many children outgrow
early food intolerances, rechallenges with suspect
foods may be attempted every 3–4 months with
physician recommendation.60

Summary
We have reviewed the common childhood non-IgE
mediated gastrointestinal conditions induced by
food proteins. The prognosis is favorable, with the
majority of cases resolving in the first few years of
life. Diagnosis is complicated by the lack of noninvasive confirmatory tests and tests that identify
the offending food proteins. Definitive diagnosis
usually requires an oral food challenge. Management relies on the avoidance of the offending food
and periodic reintroductions.

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43. Isolauri E, Turjanmaa K. Combined skin prick and
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67. Iacono G, Carroccio A, Montalto G, et al. Severe
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77. Kanabar D, Randhawa M, Clayton P. Improvement of
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81. Moore DJ, Tao BS, Lines DR, et al. Double-blind
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102.

103.

104.

105.

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Pediatrics 1991;87:623–30.

163

CHAPTER

12 

Approach to the Clinical Diagnosis
of Food Allergy
Jonathan O’B. Hourihane

Introduction
Clinical history-taking remains the cornerstone of
diagnosis of food allergy, as it does for all other
medical conditions. Distinguishing different phenotypes of food allergy can be a simple task, for
example a parental report of the onset of urticaria
and angioedema 2 minutes after eating peanut
butter, or it can be very difficult, for example distinguishing eosinophilic esophagitis from gastroesophageal reflux disease (GERD). The experienced
clinician can use existing knowledge of allergy
syndromes to distinguish a particular child’s current
allergic status, the likelihood of resolution of the
index food allergy, which may require proof by
formal challenge, and can give some guidance
about the breadth and duration of the required
exclusion diet.
The discriminating use of in vivo and in vitro
diagnostic tests relies on an understanding of the
relevance of a particular history and their usefulness in any particular population. Their sensitivity
and specificity are related to the pre-test probability
of a disease being present in the population being
tested. As an example, the significance of a positive
skin prick test (SPT) to hazelnut of 3 mm differs
between a 12-month-old child who has suffered
anaphylaxis after eating hazelnut spread and a
12-year-old child who is having allergy tests for
rhinitis but has probably eaten hazelnut several
times before.1
© 2012, Elsevier Inc

The skill of history-taking related to specific food
allergy syndromes or scenarios means that tests,
when performed, can be interpreted in a more discriminating and definitive manner. It is therefore
worthwhile examining how a physician’s assessment of children presenting with suspected food
allergy and his/her subsequent management of the
condition(s) vary as a function of the interaction
between the discrete or related foods and the child
as he or she grows from being exclusively dependent on breast milk or infant formula, via weaning
onto a narrow range of foods, and eventually onto
a fully diverse and unrestricted ‘adult’ diet.

First consultation
This is a critical moment for families, and attention
must be given to both the medical details and the
family’s response to what happened to their child
that prompted their attendance. It might have been
anaphylaxis, which they did not recognize, or it
might have been urticaria that they have attributed
to a previously tolerated food, but which was in
fact not related to allergies at all. Most families will
have received advice from family members or will
have searched the internet before their appointment with an allergist. Some of this information
may be correct, but experience shows that dietary
eliminations/exclusions may be too broad; the
child may be undernourished, or might be living

Food Allergy

on an age-inappropriate diet due to concerns about
trying new foods.

CLINICAL CASE

Other conditions can mimic
food allergy
An 11-month-old girl developed urticaria and swollen
lips 2 hours after eating boiled egg. This resolved
without treatment. She had previously tolerated one
teaspoon of less-cooked scrambled egg. At 1 year of
age she developed a cough and temperature, with a
maculopapular rash (Fig. 12.1). On waking the next day
she had urticaria on her legs (Fig. 12.2). No new foods had
been introduced, and she had not been given any form of
egg again.
Skin prick testing and serum-specific IgE at 13 months
were both negative for egg. A diagnosis of virus-induced
urticaria was made and she was discharged from
follow-up.

Figure 12.1  A maculopapular rash seen on day 1 of a viral
illness. This is unlikely to be allergic in nature.

Figure 12.2  Urticaria seen in the setting of a viral illness is
more likely to be due to the viremia than to a new allergy to a
food previously tolerated.
166

Several features of this story suggest a non-allergic basis
of her symptoms. This girl’s initial cutaneous reaction
was slightly delayed at 2 hours after contact with
well-cooked egg, and she had previously eaten a less
well-cooked (therefore more allergenic) form of egg
without complication. The onset of a typical exanthem
in the setting of fever, followed by urticaria, made it
straightforward to diagnose virus-induced urticaria. The
tests for egg allergy may not even have been necessary.

Mast cell membrane-bound IgE is not the only
mechanism of degranulation of mast cells. Complement activation can also cause mast cell deg­
ranulation, and mast cells can respond to C5A
stimulation, neurogenic stimulation and hormonal
influences. Although hormonal influences are relatively irrelevant in small infants, they have high
relevance in adolescent girls and may be related
both to menstruation-related urticarial syndromes
and also to exercise-induced anaphylaxis, with or
without a food trigger.
As infants may be committed to the allergic
march (see Chapters 3 and 18) for their entire
childhood or longer, the pediatric allergist must
ensure that he understands and addresses families’
concerns; that he can remove unnecessary dietary
and social restrictions; and that families remain
engaged with the medical allergy service until the
allergy issues are resolved or appropriate selfmanagement strategies are in place for adolescents
and young adults. For example, negative skin pricks
(high negative predictive value; see Chapter 13) can
be very useful in encouraging parents to relax
unjustified restrictions on their child’s diet.
Even at first consultation it is important for families to realize that an allergological evaluation is
as much about which foods a child can be allowed
to eat as about which they must rigorously avoid.
A fundamental part of the clinical management of
food allergy is to ensure that all foods that should
be excluded are excluded, and that foods that do
not need to be excluded are included, even at the
time of diagnosis. An example of prudent exclusion is to advise parents that children with cows’
milk allergy should not be exposed to goats’ milk.
The child must avoid the index food – in this case
cows’ milk – as reactivity is likely to be still present
at first consultation, and must also avoid the associated food – goats’ milk – which is highly crossreactive with cows’ milk, occasionally causing
anaphylaxis in children whose presenting allergic
reactions to cows’ milk have only been mild.2,3 If a
child has already been exposed to goats’ milk

Approach to the Clinical Diagnosis of Food Allergy

12

Table 12.1  Even at first consultation, some prudent inclusions and exclusions can be advised by
an experienced allergist

Index food allergen,
to be avoided

Food that should be prudently
excluded, unless known to have
been consumed safely

Food that can be prudently included,
if not previously consumed safely

Cows’ milk

Goats’ milk

Unadulterated egg

Raw egg (mayonnaise, fresh ice cream)

Baked egg (cakes, muffins)
Peanut*

Peanut

Tree nuts†

Other legumes, incl. soya
Coconut, nutmeg‡

Cod

Other white fish

Tuna∫

Sesame

Peanut

*Only if negative SPT with peanut.
†Consider open challenge if positive.
‡These foods are not nuts or legumes (peanut is a legume).
∫ Canned tuna is tolerated by most children allergic to white fish.

without incident, then it is reasonable to allow
prudent consumption of goats’ milk products,
although goats’ milk is neither a perfect nor nutritionally complete substitute for cows’ milk.
An example of early prudent inclusion is allowing continued consumption of baked egg products
in children who have previously eaten them safely
but have reacted to less well-cooked egg. Elimination of all egg products can be common in this
scenario, but in fact safe consumption of baked egg
products appears to modify the in vitro immunological profile of such children, making it more
similar to those of children proven tolerant to egg
than to children who remain allergic to less wellcooked egg.4 On a practical note, the avoidance of
less well-cooked egg is much easier than avoiding
baked egg products, so this small liberation of an
avoidance diet can have a big, early impact on
family life, even while maintaining avoidance of
the implicated form of egg (Table 12.1).

What immune mechanism is causing
the problem in this child?
IgE is found in all body compartments, so IgEmediated reactions often manifest in more than
one body system. It is still uncertain how a locally
initiated IgE-mediated reaction to a very small
oral dose of food allergen becomes amplified
into a multisystem reaction or even anaphylaxis.

Figure 12.3  This 4-month-old boy had suffered eczema since
his third day of life. He failed to thrive on breast milk, but was
not brought to medical attention by his parents, who are nurses.
He was offered his first infant formula at 4 months. Ten minutes
later he had facial erythema, angioedema and wheeze, and was
referred to hospital. Milk elimination and topical skin care were
initiated as an inpatient and he is now eczema free at 7 months,
on an amino acid formula and a milk-, egg- and wheat-free diet.

Similarly, it must be recognized that delayed
cell-mediated responses can coexist with immediate IgE-mediated responses. So there are overlap
syndromes including children who suffer both IgEmediated, early symptoms relating to milk ingestion, and also delayed, cell-mediated reactions to
milk in the forms of exacerbations of eczema or
atopic dermatitis (Fig. 12.3 and Chapter 5).
167

Food Allergy

Similarly, there are many infants whose parents
report that dairy products and egg make their
eczema worse but who have never suffered from
urticaria or angioedema. Occasionally these infants
and young children can tolerate small amounts of
dairy, e.g. half a pot of infant yoghurt per day, but
not more than this amount on a regular basis. This
scenario suggests a delayed-onset reaction that is
cell mediated and very unlikely to evolve into anaphylaxis. The prognosis for this type of milk allergy
is generally more favorable than for IgE-mediated
immediate reactions.
There are common diseases that can mimic food
allergy, such as gastroesophageal reflux disease
(GERD), which can cause difficulty with feeding
and vomiting but is not usually associated with
urticaria or angioedema. Eosinophilic esophagitis
(Chapter 10) has an overlap with GERD and the
diagnosis of eosinophilic esophagitis cannot be
confidently made until a child has failed a trial of
proton pump inhibitor.5

CLINICAL CASE
A 10-year-old boy relocated from another country where
he had been under the care of an allergist since the
age of 3 years, when he had apparently suffered a
life-threatening reaction to banana. He had been on amino
acid formula in early infancy for severe eczema and GERD.
Formal food challenges had liberated restrictions related
to asymptomatic peanut and tree nut sensitization. At his
first interview after relocation he reported lifelong
abdominal and retrosternal pain and excessive burping
after eating eggs, most fruits and vegetables. SPT was
positive for egg and kiwi, but negative for soya, carrot,
corn, sweet potato and wheat. Because of the combination
of lifelong history of feeding difficulties, and of atypical
reactivity to foods that are both commonly and
uncommonly seen as allergens, it was suspected he might
have eosinophilic esophagitis. In a reductive way his
symptomatology seemed more explicable as an intrinsic
inflammatory problem in his GI tract than atypical allergic
reactivity to multiple foods. Endoscopy confirmed the
diagnosis (Fig. 12.4). A 6-week trial of proton pump
inhibition failed to improve his symptoms, but formal
exclusion of implicated foods, supported by dietetic
review, remains successful.

Which foods are common allergens
in this age group?
There is much practical merit in breaking down
the description of clinical diagnosis into age-related
groups, because there is a chronology to the
168

Figure 12.4  Biopsy from the mid-esophagus showing
abundant eosinophils (> 15/hpf).

associations between food and different clinical
manifestations of food allergy.

Suspected allergic reactions under
6 months of age
The atopic march or marathon is well established
and often starts with food allergy and eczema in the
first 6 months of life (see Chapters 3 and 18). Urticaria and angioedema are unusual initial presentations of cows’ milk allergy in breastfed infants who
usually have enteropathic and dermatological
manifestations. However, the introduction of cows’
milk formula is often associated with urticarial
reactions in symptomatic cows’ milk-allergic
infants. The reasons for this are unknown, but may
be related to the presence in breast milk of immunomodulatory factors, or because the dose of allergenic cows’ milk proteins is naturally higher in
directly administered cows’ milk-based infant formulae than in human breast milk.
Exclusion diets during pregnancy or breastfeeding are no longer recommended as protection/

Approach to the Clinical Diagnosis of Food Allergy

prophylaxis against developing allergic disorders,6,7
but they can be very successful in reducing or even
eliminating cutaneous and other reactions in allergic children who have demonstrated clinical reactivity during breastfeeding.

Diagnosis and therapy can
proceed simultaneously
A trial of maternal dietary elimination can also be
part of the clinical diagnostic process as it can identify whether one food, more than one food, or any
food at all, is actually implicated in the condition
being presented in a breastfed infant. Professional
supervision by an allergy-experienced dietitian is
essential. Persistence of symptoms on a properly
supervised elimination diet adhered to by the
mother means that those foods are not the cause of
the skin or GI symptoms and the foods can be
reintroduced carefully, one at a time. It has been
reported occasionally that severe reactions can be
elicited during the reintroduction of excluded
foods, but this is not common in breastfed infants.
The diagnostic and therapeutic dilemma then
remains whether to empirically exclude a second set
of foods on the same trial basis, or to abandon
dietary exclusions completely. Experience shows
that as the first-rank foods excluded (milk, egg,
wheat, soya) are responsible for the vast majority of
food-related enteropathic and skin symptoms in
breastfed infants, a second trial of other empiric
exclusions may not be successful, unless a particular
food consumed by the mother can be implicated.
As time passes the relative nutritional importance
of breastfeeding diminishes for children in developed countries, and the introduction of supplemental feeding with extensively hydrolyzed or
amino acid-based infant formulas may reduce child
and maternal distress considerably. This allows
parents to see that their baby can grow and sleep
peacefully after feeding, and can reassure them sufficiently to introduce other foods at home.
In early infancy – under 3–4 months – other food
allergy syndromes can be confused with cows’ milk
allergy or other malabsorptive conditions. Cows’
milk protein enterocolitis and proctitis can present
simply with bright red blood in the diaper. These
easily identified children are not unwell and
respond very quickly to substitution of cows’ milk
with extensively hydrolyzed or amino acid formulas. IgE-based tests are usually negative and endoscopy is not required in the simplest of cases. Other

12

infants may develop food protein enterocolitis syndrome, which is a much more complicated disease
to diagnose and treat than IgE-mediated food
allergy (see Chapter 11). These children can present
insidiously with intractable enteropathy/diarrhea
and failure to thrive, or catastrophically in a collapsed state such as cardiogenic shock, due to
massive GI fluid loss. The latter responds well to
high-volume fluid resuscitation. In such presentations it may not be appreciated that there may be
a connection with food, as the collapse may be
several hours after ingestion of the food. Rice, soya,
cows’ milk and wheat are the most commonly
implicated foods in this condition.8

Suspected allergic reactions to
foods 6–18 months
Weaning foods are usually introduced one at a
time, even in non-allergic children, so linking
suspected exposure to a witnessed reaction is not
difficult. Common weaning foods are usually vegetables, fruits, and cereals such as wheat and oats.
Wheat is a common allergen, and is an ingredient
that must be labeled according to EU law. Wheat
allergy, however, is much less common than milk
or egg allergy, so it is worth investigating the implicated meal for hidden dairy products, as many
weaning foods have milk powder in them. Furthermore, the interpretation of positive tests for IgEmediated wheat allergy is more difficult than for
milk, egg and peanut (see Chapter 13). Like egg and
milk, wheat commonly causes delayed cutaneous
reactions, such as a flare of eczema. For reasons that
are based on both sound immunological principles
(wheat is known to cause both immediate, IgEmediated and delayed, cell-mediated symptoms)
and on experience (IgE-based tests can be unhelpful
even in immediate reactions to wheat), a supervised
early food challenge in hospital is often more
worthwhile for wheat (and soya for the same
reasons) than for milk and egg.
Eczema is a very common disorder in infants, and
parents can report that some foods cause deterioration in eczema both in the perioral area and at
more remote sites. There is a strong association
between eczema of more than moderate severity
and food allergy.9,10 However, many suspected
foods are acidic fruits, and it appears that the flare
of local and distant eczema is due to a directly
irritant effect of the acidic juice on the damaged
skin barrier. Skin prick testing might be needed, as
169

Food Allergy
Table 12.2  Acidic foods can cause a flare of facial
eczema that is often suspected to be allergic in origin
Kiwi*
Strawberry, raspberry etc*
Tomatoes*†
Citrus fruits (orange, lemon, lime)
Vegetable/yeast spreads (Marmite, Vegemite) (common in
UK, Australia only)
*Can also cause IgE-mediated reactions, so SPT can be undertaken.
†Usually raw tomato only, with cooked tomato tolerated.

some first- and second-rank food allergens (kiwi
and tomato in particular, but also strawberry) can
also act in this way, so it can be prudent to do skin
prick testing to demonstrate to families that the
reaction is not likely to be IgE-mediated and is
therefore likely to be benign and to resolve over
time, when the skin barrier, especially on the face,
has become better established (Table 12.2).
The introduction of other foods after weaning has
started can implicate them in allergic reactions.
Known allergenic foods such as lentils, hazelnuts
and peanuts (in spreadable butter form rather
than as whole or crushed nuts) can be introduced
in this age group, but the diagnosis of allergy to
these foods is usually made easily, as these foods
are predominantly associated with stereotypical
IgE-mediated reactions. Egg can again be implicated, in the form of boiled egg, pancakes, or raw
or nearly raw in mayonnaise or ice cream, even if
cooked egg has already been introduced without
complication.

International and intercultural
considerations
Individual foods can ‘behave’ differently at weaning
in different geographical locations, possibly related
to whether sensitization has happened de novo
with the native food or secondarily via pollen allergens that are highly cross-reactive with food allergens. Hazelnut allergy is the archetype of this11 (see
also Chapter 7).
Weaning practices vary internationally too: lentils
are a common weaning food for children in southern Europe but not in northern Europe. The exception to this observation is in families who are
vegetarian for personal, cultural or religious reasons.
Indians and Pakistanis living in northern Europe
170

are commonly vegetarian, and allergenic legumes
including lentils and chick peas are staple weaning
foods for infants, and are part of the family diet for
older children and adults alike. Scandinavian families may introduce fish earlier than more southerly
populations, and fish allergy was first well described
in Scandinavian infants. Children of West African
and Far Eastern families may consume boiled
peanuts, considered to be less allergenic than
roasted peanuts. Israeli Jewish children have peanut
introduced to their diet much earlier than Jewish
children in Britain, which has been suggested as
part of the reason for a much lower prevalence of
peanut allergy in the former group, though other
differences in allergic conditions between the
groups cannot be accounted for by the timing of
introduction of peanut.12

New food allergies after infancy
Regular longitudinal review of existing allergies
also needs to consider whether allergies established
and diagnosed in infancy are persisting or have
resolved (see Chapter 14 regarding the selection of
children for challenge, and when and how to
perform challenges). After infancy, children may
encounter ‘their’ known allergenic foods sporadically or accidentally. Contrary to popular belief,
these accidental exposures do not automatically
lead to a worsening of the allergic reaction. It is
more likely that variation in reaction severity is due
to cofactors such as relative dose, asthma status,
and the coexistence of viral infection or stressors
such as exercise.13 Such exposure may, however,
give a clue to the issue of resolution or persistence
of food allergies after infancy.
The onset of new allergies after infancy is a reflection of a broadening dietary repertoire (for example,
peanut-allergic infants often develop allergy to tree
nuts). The occurrence of accidental exposure to
known allergens reflects a child’s independence
from (usually maternal) supervision. Although
there is accumulating evidence regarding minimal
eliciting doses for allergic reactions in allergic individuals,14 there are no strong clinical or experimental data regarding the circumstances surrounding de
novo sensitization in humans. Most data are derived
from animal models of allergic disease,15,16 so it is
hard to be dogmatic about the advice to give to
parents, beyond that outlined in Table 12.1 for
infants. Regular review will allow assessment of

Approach to the Clinical Diagnosis of Food Allergy

dietary introductions that have passed without
incident and those that have elicited allergic
reactions.
Approximately 20% of egg-allergic children demonstrate IgE sensitization to peanut.17 At this high
rate, case finding (rather than screening) of peanutsensitized children in an egg-allergic population
with a peanut SPT or specific IgE test is worthwhile.
The emergence of specific diagnostic tests for individual allergens may assist in distinguishing sensitization from likely allergy,18,19 but at present a
food challenge remains the only definitive test. This
means that a lot of egg-allergic children spend a
long time avoiding foods containing (or only possibly containing) peanut, to which they are sensitized but not allergic.
Other commonly allergenic foods are excluded
from infant diets for reasons unrelated to their
allergenicity. Peanuts and tree nuts are often consumed by infants in spread form, but peanut and
nut fragments have a long and notorious history of
accidental inhalation. Fish is often excluded from
the diet in early life due to the fear of fish bone
impaction. Shellfish (e.g. lobster) may be considered too expensive to be given to a child, who
might not eat it, but, other shellfish, both molluscs
and crustaceans, are available in easily deliverable
form, with no financial or structural limitations on
their use. However, it is not feasible to test all foodallergic children for even the major food allergens
before they first consume them. Pragmatic advice
must be given. As an example, unless a family is
receiving advice from a dietitian to avoid it, soya is
very difficult to avoid in prepared foods, such as
industrially produced bread and tinned foods. It is
therefore likely that it is already being tolerated by
most food-allergic children. Cross-reactivity of soya
with cows’ milk varies from <10% to 50% of cases
of cows’ milk allergy in infants. Peanut and soya
rarely cross-react, and peanut-allergic children
should not be advised to avoid soya unless reactivity to soya is already suspected clinically. In
contrast, other legumes may be problematic for
soya-allergic children but are rarely so for peanutallergic children. Egg-allergic children may not tolerate other avian eggs such as duck or goose, but
these are not staple or even remotely common
foods. Parents often ask about them in desperation
at the apparently hopelessly narrow repertoire of
foods that they can safely offer their child.
In practice, children adapt well to the limits on
their dietary variety, but it must be acknowledged

12

that there is a large impact on their overall health
status-related quality of life. Growing children
socialize and act more independently of their
parents, but food-allergic children must become
aware of the reasonable limits on their independence that comes with a diagnosis of food allergy.
Such children can develop extreme anxiety when
they encounter unfamiliar foods, or can experience
social isolation when excluded from activities such
as school outings and birthday parties.20 Birthday
parties and other social outings bring with them the
risks associated with eating food prepared by people
other than allergy-aware or hyper-aware parents.
Reasonable planning and communication between
the host parents and the food-allergic guest child
can eliminate or minimize disruption to the social
event (for further discussion see Chapter 15).
From a medical diagnostic perspective, new reactions in settings away from the family home can
represent a greater difficulty than reactions at home
in infancy. Ethnic cooking such as Chinese and
Thai is a known potential source of nut and seed
allergens. In restaurants and take away/carry-out
stores staff awareness of food allergies may be hindered by difficulties relating to language barriers
and level of education, the availability of allergyspecific food safety training and general food allergen hazard control practices.21 Families may need
to practice the advice ‘If in doubt, do not eat out’.

Diagnosis of new allergies
in adolescents
Older children may develop food sensitization
through inhaling allergens, such as the oral allergy
syndrome with birch, pollen and labile allergens in
apples and hazelnuts. These are usually easy to
manage on the basis of the clinical scenario relating
to oral allergy syndrome, with general benign reactions related to known foods in which crossreactivity between the food and the inhalant allergy
is either known or suspected (see Chapter 7).
It should be a major focus of dialog with adolescents and young adults that risk-taking with foods
is a real danger and that they are at much higher
risk of death from food allergy now than when they
were younger. Coexisting rejection of parental
supervision/advice/support/control and a desire to
both conform with a peer group and establish intimate personal relationships heighten food allergyrelated risk.22,23 Food-allergic adolescents may need
171

ce

ce

ce

ce

ce

ce

ce

ce

ce

ce

ce

Food Allergy

to be interviewed without their parents, as they may
have questions about personal relationships and
other aspects of their life with and without allergies.
Non-latex barrier contraception may be an issue for
subjects with kiwi–latex syndrome.

Diagnosis of new allergies in adults
This area is definitely the poor relation of pediatric
allergy, with few solid, challenge-proven epidemiological data to guide a diagnostic interview.24 Diet is
the most important acquired determinant of adult
health, and adults are free to choose what to eat in
a way that children are not: children’s parents make
food choices for them. However, adults with food
allergy may have even more difficulty than children
in accessing expert care for their allergies. Some may
have food allergies that have persisted since infancy,
such as peanut, or since mid-childhood, such as tree
nut, fish or shellfish, or they may have developed
oral allergy syndrome in adolescence.
When electively restricted diets have been
excluded, such as vegan diets, the assessment of a
suspected food-allergic adult must focus on whether
a recognized allergy syndrome is present or not.
Other conditions that are more common in adults
Remarks
than children may mimic allergic
disorders: these
include irritable bowel syndrome, wheat and milk
intolerance, and again the eosinophilic disorders.
Allergy to non-steroidal medication and the impact
of medication use on the outcome of allergic reactions are more relevant in adults than children.
Antihypertensive medications such as ACE inhibitors and β-blockers must be identified and alternatives considered in adults who have genuine
IgE-mediated allergies.

Conclusion
An astute clinician can glean a lot of information
from even the first encounter with a child or adult
who may have experienced an allergic reaction to
food. What has changed in the last decade, and
what is likely to be utterly transformed in the next
decade, is the amount of evidence-based information a family can be given at the same first interview. Clinicians and families embark on a health
journey together. The length of this journey and the
variety of possible final endpoints will continue to
motivate clinical allergists for many years to come.
172

References
1. Roberts G, Lack G. Food allergy–getting more out of
your skin prick tests. Clin Exp Allergy
2000;30(11):1495–8.
2. Pessler F, Nejat M. Anaphylactic reaction to goat’s milk
in a cows’ milk-allergic infant. Pediatr Allergy Immunol
2004;15(2):183–5.
3. Ah-Leung S, Bernard H, Bidat E, et al. Allergy to goat
and sheep milk without allergy to cows’ milk. Allergy
2006;61(11):1358–65.
4. Lemon-Mulé H, Sampson HA, Sicherer SH, et al.
Immunologic changes in children with egg allergy
ingesting extensively heated egg. J Allergy Clin
Immunol 2008;122(5):977–83.
5. Rothenberg ME. Biology and treatment of eosinophilic
esophagitis. Gastroenterology 2009;137(4):1238–49.
6. Greer FR, Sicherer SH, Burks AW. Effects of early
nutritional interventions on the development of atopic
disease in infants and children: the role of maternal
dietary restriction, breastfeeding, timing of
introduction of complementary foods, and hydrolyzed
formulas. American Academy of Pediatrics Committee
on Nutrition; American Academy of Pediatrics Section
on Allergy and Immunology. Pediatrics 2008;121(1):
183–91.
7. Department of Health. Revised government advice on
consumption of peanut during pregnancy,
breastfeeding, and early life and development of
peanut allergy. Revised August 2009. www.dh.gov.uk/
en/Healthcare/Children/Maternity/
Maternalandinfantnutrition/DH_104490
8. Nowak-Wegrzyn A, Muraro A. Food protein-induced
enterocolitis syndrome. Curr Opin Allergy Clin
Immunol 2009;9(4):371–7.
9. Hill DJ, Hosking CS. Food allergy and atopic
dermatitis in infancy: an epidemiologic study. Pediatr
Allergy Immunol 2004;15(5):421–7.
10. Hill DJ, Hosking C, de Benedictis FM, et al.
Confirmation of the association between high levels of
immunoglobulin E food sensitization and eczema in
infancy: an international study. Clin Exp Allergy
2008;38(1):161–8.
11. Hansen KS, Ballmer-Weber BK, Sastre J, et al.
Component-resolved in vitro diagnosis of hazelnut
allergy in Europe. J Allergy Clin Immunol 2009;
123(5):1134–41.
12. Du Toit G, Katz Y, Sasieni P, et al. Early consumption
of peanuts in infancy is associated with a low
prevalence of peanut allergy. J Allergy Clin Immunol
2008;122(5):984–91.
13. Hourihane JO’B, Knulst AC. Thresholds of allergenic
proteins in foods. Toxicol Appl Pharmacol 2005;
207(2 Suppl):152–6.
14. Taylor SL, Crevel RW, Sheffield D, et al. Threshold dose
for peanut: risk characterization based upon published
results from challenges of peanut-allergic individuals.
Food Chem Toxicol 2009;47(6):1198–204.
15. Strid J, Hourihane J, Kimber I, et al. Epicutaneous
exposure to peanut protein prevents oral tolerance and

Approach to the Clinical Diagnosis of Food Allergy
enhances allergic sensitisation. Clin Exp Allergy 2005;
35(6):757–66.
16. Lack G. Epidemiologic risks for food allergy. J Allergy
Clin Immunol 2008;121(6):1331–6.
17. Sicherer SH, Wood RA, Stablein D, et al. Immunologic
features of infants with milk or egg allergy enrolled in
an observational study (Consortium of Food Allergy
Research) of food allergy. J Allergy Clin Immunol
2010;125(5):1077–83.
18. Asarnoj A, Moverare R, Ostblom E, et al. IgE to peanut
allergen components: relation to peanut symptoms
and pollen sensitization in 8-year-olds. Allergy
2010;65:1189–95.
19. Nicolaou N, Poorafshar M, Murray C, et al. Allergy or
tolerance in children sensitized to peanut: Prevalence
and differentiation using component-resolved
diagnostics. J All Clin Immunol 2010;125:191–7.

12

20. King RM, Knibb RC, Hourihane JO’B. Impact of
peanut allergy on quality of life, stress and anxiety in
the family. Allergy 2009;64(3):461–8.
21. Leitch IS, Walker MJ, Davey R. Food allergy: gambling
your life on a take-away meal. Int J Environ Health Res
2005;15(2):79–87.
22. Sampson MA, Muñoz-Furlong A, Sicherer SH. Risktaking and coping strategies of adolescents and young
adults with food allergy. J Allergy Clin Immunol
2006;117(6):1440–5.
23. Marklund B, Ahlstedt S, Nordström G. Health-related
quality of life among adolescents with allergy-like
conditions – with emphasis on food hypersensitivity.
Health Qual Life Outcomes 2004;19(2):65.
24. Rona RJ, Keil T, Summers C, et al. The prevalence of
food allergy: a meta-analysis. J Allergy Clin Immunol
2007;120(3):638–46.

173

CHAPTER

13 

In Vivo and In Vitro Diagnostic Methods
in the Evaluation of Food Allergy
S. Allan Bock

KEY CONCEPTS
Skin prick or puncture tests to foods are very useful
when properly performed and interpreted.
 Negative prick/puncture skin tests have a high negative
predictive accuracy for many foods (>95% for the
common foods).
 Positive prick/puncture skin tests have a high positive
predictive accuracy for egg, milk and peanut in young
children, and the size of the skin test is relatively
predictive.
 Food-specific serum IgE antibodies for a few foods can
be used to predict the probability of a positive
challenge. ‘Cut-off’ levels for egg, milk, peanut and fish
mix have been established. There are also levels for tree
nuts that are helpful but not as accurate; however, they
are useful for deciding whether an individual should
have a food challenge (Fleischer has suggested a level


This chapter focuses on skin testing and in vitro
laboratory testing for food allergy. Chapter 14 discusses the ultimate gold standard, which is the oral
food challenge. It is this that has helped determine
the utility of the measurements discussed below.
The goal of this chapter is to give the reader choices
of methods depending on the setting, the training
of the practitioner and the child’s circumstances. Of
all the areas of medicine stressed in Chapter 12, the
history is the most important component of the
evaluation. Ultimately and ideally, the facts gathered will be used to try to reproduce the history to
confirm or refute the incriminated food as the
culprit.
© 2012, Elsevier Inc

below 2 kU/L as the level for deciding to do a challenge
depending on the history).
 Measuring the annual fall in the specific IgE level for a
few foods can help determine the likelihood of
resolution of the food allergy.
 Food challenges may be guided by the results of skin
testing and food-specific serum antibody level
determination, but these measurements have not
replaced oral food challenges. It remains to be
determined whether or not component-resolved
diagnostics can replace food challenges, or at least
predict that the probability of the food being tolerated
or triggering symptoms is very high.
 Patients should be followed annually as they get older
to determine the chance that food allergy has been
outgrown. This is an ongoing process.

Skin testing
Skin testing is a technique that has been employed
for decades and has been used with apparent confidence for testing aeroallergens. However, 30 years
ago there were questions about the usefulness of
allergy skin testing for food allergy. Part of this
confusion stemmed from the fact that patients were
often told that they had positive skin tests to foods
that they knew they could eat without experiencing
adverse clinical symptoms. This confusion did not
seem to be as troublesome when patients with a
positive skin test to cat found they could sleep with
the cat without symptoms. Why the difference? It

Food Allergy

Hx distant reaction (>6 mos)

Hx recent reaction

Skin test

Skin test

ST Pos

ST Neg

sIgE

sIgE

Above cut-off level:
avoid food 1 year
then repeat

Below cut-off:
challenge

Above cut-off:
avoid food, repeat
in 1– 2 years

ST Neg

ST Pos

sIgE

Below cut-off:
challenge

Above cut-off level:
avoid food 1 year
then repeat

Challenge
negative food
in diet

Challenge positive,
avoid and repeat
1–2 years

Figure 13.1  Algorithm for older subjects, >5 years of age – take a detailed history, be certain to determine most recent reaction
with symptoms and severity. Levels most helpful for egg, milk, peanut and tree nuts.

may be that because you can see what you eat, food
allergy testing resulted in more confusion. This is a
strong argument for using an approach that only
tests for foods under suspicion, rather than panels
of foods (i.e. the same argument is true for measurement of serum antibody levels) as discussed below.
With regard to the specific testing method used,
it is generally agreed that the ‘prick/puncture’ skin
test gives the most accurate and helpful information regarding food allergy. However, there is not
universal agreement about the technique to be
used. Glycerinated extracts are available for many
foods in 1 : 10 or 1 : 20 weight/volume dilutions.
These are applied to the skin accompanied by positive (histamine) and negative (diluent-saline or
other solution used to mix allergen extracts) controls. The skin is then pricked or punctured with
one of several devices available. There are also a
number of devices that are preloaded with the
extract which are then applied to the skin. Skin tests
are usually read 15–20 minutes after they are
applied. Food allergen extract responses are considered positive when they elicit a wheal of 3 mm
larger than the negative control; smaller responses
are considered to be negative.
176

When skin tests are negative for several foods that
have been well studied, they have a very high negative predictive accuracy (approximately 95% for
children over 3–4 years of age) and in children
older than 2 years the negative test essentially eliminates the food as a culprit in triggering immediate
hypersensitive symptoms. These foods include egg,
milk, wheat, peanut, most tree nuts and soy. Data
for other foods are not quite as certain, but in
general a negative skin test makes an immediate
allergic reaction to food unlikely. However, it must
be emphasized that no test can ever confidently
contradict an unequivocal history, and care must be
exercised in this regard (Figs 13.1 and 13.2).

CLINICAL CASE
A 2-year-old girl is seen by an allergist for possible egg
allergy. The father reports that at about age 14 months
she was given some scrambled egg and developed a few
hives on her face. There might have been a few hives
on the abdomen. There were no gastrointestinal or
respiratory symptoms, but the father recalls that she
stopped eating the egg after a few bites. Prior to the
reaction she had consumed egg-containing baked goods
without problems. Since the urticarial reaction she has had
no egg and very little, if any, egg-containing food. The

In Vivo and In Vitro Diagnostic Methods in the Evaluation of Food Allergy

Hx distant rxn (>6 mos)

Hx recent reaction

Skin test

Skin test

ST + hx
confirmed

ST Neg

sIgE

ST Pos then
hx confirmed

ST Neg

Avoid food 1
year then repeat

sIgE

Below cut-off:
challenge

Above cut-off:
avoid food, repeat
in 6– 12 months

sIgE
undetectable
(and neg ST)

13

Incr sIgE, hx
confirmed for the
present, repeat
6–12 months

For egg, milk
consider challenge
in 3 – 6 months

Key for algorithms
ST pos = positive skin test
ST neg = negative skin test
sIgE = food specific IgE levels as measured in serum
For interpretation of sIgE levels see Tables

Figure 13.2  Algorithm from birth to age 3 for egg and milk – take a detailed history!
allergist performs an egg skin test with appropriate
controls and finds that it is negative. Because of the
history, egg-specific serum antibody levels are ordered
and are found to be undetectable. The allergist schedules
a food challenge, and after the equivalent of about one
slice of hard-boiled egg the child breaks out in hives on
her face and within a few minutes they spread to her trunk
and extremities.
This scenario raises a number of important points. The first
is that the history is confirmed by the food challenge. The
second is that the skin test and the serum antibody level
did not demonstrate sensitization that was confirmed
by the challenge. The third is that if the egg-specific
serum antibody level had been ordered and found to be
undetectable, and if the parents had been told to feed this
child egg at home, then there would have been a call to
the doctor and perhaps an urgent visit to the emergency
department. Even though the probability of this scenario
might be less than 10%, the most conservative approach is
always the best way to avoid unexpected outcomes.

The converse is not true. The positive predictive
accuracy of a positive skin test is often less than
50% for most foods, depending on the population
under study. Even for peanut allergy in unselected
populations (i.e. not stratified by history taken by
a knowledgeable allergist) the response rate to food

challenges is often less than 50%. A crucial understanding for healthcare providers and especially for
patients is that a positive skin test only detects the
presence of IgE antibody alone: it does not make a
diagnosis of clinical allergy (this is also true for
serum antibody levels, see below). In fact, a positive
skin test or detectable antibody is common in large
unselected populations and confirms sensitization
that may be asymptomatic.1–4 However, when there
is a history of a severe allergic reaction or anaphylaxis to an isolated food ingestion and the skin test
is positive, then the positive test may be viewed as
diagnostic without the need for further allergy
testing. There have been rare reports of adverse reactions to skin prick tests, but interestingly these have
almost all been to aeroallergen extracts.5 For allergists concerned about adverse reactions to skin
testing, it is easy to dilute commercially available
skin test extracts and use the dilutions for titrated
skin testing. There is even some preliminary evidence that dilution titration skin tests might be
used to enhance the predictive accuracy of food
challenges.6
In children less than 3 years of age the negative
predictive accuracy is not as high as in older
177

Food Allergy

children, and is probably in the range of 80–85%.
However, in this age group the positive predictive
accuracy of skin testing is very useful for egg, milk
and peanut. In children less than 2 years of age,
Hill’s group7,8 has reported that for these foods (and
only these three foods) a wheal of >8 mm is diagnostic of clinical reactivity in 100% of subjects who
were challenged. By contrast, Wainstein et al.9
reported that skin prick test wheals >8 mm had a
somewhat lower specificity, and cautioned that tests
may need to be interpreted in the context of specific
patient populations. A reasonable and practical
method by which to proceed is to take a careful
history, including seeking food aversions in young
children, and to pay close attention to positive skin
tests while being careful not to dismiss negative tests
in this age group, especially those that contradict
the history. After a complete history has been
obtained (Chapter 19), the skin tests to be applied
should be selected based on these details. As part of
this selection it is useful to categorize children by
age and history and then apply the known evidence
base to the selection and results of skin testing.
Kagan10 evaluated 47 children with a positive skin
test to peanut extract (i.e. wheal diameter > 3mm)
but no known history of reaction or accidental
ingestion. In this group, 23 (49%) of the challenges
were positive, inducing various symptoms. It is
crucial to note, therefore, that half of the challenges
were negative, and if the skin test alone was used
to prescribe dietary restriction of peanut, then all of
these children would be unnecessarily deprived of
peanut consumption. There are numerous important issues accompanying peanut exclusion diets
that alter quality of life at school, at home and in
the community. Among these are the prescription
and carrying of self-injectable epinephrine. Therefore, this study emphasizes the importance of not
relying solely on this skin test or in vitro foodspecific serum antibody levels.
Another common issue is whether the presence
of one food allergy indicates the existence of
others, especially in young children whose diets
have not yet included some common food allergens. Dieguez11 used skin prick tests to examine
children with diagnosed milk allergy to see if any
of them were sensitized to egg. They found that a
number of them were, and so recommended that
this group be carefully followed for the development of egg allergy. This observation then requires
evaluation for symptomatic egg allergy as well as
the possible resolution of milk allergy. Therefore, as
178

they get older children exhibiting this constellation
of positive skin tests will require ongoing (longitudinal) skin testing, food-specific serum antibody
level measurements and food challenges. Furthermore, allergists often skin test milk- or egg-allergic
children for peanut and tree nuts, and if positive
these foods will also require ongoing evaluation.
These observations reinforce the recommendation for choosing food extracts for skin testing
based on the history rather than a panel of food
skin tests or serum antibody levels. In very atopic
children (e.g. children with atopic dermatitis) the
more tests performed the more likely there are
to be numerous positive results requiring systematic evaluation. Although it may be appropriate to
do skin tests for foods not yet ingested in young
children, healthcare providers should seek to use
the best evidence base available to be judicious
about these choices (Fleischer et al., unpublished
observations).
Although allergen extracts have improved over
the years, some are more reliable than others. Allergen extracts for the major foods – egg, milk, peanut,
tree nuts and some grains – can be manufactured
so that they give predictable and reproducible
results in skin testing procedures. It remains incumbent upon clinicians to be certain that each lot of
extract contains active allergens. As there are several
manufacturers, verifying each new lot of extract that
is placed into use becomes important. It is possible
to purchase a bottle of allergen extract that does
not contain enough material to be detected by
antibody, leading to a potential for erroneous
interpretation.
This reliability is especially an issue when using
extracts of fresh fruits and vegetables. These are
hard to produce so that they contain relevant
allergen­s and they may lack the relevant proteins
responsible for allergic reactions.12–14 A preferable
approach is to use fresh foods. This technique has
been referred to as the ‘prick-to-prick’ technique or
‘puddle’ test. For the former, the food of interest is
pricked and then the skin of the subject is pricked.
An attempt is made to ensure that there is material
from the raw food on the skin testing device. The
puddle test is performed by putting a drop of the
fresh food on the skin and then pricking through
it with an appropriate device. A variant of this
approach is to squeeze liquid from the fresh food
into a small vessel and then use a syringe to put a
drop of this material on the skin. The test device is
then passed through the drop into the skin using

In Vivo and In Vitro Diagnostic Methods in the Evaluation of Food Allergy

the usual prick/puncture method. It is often useful
to undertake these two procedures in duplicate. It
is also useful to have a negative control subject so
that irritant reactions can be distinguished from
true immunologic responses.
There are a number of other variables to be considered when performing skin prick tests. Skin
testing of surfaces that have been treated with
topical steroids for atopic dermatitis may induce
smaller wheals than tests performed on untreated
skin; negative skin tests with commercially prepared extracts that do not support convincing histories of food reactions should often be repeated
with fresh foods prior to concluding that food
allergen-specific IgE antibody is absent:15 this may
include skin testing with whole milk and whole egg
(and a challenge performed prior to returning the
food to the diet); and there is some evidence that
long-term high-dose systemic corticosteroid therapy
may reduce allergen wheal size. For nuts for which
there are no commercially available extracts (macadamia and pine nut are two examples), a mortar
and pestle may be used to grind them to a powder,
and they can then be mixed with diluent and
applied to the skin. Spices are another example of
important food allergens that need to be prepared
for use when the need arises. Use of these nonstandardized preparations is most helpful when the
tests are positive, especially if they confirm the
history. A negative test with a suspicious history
requires a food challenge before the food is returned
to the diet.
Despite these caveats, properly performed skin
tests remain a very sensitive and important tool for
evaluation of food allergy. They are very useful,
results are immediately available, quality control is
in the hands of the individual performing the test,
and they are more sensitive than in vitro assays. All
of these considerations make them very practical
and cost-effective.
A note should be added about intradermal skin
tests for foods. They have never been shown to
be useful when skin prick tests are negative for
the vast majority of foods. Recently, some early
data have suggested that individuals reacting to a
carbohydrate determinant rather than a food
protein will have a positive intradermal skin test to
the putative culprit.16,17 Research in this area is
ongoing, but for the vast majority of food proteins
the intradermal skin test adds no useful information and has been said to potentially cause more
adverse reactions than prick testing.

13

CLINICAL PEARL

VARIABLES TO CONSIDER WHEN
PERFORMING SKIN TESTS
• Skin tests should be interpreted with caution when
performed on skin that has been treated with topical
steroids. The wheals might be smaller than expected.
• Skin tests with commercial extracts that do not support
the clinical history may need to be repeated with fresh
foods. This may be true for milk and egg as well, and
some authors recommend the use of whole milk and
raw or cooked egg in skin testing procedures.
• Some foods such as spices and even some nuts will
need to be prepared from the whole food by the
allergist, as there are no commercially available
extracts.
• A negative test with a suspicious history requires a
food challenge before the food is returned to the diet
(see Clinical Case above).

In vitro testing
Many of the comments about skin testing also apply
to in vitro testing. The selection of tests should be
guided by the history, and learning to interpret the
tests in light of the history is crucial. In vitro tests
are referred to using several different terms, but
precision in terminology will help both practitioners and patients use and understand the results. The
term commonly used is ‘RAST’ testing. RAST is short
for radioallergosorbent test, which was one of the
first in vitro tests used for diagnostic purposes. The
term ‘radio’ stands for radioactive, in other words,
this was originally a test using radioactive tracer
technology. This is no longer the case: the current
tests are immunoassays and should be referred to
as such. The tests now use liquid or solid-phase
reagents. The test currently favored by specialists is
the Phadia Immunocap assay because it has been
subjected to research studies that correlate the
results with double-blind placebo-controlled food
challenges. The test measures the amount of circulating allergen-specific IgE to individual foods and
is reported in kilounits of allergen-specific IgE antibody per liter. (Laboratories also report the results
in ‘class levels’, but these results have not been
shown to be useful in clinical practice and should
be ignored in favor of the kilounit levels that have
been correlated with food challenges.)
Because blinded food challenges are the gold
standard for making a diagnosis of food allergy (see
Chapter 14), it is possible to increase the precision
179

Food Allergy

of this immunoassay for diagnostic purposes by
performing food challenges concurrently with
immunoassay measurements. With the use of a
combination of skin tests and serum immunoassays,
it is possible to reduce the number of food challenges that are needed. However, it is important to
note that these predictive values are only for a
limited number of foods, specifically egg, milk,
peanut, fish, and to some degree tree nuts.
Generally skin testing appears to be the most
sensitive test for the reasons discussed above, but
there is one study9 that supports the notion that
skin prick tests and immunoassays have similar sensitivities and specificities. There are circumstances
in which in vitro measurements may be preferred.
These include patients with extensive dermographia; patients with extensive skin disease (atopic
dermatitis or generalized urticaria); patients who
for varying reasons cannot discontinue the use of
antihistamines; and the lack of availability of skin
testing in areas without allergy specialists.
The first demonstration of the utility of serum
antibody levels for managing food allergy came
from two important studies by Sampson,18,19 one
retrospective and one prospective. Using the CAPRAST Fluorescent Enzyme Immunoassay (the pre­
decessor to the current test) he demonstrated that
quantification of food-specific IgE provided helpful
predictive accuracies for egg, milk, peanut and fish
compared to skin prick testing. These studies were
meticulously performed using double-blind food
challenges, skin testing and food-specific serum
antibody levels. These were the first studies to establish cut-off levels that established 95% predictive
values, and these levels have then been used to
obviate the need for many food challenges. It is
important for clinicians to note that these measurements are 95% cut-off levels and individuals with
higher levels may be clinically non-reactive when
culprit foods are eaten. The converse is that
CLINICAL TEACHING POINTS

PREFERENCE FOR IN VITRO TESTS
VS SKIN TESTS
• Patients with extensive dermographia
• Patients with extensive atopic dermatitis or generalized
urticaria
• Patients who cannot discontinue antihistamines
• Areas where there are no allergists to perform skin
testing

180

individuals with serum antibody levels less than the
95% cut-off values may still have reactions and
should be cautioned against considering it safe to
ingest suspected foods. Subsequent studies have
attempted to establish lower levels of predictive
accuracy, but there is no level below which it is
certain that a reaction will not occur. Recent studies
suggest that monitoring the allergen food-specific
IgE values may be useful in predicting when individuals have ‘outgrown’ their specific food allergy
and therefore food challenges are appropriate and
likely to be negative.20 In young children it has been
shown that the ‘cut-off’ levels are lower for milk and
egg, but there are important exceptions in all of these
studies that relate to the population under consideration and the prevalence of the condition (Table
13.1).21–23 The food-specific IgE determinations may
be used prospectively in order to determine when
food challenges might be appropriate in children
who have been maintained on restricted diets.
Shek et al.24 have reported that the rate of fall of
the food-specific serum antibody level may be a
good predictor of when challenges are appropriate
for hen’s egg and cows’ milk. Recent studies have
also supported the contention that lower levels of
food-specific antibodies are associated with earlier
resolution of food allergy, suggesting that some
children have a different phenotype (and perhaps
genotype) of their food allergy than children with
Table 13.1  Predictive value of food-specific IgE

Allergen
Egg
  ≤ 2 yrs old
Milk
  ≤ 2 yrs old

Decision
point (kUA/L)
≥ 7.0

Rechallenge
value
≤ 1.5

≥ 2.0
≥ 15.0

≤ 7.0

≥ 5.0

Peanut

≥ 14.0

Fish

≥ 20.0

Tree nuts

≥ 15.0

≤ 5.0
< 2.0

Notes:
1.  Patients with food-specific IgE values less than the listed diagnostic
values may experience an allergic reaction following challenge. Unless
history strongly suggests tolerance, a physician-supervised food
challenge should be performed to determine whether the child can
ingest the food safely.
2.  These are values that have been derived from a number of studies;
these offer a practical approach to use of levels to determine whether
or not challenges should be done. There have been other studies
proposing other levels.

In Vivo and In Vitro Diagnostic Methods in the Evaluation of Food Allergy

13

Table 13.2  Suggested interpretation of food-specific serum immunoassay levels using one specific technique.
Created with the generous assistance of Staffan Ahlstedt PhD

Level undetectable: <.35 kU/L by ImmunoCAP for any individual suspected food:
Food allergy has a lower probability but must be considered in context of the history.
If there is a strong/suspicious history, refer to an allergist. Also consider other causes of symptoms. (Be careful not to tell
patients that the test is negative – antibody is undetectable, the test is not negative. Be extremely careful about allowing
food reintroduction at home when the history suggests a reaction has occurred.)

Level to one or more allergens: 0.35–5 kU/L by ImmunoCAP:
Possible reaction to food culprits.
Each allergen with a detectable level must be considered individually to be a trigger of symptoms.
If the history and the serum antibody level support each other, then avoid the food, educate the patient, parents, family
members and caregivers, and prescribe self-injectable epinephrine if indicated.
Then schedule regular review of course, accidental exposures, and periodically repeat the serum antibody levels (perhaps
annually).
At some interval after the last reaction (a year or more, depending on the age of the patient) consider referral for food
challenge under observation.

Level to one or more allergens: 5–15 kU/L by ImmunoCAP:
Significant probability of reaction.
Avoid each food, educate the patient, parents, family members and caregivers, and prescribe self-injectable epinephrine if
indicated.
Repeat the ImmunoCAP level every 1–2 years to see if it has fallen low enough to justify referral for possible challenge.

Level to one or more allergens: >15 kU/L:
For the major food allergens egg, milk, peanut, and possibly tree nuts there is very high probability of reaction.
Avoid the food, educate the patient, parents, family members and caregivers, and prescribe self-injectable epinephrine if
indicated.
Repeat the ImmunoCAP every 1–2 years to see if it has fallen low enough to justify referral for possible challenge.
When in doubt leave it out and arrange for a food challenge under observation in a safe place.
Remind patients/parents to practice using the self-injectable epinephrine so they can respond quickly and effectively
in a crisis!

higher levels.25–28 These observations make it imperative that the clinician ordering and interpreting the
test have sophistication in this area to determine
when challenges are indicated, safe, and likely to be
negative, in order to shorten the duration of elimination diets. Table 13.2 presents one approach to
interpretation. There are certainly others, and individual circumstances must always be taken into
consideration. However, the most important caveat
is that it is never acceptable to send individuals
home to reintroduce a food into the diet when the
history contradicts the skin tests and/or the foodspecific serum antibody level. Proper precautions
and warnings are always necessary before the
reintroduction of suspected food culprits away
from medical facilities.
The studies cited above apply primarily to allergies
to milk, egg, peanut, to some extent fish (but individual fish have not been examined in detail), and
less so to soy and wheat, for which Sampson did not
identify useful predictive values. More recently,

several investigators have determined that cut-off
levels for tree nuts, if interpreted judiciously, are
useful in accomplishing the goal of appropriate
dietary restriction and determination of the timing
of food challenges to nuts.29–32 Although these
studies are not as meticulous as the Sampson retrospective study that involved a food challenge for
every level measured, they do provide practical clinical data to use in the management of individual
patients. Fleischer’s studies propose that for levels of
tree nut allergens <2 kU/L challenges could be reasonable, whereas levels >5 predict that reactions are
likely enough that challenges should be postponed.
The natural history of peanut allergy study suggests
that 20% of a particular population will outgrow
peanut allergy, whereas in a similar population of
children with tree nut allergy the resolution of the
problem was about 5%.33,34 These observations help
in determining and predicting how the immunoassay results should be used. Knight et al.35 have
published a study indicating that a combination of
181

Food Allergy

skin test size and food-specific serum antibody level
to egg white may help clinicians determine the
appropriate time for food challenge.
Other in vitro testing methods that have been
and are under investigation but have not yet been
shown to be clinically useful include the basophil
histamine release assay and the intestinal mast cell
histamine release assay. The basophil histamine
release assay is not actually a new test, having
been used in research applications for decades.36,37
In the past, lymphocyte stimulation tests were
reported to be useful for the identification of subjects with food allergy. These results have not been
reproduced and clinical utility of this approach has
not been demonstrated. However, cellular populations and responses are being investigated using
other hypotheses. Turcanu et al.38 found that in
peanut-allergic individuals T- and B-cell response to
peanut allergens were correlated. A high frequency
of T-regulatory lymphocytes (Tregs) to milk allergy
were reported by Shreffler et al.39 to correlate with
less severe milk-allergic reactions.
There are a number of new and potentially exciting approaches to in vitro testing for both food
and aeroallergen clinical reactivity. The goal is to
improve the diagnostic accuracy, especially the sensitivity, specificity and positive and negative predicative accuracies, of the tests in order to reduce the
need for food challenges, and importantly to predict
when food allergy has resolved.
Component-resolved diagnostic tests are being
developed and preliminary studies have been
reported. The idea is to measure antibody responses
to individual allergen epitopes to establish individual sensitization profiles and specific ‘phenotypes’ of food-allergic individuals. The approach
uses epitopes (pieces of the allergenic proteins) analyzed by microarray technology to predict whether
the subject will or will not react to ingested food.
Which of these epitopes are the most important and
the levels with clinical significance are currently
being determined by research studies. The goal is to
characterize patient heterogeneity and predict clinically significant food allergy (symptomatic sensitization) as opposed to allergen sensitization without
symptoms (asymptomatic sensitization). Thus far,
several important epitopes have been identified for
celery root,40 peanut41 and hazelnut,42 and research
is being directed toward others. Another exciting
result of molecular investigations into antibodies to
food has shown that persistence of food allergy is
more likely if the individual reacts to linear or
182

sequential epitopes rather than conformational
epitopes. Linear epitopes are the primary amino acid
sequence and are not affected by usual cooking pro­
cesses, whereas the conformational epitopes are the
folded structure of the proteins and may be affected
by heating. These findings are now being investigated by microarray techniques as tests to use to
identify individuals whose food allergy has resolved,
but they are not currently available to clinicians.43–53

CLINICAL CASE
A 4-year-old boy has had egg allergy since about age 1.
The original symptoms were hives and vomiting when he
was first fed scrambled egg. About 3 months before the
current visit he had an egg challenge under observation
with hard-boiled egg. At that time his skin test to egg was
4 mm mean wheal diameter and his egg-specific serum
antibody level was 2.2 kU/L. At about 2 g he complained
of abdominal pain and about 15 minutes later he began to
break out in hives, which became generalized. The mother
asked about a challenge with egg baked into something,
as he had recently had a few bites of a muffin with egg in
it and did not have any symptoms. A subsequent
challenge was arranged with well-cooked pancakes, where
the mother made a dozen pancakes containing two eggs.
The child tolerated three pancakes before declaring that
he was full. Over a period of observation of 2 hours no
symptoms were observed. Thus during this period he
tolerated about half an egg well cooked into the pancakes.
The mother was instructed to begin feeding him
approximately half an egg cooked into various baked
goods, and if this was tolerated over a couple of weeks
then to begin slowly and gradually increasing the amount
of egg. Early studies have suggested that this approach
might hasten resolution of the egg allergy (this has also
been observed for milk) in a group of egg-allergic children
who may be reacting to conformation epitopes rather
than linear or sequential epitopes. (It is also probably true
that these children tend to have lower egg- (or milk-)
specific IgE antibody levels, but confirmation of this
hypothesis requires further data.)

Numerous facilities and practitioners have been
using in vitro IgG assays to diagnose food allergy
and ‘food intolerance’ (the latter term having no
specific definition in this context). Some of these
tests have ‘footnotes’ stating specifically that they
are not to be used for diagnosis of IgE-mediated
food allergy. Exactly what they are identifying other
than the individual’s ability to produce IgG antibodies to food protein, which is a normal immune
response, is completely unclear. The absence of any
positive results of IgG to food proteins should raise
an immediate concern of immunodeficiency or
an improperly performed test. Serum food-specific
IgG levels might be elevated in disorders affecting

In Vivo and In Vitro Diagnostic Methods in the Evaluation of Food Allergy

protein absorption in the intestine, such as celiac
disease and perhaps inflammatory bowel disease. At
present these test should not be used in clinical
practice, and the individuals who claim test validity
should validate their results with properly con­
trolled challenge studies. Often these are not covered
by insurance and the cost to patients may be con­
siderable.. The European Academy of Allergy and
Clinical Immunology issued a strong statement to
this effect in 2008,54 and the statement has been
supported by the AAAAI.55 IgG4 (a subclass of IgG) is
likely to give some information about tolerance to
a food rather than a reaction, and may also indicate
that regulatory cells and mediators have been activated.56,57 It is possible that the ratio of IgE to IgG4
(IgE:IgG4) may have clinical utility, but this hypo­
thesis awaits controlled study for confirmation.

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50. Shreffler WG, Lencer DA, Bardina L, et al. IgE and IgG4
epitope mapping by microarray immunoassay reveals
the diversity of immune response to the peanut allergen,
Ara h 2. J Allergy Clin Immunol 2005;116:893–9.
51. Cocco RR, Marvinen KM, Han N, et al. Mutational
analysis of immunoglobulin E-binding epitopes
of beta-casein and beta-lactoglobulin showed a
heterogeneous pattern of critical amino acids between
individual patients and pooled sera. Clin Exptl Allergy
2007;35:831–8.
52. Jarvinen K-M, Beyer K, Vila L, et al. Specificity of
IgE antibodies to sequential epitopes of hen’s egg
ovomucoid as a marker for persistence of egg allergy.
Allergy 2007;62:758–65.
53. Cerecedo I, Zamora J, Shreffler WG, et al. Mapping of
the IgE and IgG4 sequential epitopes of milk allergens
with a peptide microarray-based immunoassay. J
Allergy Clin Immunol 2008;122:589–94.
54. Stapel SO, Asero R, Ballmer-Weber BK, et al. Testing
for IgG4 against foods is not recommended as a
diagnostic tool. EAACI task force report. Allergy
2008;63:793–6.
55. Bock SA. AAAAI support of the EAACI Position Paper
on IgG4. J Allergy Clin Immunology 2010;125:1410.
56. Tomicic S, Norrman G, Flath-Magnusson K, et al. High
levels of IgG4 antibodies to foods during infancy re
associate with tolerance to corresponding foods later in
life. Pediatr Allergy Immunol 2009;20:35–41.
57. Ruiter B, Knol EF, van Neerven RJJ, et al. Maintenance
of tolerance to cow’s milk in atopic individuals is
characterized by high levels of specific immunoglobulin
G4. Clin Exptl Allergy 2007;27:1103–10.

CHAPTER

14 

Oral Food Challenge Procedures
Gideon Lack, George Du Toit and Mary Feeney

KEY CONCEPTS
Oral food challenges (particularly double-blind
placebo-controlled food challenge) represent the
accepted gold standard investigation for objective
diagnosis of both immediate and delayed-onset food
allergy.
 Oral food challenges are clinically indicated to
demonstrate allergy or tolerance to achieve safe dietary
expansion or appropriate allergen avoidance.


The World Allergy Organization (WAO) defines any
adverse reaction to food as food hypersensitivity,
which can be further divided into immunemediated reactions (food allergy) and non-immune
mediated reactions (food intolerance). Foodallergic reactions may be broadly divided into
immunoglobulin E (IgE)-mediated (immediateonset) reactions and non-IgE-mediated (delayedonset) reactions (Table 14.1).
A diagnosis of food hypersensitivity is achieved
using a combination of diagnostic modalities such
as clinical history, physical examination and allergy
testing. When only an equivocal diagnosis is possible, use is made of oral food challenge tests. The
oral food challenge (especially double-blind
placebo-controlled food challenge – DBPCFC) represents the gold standard investigation for the diagnosis of both immediate and delayed food-induced
allergic reactions.1,2
© 2012, Elsevier Inc

A particular challenge design is selected according to
clinical history, age of patient and associated factors at
the time of the index reaction.
 Using standardized procedures, safe and objective
challenge outcomes can be achieved.


Rationale
Oral food challenges are diagnostic tests which aim
to achieve safe dietary expansion or appropriate
allergen avoidance; to achieve this, the oral food
challenge hopes to demonstrate an unequivocal
outcome of either ‘tolerance’ or ‘allergy’. The outcomes may include symptoms and signs that indicate IgE-mediated or non-IgE-mediated reactions.

Indications for an oral
food challenge
The indications for undertaking an oral food challenge are varied but fall broadly into two categories,
those where a state of either allergy or tolerance to
a food is anticipated but uncertain. The rationale
for these is described in Table 14.2.

Food Allergy
Table 14.1  Classification of food hypersensitive reactions

IgE-mediated, immediate-onset symptoms and signs
Gastrointestinal

Gastrointestinal anaphylaxis: symptoms include vomiting, pain and/or diarrhea

Cutaneous

Urticaria, angioedema, pruritus, morbilliform rashes and flushing

Respiratory

Acute rhinoconjunctivitis, wheezing, coughing and stridor

Generalized

Anaphylaxis

Mixed IgE- and cell-mediated, immediate–delayed onset symptoms and signs
Gastrointestinal

Eosinophilic esophagitis

Cutaneous

Atopic eczema

Cell-mediated, immediate–delayed onset symptoms and signs
Gastrointestinal

Food protein-induced enterocolitis, food protein-induced proctocolitis and food protein-induced
enteropathy syndrome – which may present with a clinical picture of ‘sepsis’

Respiratory

Food-induced pulmonary hemosiderosis (Heiner syndrome) (rare) – pulmonary hemosiderosis or
bleeding in the lower respiratory tract.

Mechanism uncertain, immediate–delayed onset symptoms and signs
GI dysmotility

Gastroesophageal reflux*
Constipation*
Infantile colic*

*Associations remain controversial.

Table 14.2  Indications for performing a food challenge

Indication

Rationale

Demonstrate tolerance

1.  Allergy suspected to have been outgrown, e.g. the child who was previously egg
allergic but now returns ever-decreasing allergy test results.
2.  When the food has been tolerated in some presentations but not others e.g. baked
egg in cakes tolerated but scrambled egg causes a reaction.
3.  When allergy tests suggest tolerance, but food never eaten and patient and/or
parent too cautious to introduce at home.
4.  Cross-reactivity suspected, e.g. the child with a low positive IgE result to wheat but
high positive grass pollen sensitization.
5.  When the diet is restricted due to a suspicion that one or more foods is resulting in
delayed allergic symptoms, e.g. eczema, gastroesophageal reflux.
6.  To establish a tolerance threshold to allergen proteins (currently restricted to the
research setting).
7.  When multiple dietary restrictions are maintained but symptoms are subjective.

Demonstrate allergy

1.  Suspected food allergic reaction but cause uncertain despite SPT and Sp-IgE testing,
e.g. composite meal eaten.
2.  Suspected food allergic reaction but equivocal or inconsistent symptoms following
consumption of a particular food.

Monitor therapy for food allergy

To monitor response to immunomodulatory treatment in the research setting.

It has been proposed that the clinician should
aim to achieve a 50% positive to negative outcome
ratio when performing oral food challenges (OFCs)
in adults and children with established allergies.3
This outcome indicates that the patients who are
selected for challenges are those with the highest
186

risk to benefit ratio of having a negative challenge.
OFCs are not without risk and may induce severe,
occasionally life-threatening reactions or more
commonly less severe symptoms such as an exacerbation of atopic dermatitis. They are also labour
and resource intensive. For these reasons, to

Oral Food Challenge Procedures

minimize the need for oral food challenges, use is
made of established diagnostic modalities, of which
the clinical history is the most helpful. There are,
however, scenarios where the history is of limited
use, such as when a food has never been eaten. The
clinical history is also dependent on the disease in
question and the suspected allergenic trigger. For
example, hives and angioedema that develop soon
after peanut ingestion make for a very likely diagnosis of peanut allergy,4 but abdominal pain that
develops 4 hours after eating wheat makes for a less
certain diagnosis of IgE-mediated wheat allergy.
If the history results in an equivocal diagnosis use
is then made of validated allergy tests (such as the
skin prick test and/or specific IgE determination)
to help attain a post-test probability of allergy or
tolerance. To facilitate this process (at least for
immediate-onset allergies), where possible, positive and negative predictive values (PPV, NPV) have
been determined; such values are available for the
diagnosis (with 90% or 95% certainty) of egg, cows’
milk, peanut and fish allergy (Table 14.3).5–7 Values
could not be established for other common food

Table 14.3  Positive predictive values for food-specific
IgE and skin prick tests*

≥ 95% Specific IgE levels (KU/L) positive predictive Values
Egg
  Infants ≤ 2 yrs
Milk
  Infants ≤ 2 yrs

7
2
15
5

Peanut

15

Tree nuts

15

Fish

20

≥ 95% skin prick tests (wheal diameter in
mm) positive predictive values
Milk

8

  Infants ≤ 2 yrs

6

Egg

7

  Infants ≤ 2 yrs

5

Peanut

8

  Infants ≤ 2 yrs

4

*Negative allergy tests (specific IgE levels (<0.3 kU/L) and/or skin prick
tests) may still be associated with clinical reactions. Allergy tests
should therefore never be interpreted in the absence of a thorough
allergy history.38

14

allergens such as soy and wheat. The use of allergy
test predictive values significantly reduces the need
for diagnostic dietary investigations if immediateonset allergies are under investigation, but are not
of use for the diagnosis of delayed-onset food
induced hypersensitivity. Predictive diagnostic
values are significantly influenced by numerous
variables, such as the age of the patient and atopic
phenotype, e.g. the presence of eczema. The values
are therefore most accurate if validated for the specific population served. Another way to overcome
this problem is the use of likelihood ratios (LRs).
The LR for a test result is the likelihood that a positive test would be expected in a patient with the
food allergy compared to the likelihood that the
same result would be expected in a patient without
food allergy. LRs have been established for selected
foods in different centers.9 The advantage of this
approach is that LR values are independent of the
prevalence of the condition tested. LRs can therefore be used to calculate the likelihood of a disease
both within a tertiary care center and in the primary
care setting. Before a patient’s test result can be
interpreted using the LR, their pre-test probability
must be estimated. This is the chance that they are
food allergic based only on their clinical presentation and risk factors prior to any test result. The
post-test probability of food allergy for a subject
can be derived from a statistically derived nomogram (Fig. 14.1). This takes into account the subject’s pre-test probability and the LR corresponding
to the test result. The use of these values combined
with the medical history leads to an accurate diagnosis of food allergy in 70% of patients.8
Despite the use of the above testing methodologies, oral food challenges are often required in
order to obtain a certain diagnosis of allergy or
tolerance.

Oral food challenges: design and
methodology
The design and methodology by which oral food
challenges can be performed varies enormously and
is influenced by the indication for which the challenge is being performed.2,10,11 It is, however, important to remember that in essence a supervised food
challenge entails no more than safely exposing the
patient to doses of a food allergen and, if initially
tolerated, the patient continuing to eat the food
over sequential days. Challenges can be performed
187

Food Allergy
SPT (mm)

0 –2

3–7

>8

LR (mm)

0.2

1.8



Open vs blinded challenges
99 Allergenic

0.1
0.2
0.5
1

95
SPT 8 mm

2
5

SPT 3 mm

10
20
30
40
50
60
70
80
90

SPT 0 mm

1000
500
200
100
50
20
10
5
2
1

90

.50
.20
.10
.05
.02
.01
.005
.002
.001

95

80
70
60
50
40
30
20
10 Needs
challenge
5
2
1

Tolerant

0.5
0.2

99
Pre-test
probability

LR

0.1
Post test
probability

Figure 14.1  Using likelihood ratios to diagnose egg
allergy. Consider a 3-year-old child who has never eaten eggs
and is not atopic. Pre-test probability is estimated at 2.5%
(prevalence in childhood). The LR is chosen according to SPT
result. A SPT of 8 mm has a high LR and the post-test probability
for egg allergy is >99%: this child is therefore considered allergic.
An SPT of 3 mm has a medium LR and the child has a post-test
probability of 10% allergy to egg. Diagnosis is in doubt and a
DBPCFC is required. An SPT of 0 mm yields a post-test
probability of <1%: this child is therefore deemed to be tolerant.
With permission from Lack G. Clinical practice. Food allergy. N
Engl J Med. 2008; 359(12): 1252–60.

diagnostically in the context of both suspected
immediate IgE-mediated symptoms and delayed
non-IgE-mediated symptoms. These challenges are
broadly similar in both scenarios but with a few
important differences (considerations specific to
food challenges for non-IgE mediated symptoms
are detailed in the section ‘Oral Food Challenges
for the assessment of non-IgE-mediated food
(delayed) hypersensitivity’). A particular challenge
design is selected according to clinical history, age
of the patient and associated factors at the time of
the index reaction. The variables and associated
considerations that refine the choice of a particular
design are described in Table 14.4.
188

An open challenge mimics ‘real-life’ exposure to the
food, albeit in a supervised setting. The patient is
fed an age-appropriate (Table 14.5, Table 14.6)
quantity of the challenge food in an open – i.e.
unmasked and unblinded – manner. Depending on
the risk profile, this can be performed in a single
meal or in increments (incremental oral food challenge). Open oral food challenges are associated
with a high degree of bias as both the patient and
the observer (clinician) know what is contained in
the challenge. However, the advantages of open
challenges are that they are simple to carry out and
reproduce ‘real-life’ exposure to a food in terms of
the form, quantity and method of exposure. An
open oral food challenge carries a high negative
predictive value, i.e. when negative it is highly likely
that the patient is truly tolerant of that food.12 It is
also useful if an unequivocal positive outcome
(where both subjective and objective symptoms
and signs are noted) is achieved. Open challenges
that result in ‘atypical’ or ‘subjective’ symptoms
only are less helpful, and always need to be followed by a blinded challenge; one study reports
that oral food challenges produced 27% more positive challenges than DBPCFC in a group of children
aged 1–15 years.13 Subjective symptoms are reported
less frequently in infants and young children ≤ 3
years, and open oral food challenges are recommended in this group; they can also be useful for
preliminary screening for food allergy.14
Blinded challenges can be single- or doubleblinded. Ideally, a food should be blinded for taste,
smell, texture and appearance (consistency, color
and shape). The placebo and the active (allergencontaining) food should be indistinguishable from
each other, i.e. either the active food must be altered
to resemble the placebo in all aspects, or vice versa.
A single-blind challenge involves masking the
challenge food so that only the patient, and for
younger children their family and/or carer, is
unaware of what they are eating. A placebo food
may also be included in the design. The staff performing the challenge are not blinded. Single
blinding reduces – but does not eliminate – bias in
terms of subjective symptoms reported by the
patient, but does not control for any influence of
observer bias by parents or staff.
A DBPCFC is achieved when the blinding process
is extended to include the patient, family/carers
and staff. Although DBPCFCs are considered the

Strictly avoid use of allergenic ingredients for individual patient
Minimize number of ingredients used
Provide adequate allergen protein in a manageable portion size (see Table 14.6)
For placebo foods sensory qualities should closely replicate those of active challenge food

Choice of food matrix

There are many indications for performing an oral food challenge; these are listed in Table 14.2
One or more of these factors have been shown to affect the severity of allergic reactions

The age of the patient will affect the type of food, food volumes and number of feeds. Younger children may require less
stringent blinding of foods than older children and adults

Indication for food challenge

Clinical history at last known reaction
Immediate or delayed symptoms
Severity of symptoms
Association with other conditions, e.g. asthma

Age

Patient-related variables

Interpretation of challenge outcome

Challenge outcomes may be immediately apparent, i.e. within an hour of ingestion when due to IgE-mediated immune
mechanisms. Delayed food-induced hypersensitivity reactions may arise over hours or even days (see Table 14.10)

This choice depends on the risk associated and capacity to identify and treat anaphylactic reactions. Logistical dietetic factors
are also important, e.g. DBPCFCs will be difficult to achieve in the home environment
Low-risk challenge, cooperative patient
High-risk challenge e.g. FPIES
Low-risk challenge, delayed symptoms

Location

•  Day admission
•  Admission to hospital ward
•  Home

•  If a negative outcome is anticipated and there are no safety concerns, a single dose is appropriate. If not, incremental doses
increase safety due to gradual increases in exposure to food allergen
•  Low doses used for threshold studies in research setting or for patients at high risk of a severe reaction, higher initial doses
are more practical in the clinical setting
•  Equivalent to an ‘age-appropriate’ portion, preferably a large portion, of the food (see Table 14.6)
•  At least 15 minutes for immediate symptoms or 24–48 hours for delayed symptoms. Adjust intervals depending on patient
history
•  Between 2 hours (immediate symptoms) and 1–4 weeks (delayed symptoms)


•  Initial dose
•  Top dose
•  Time intervals between doses
•  Total duration of challenge

Doses
  Number of doses

The challenge food should closely replicate the usual edible form of the food or form of the food implicated in allergic reaction.
Food processing, and the food matrix can significantly influence allergenicity of the food, e.g. baked vs raw egg. For oral food
challenges performed to diagnose the pollen–food syndrome, fresh fruit and vegetables should be used as the responsible
proteins are commonly heat labile

Design selected according to the indication and purpose for which the challenge is being performed (see section ‘Open vs
Blinded Challenges’)

Form of challenge food




Design
  Open (single dose or incremental)
  Blinded (single or double)

Challenge-related variables

Table 14.4  Variables associated with oral food challenges

Oral Food Challenge Procedures

14

189

Food Allergy
Table 14.5  Foods commonly used to disguise allergens
for food challenges (other food allergens depending)
Cows’ milk

Amino acid formula, extensively
hydrolyzed formula, soy formula

Soy milk

Amino acid formula, extensively
hydrolyzed formula, cows’ milk

Egg

Blended in yogurt, ingredient in
cakes or biscuits, mashed potato

Peanut

Strongly flavored biscuits or cakes,
chocolate pudding, fruit smoothie

Wheat

Substitute gluten-free, wheat-free
products, e.g. pasta, biscuits,
oatcakes

Sesame

Hummus, chocolate pudding, soy
dessert, lentil soup, beefburger

Shellfish

Beefburger, strongly flavored sauces

Meat

Alternative meat-based burger

Colorings or
preservatives

Fruit juice, vegetable juice

Fruit or
vegetables

Mix with alternative strong tasting
fruit/vegetable

gold standard diagnostic modality5 they require
additional facilities and a skilled medical, nursing
and dietetic team. In particular, dietitians are
needed to develop, prepare and store blinded
recipes, and need to be able to reproduce a dose if
necessary. During the blinding procedure neither
the patient nor the observers know which is the
active food and which is the placebo (these are
prepared by a third party, usually a skilled dietitian). The order of doses (active or placebo) is
random and not revealed until after the challenge
is completed; in the event of a negative outcome,
‘unblinding’ only occurs after all doses are consumed and the observation window is past, but in
the event of a positive reaction unblinding occurs
sooner. In the event of equivocal symptoms during
the DBPCFC, the last dose should be repeated
(only the dietitian who prepared the foods will be
aware if this dose is active or placebo). This rigorous procedure prevents reporting bias by both
parties. In order to openly prove tolerance to the
patient, all negative DBPCFCs should be followed
by an open feeding of age-appropriate portion of
the food in its natural or ‘real life’ form.20
Owing to the practical difficulties associated
with the DBPCFC, use thereof is generally limited
to specific diagnostic scenarios such as clinical
190

research, diagnosing chronic symptoms or subjective complaints, e.g. migraine, chronic fatigue syndrome.5,21 In the clinical setting a DBPCFC is used
only where there are atypical or unverifiable subjective symptoms or high levels of anxiety on the part
of the patient (and/or parent).
Although efforts have been made to standardize
OFCs there remains a lack of agreement in terms of
the type and quantity of the food allergen to be
administered, the timings between doses, observation periods and blinded recipes used.2,11,15–17

Form of challenge food
The common food allergens have variable sources
and characteristics. Although the proportions of
carbohydrate, protein and fat vary, most allergens
are found in foods with a high protein content. The
majority of food-induced allergic reactions arise as
a result of reactions to the food proteins.18
The challenge food should closely resemble the
usual edible form of that food and ideally mimic
the food implicated in the history, as this most
closely replicates the ‘real-life’ setting. This is particularly important for open challenges, and for the
open dose given after a DBPCFC, to confirm tolerance. Careful consideration of the clinical history is
essential when choosing the form of a challenge
food, as processing may influence the allergenicity
of a food. The effects of food processing may be
allergen specific. For example, the allergenicity of
egg and milk is reduced by heat processing, whereas
that of peanut is increased by roasting.19,20
Other forms of challenge food, e.g. dried foods
such as powdered egg or peanut flour, are commonly used for DBPCFC for convenience of storage,
greater ease of blinding, or because of requirements
for a high concentration of an allergen in a small
volume, e.g. 4 g peanut protein can be provided in
8 g of peanut flour (50% peanut protein) compared
to 16 g of peanut butter (25% peanut protein). This
helps reduce the portion sizes required to deliver
an adequate amount of allergen during the challenge. Large amounts of foods may cause symptoms
such as nausea or vomiting, which could be falsely
interpreted as an allergic reaction to either the challenge food or the placebo used.
It is essential to consider issues of food safety
when deciding who will provide the challenge
food, e.g. hospital catering service or parent. Where
a catering service provides the food, the staff
setting up the challenge must ensure that they have

Oral Food Challenge Procedures

14

Table 14.6  Challenge doses for common food allergens

EAACCI-proposed initial doses

Total cumulative dose for open food challenges

Allergen

Dosing increments

Age appropriate
portion sizes*

Initial Dose

Peanut

0.1 mg

0.1 g, 0.25 g, 0.5 g, 1 g, 2 g,
4 g, 8 g, 20 g

1–2 tablespoons (15–30 g)
peanut butter

Milk

0.1 mL

0.5 mL, 1 mL, 2 mL, 5 mL,
10 mL, 20 mL, 40 mL,
100 mL, 180–240 mL

180–240 mL (6–8 oz) milk or
infant formula
1 −1 cup yogurt
2
1 −1 cup cottage cheese
2
15–30g ( 12−1 oz) hard cheese

Egg

1 mg

1 g, 2 g, 5 g, 10 g, 20 g,
60 g

1 hard-boiled or scrambled
egg (60 g)
1 slice of French toast
(1 egg per slice of bread)

Cod

5 mg

1 g, 2 g, 5 g, 10 g, 15 g,
30 g, 60 g

60–90g (2–3 oz) cooked fish

100 mg

1 g, 2 g, 5 g, 10 g, 25 g,
80 g
1 g, 3 g, 6 g, 20 g

1 −1 cup cooked pasta
2
15–30g ( 12−1 oz) wheat-based
cereal
1 −1 slice bread
2
1 −1 muffin or bread roll
2

Wheat

Soy

1 mg

0.5 mL, 1 mL, 2 mL, 5 mL,
10 mL, 20 mL, 40 mL,
100 mL

1
2
1
2

Shrimp

5 mg

0.5 g, 1 g, 4 g, 15 g, 60 g

60–90g (2–3 oz) shellfish

Hazelnut

0.1 g

0.25 g, 0.5 g, 2 g, 4 g, 15 g,
30 g

30–40 g crushed tree nuts or
25–30 pieces

−1 cup soy beverage
−1 cup tofu

*For older teenagers and adults larger portion sizes should be used. Adapted from Work Group report: oral food allergy challenge testing.2

up-to-date food safety standards and procedures in
place to minimize the risk of cross-contamination.
Where food is to be brought from home the
patient must be informed of how to source uncontaminated and safe food products – e.g. if raw
eggs are to be used these should be confirmed
salmonella-free, – as well as how to best process
the foods to optimize the food matrix for the
challenge (see below).

Choice of food vehicle
Masking of a challenge food in a vehicle i.e. with
other ingredients is sometimes required in open
challenges to make the food more palatable to the
patient. In DBPCFC, the use of a vehicle is always
required to disguise the allergen and to ensure
that the placebo food closely replicates the sensory

qualities of the active challenge food, including
taste, smell, texture and appearance (consistency,
color, shape).
In both instances the vehicle should avoid using
allergenic ingredients. Minimizing the number of
ingredients used will help avoid unknown side
effects of other ingredients. A food matrix effect has
been described in some preparations of challenge
foods which arises as a result of the interaction
between fat, carbohydrate and proteins; this may
affect the allergenic characteristics of the food as
well as allergen absorption and processing through
the GI tract:21,22 e.g. a higher fat recipe resulted in
delayed reactions at higher doses during a peanut
challenge. These characteristics need to be considered when developing these recipes.
Capsules have been used as a convenient way to
disguise active and placebo foods, but safety can be
191

Food Allergy

significantly compromised. There is a greater chance
of a severe reaction as the first immune presentation and recognition of the allergen will be in the
gut at time of digestion of the full capsule dose,
after having bypassed the normal physiological
route of allergen detection, i.e. the oropharynx.

Challenge foods for DBPCFC
The challenge foods used for DBPCFC need to
contain enough of the allergen to elicit allergic
reactions and it is important that no perceivable
differences between the placebo and the active
food. Developing validated recipes is difficult and
time-consuming and the processes for doing so
have not been standardized. Until recently, available validated recipes contained amounts of allergens that were too low for many food challenge
procedures. To fully validate challenge foods for
clinical use, statistical modeling that incorporates
advanced sensory discrimination testing, such as
paired comparison, directional difference or triangle testing, is required.23 These tests are used to
determine whether a specified or unspecified difference exists between active and placebo foods.
In the case of validating foods for DBPCFC, active
and placebo food samples are coded and tasted
under controlled conditions in a specified order.
Assessors may be asked to describe observed differences, such as taste, and estimate how large they
are between samples (paired comparison or directional difference tests); or, in the case of triangle
testing, they simply indicate whether they can identify which is the ‘odd’ sample, e.g. the one that
contains peanut when presented with three samples
(two active and one placebo, or one active and
two placebo). Comparing the number of correct
responses obtained with standardized tables helps
to determine whether a perceivable difference
between samples has been shown to exist. Ideally,
use should be made of a large number of panelists
in order to minimize bias and to optimize statistical power.23
Most studies to date have used adult tasting
panels for sensory testing. Untrained or age-specific
assessors i.e. groups more similar to those who
would actually be receiving the challenge foods,
could be used, and would likely show less stringent
blinding to be adequate, particularly in young children; that is to say larger amounts of allergen could
be blinded in a volume the child could manage.
However, the power of sensory testing is generally
192

poor and hundreds of assessors would be required
to achieve adequate powering.24
By optimizing the conditions of sensory testing
i.e. using trained tasting panels, fewer assessors are
required. Recipes validated for blinding of cow’s
milk, egg, peanut, hazelnut and cashew suitable for
children greater than 4 years old and adults (some
also suitable for younger children) have been published.23 These recipes mask a total amount of allergenic ingredient equivalent to one food serving
disguised in 250 ml liquid or 125 g solid food.
Validated recipes for soy and wheat are available
which have managed to disguise smaller amounts
of these allergens.27
Utility of active challenge foods also needs to be
proven with respect to the ability of the food to
induce an allergic reaction and the likely dose
responses at which this is likely to occur in allergic
individuals. It is not surprising, therefore, that few
validated DBPCFC recipes exist.
Familiar foods are recommended as the starting
point when developing DBPCFC recipes, as they
tend to be more acceptable; however, it is important
to remember that adults and children who have
been on exclusion diets for many years may be
reluctant to eat the challenge foods. Having been
advised, sometimes for many years, to avoid a food;
particularly one which has caused previous allergic
reactions, they may have become averse to eating it.
Alternatively, the type of food they are being asked
to eat may be unfamiliar to them e.g. children who
have been following egg-free diets from infancy
often do not consider cakes to be ‘treats’ in the way
that other children do as they are not familiar with
them. In these situations, ‘creative dietetics’ may be
required to disguise the food so that it does not
look or taste like the food they have been avoiding
e.g. disguising eggs in French toast or nuts in a
flapjack. See table 14.5 for foods commonly used
to disguise food allergens for challenges. A choice
of more than one challenge food may also be necessary to deal with fussy eating which is relatively
common among children with food allergies.
Allergenic ingredients are commonly substituted
in active and placebo recipes with ‘free from’ alternatives which may behave quite differently from
typical ingredients, affecting not only the taste of
the food but other qualities such as texture and
color, or even cooking time. It is therefore necessary
to have a dietitian who is both creative and has a
good knowledge of the use of these alternative
ingredients when preparing these recipes.

Oral Food Challenge Procedures

Placebos
The use of placebos in allergy testing is usually
restricted to older patients (adolescents and adults),
research settings or after open challenges have
resulted in atypical or non-specific symptoms. Their
inclusion helps to increase the validity of the challenge outcome by minimizing false positive results.27
The disadvantages of placebo use include the additional doses required for the challenge. A greater
number of doses take longer to consume and may
frustrate younger children; in addition, the greater
total volumes required to be eaten may fill the
young child before the challenge is completed.
There is also a chance that the patient may be allergic to the placebo used (if different ingredients from
those in the active challenge food are used).
For patients who had initially presented with
objective allergic signs it may be that a single
placebo dose (often given first) is sufficiently robust
in providing a valid outcome; this is due to the low
frequency of placebo reactions in such patients. For
those with more subjective symptoms, it is recommended that placebo-controlled oral food
challenges be delivered on two separate occasions.
This may involve two sessions on the same day
(one with active food, the other with placebo,
separated by at least 2 hours) or indeed over 2 days
(one day being for the administration of placebo
and the other for the active food. The open dose
only follows the second day’s feeds).25 Combining
the two sessions by interspersing placebo doses
with active doses is more practical where a prolonged challenge procedure is not feasible, e.g.
using three active and three placebo or three active
and two placebo doses.2,16
Where reported symptoms are delayed in onset,
active and placebo doses should be administered
on separate days, in a random order, separated by
days or sometimes weeks.
Both objective and subjective placebo events have
been reported; these are usually immediate, i.e.
within 20 minutes.27 Where placebo doses are given
interspersed with active doses, it cannot always be
certain when a reaction takes place after the administration of a placebo dose (unless it also occurs
after an additional placebo dose), whether this is
due to the placebo dose or whether it is a delayed
reaction to one of the preceding active doses. It is
therefore important to always confirm an allergy to
the placebo by repeating an oral food challenge to
the same placebo but in the absence of the

14

challenge food. Reported rates of placebo reactions
are 7% in threshold studies.29,30 There are studies
which report no placebo-induced reactions; this
may be due to short observation periods following
the administration of placebo and the active food.
An interval of at least 15 minutes between doses
should therefore be observed. Frequency of placebo
events must not be excluded from statistical analysis, as this risks overestimating the frequency of
patients having actual allergies.5,15

Doses
The key considerations when choosing doses for
oral food challenges are the choice of initial or
starting dose, incremental doses and the top dose.
These should be individualized to the person(s)
undergoing the challenge, thereby maximizing the
reliability of the outcome and minimizing the risk
of a severe reaction.
The European Academy of Allergy and Clinical
Immunology (EAACI)’s proposed initial doses for
common food allergens5 (Table 14.6) are useful for
threshold studies (which investigate the lowest
dose of an allergen capable of eliciting an allergic
reaction) or where the patient is considered at risk
of a severe reaction, as very low starting doses are
used. However, for most patients higher initial
doses may be used which are more practical to
measure and avoid food challenges being unnecessarily long (see Table 14.6). An appropriate initial
dose is one smaller than the patient is known to
react to.29
Many studies describing food challenge procedures state that tolerance is demonstrated if a total
cumulative challenge dose of 8–10 g dry weight, or
60–100 mL or g ‘wet weight’ in children,15 or 15 g
dry weight in adults is tolerated.2 However, these
are reported with limited details of the conversion
factor from dried to wet foods, and the exact nature
(e.g. food matrix) of the food. Some more recent
studies quantify amounts of challenge materials as
an amount of allergen protein.2,26 Additionally, as
all negative DBPCFCs should be followed by an
open food challenge using an age-appropriate
portion of the food, the total cumulative dose in
these challenges is typically twice that of open challenges. In younger children it may only be possible
to achieve a lower top dose, e.g. an adolescent challenged to peanut may manage a top dose of 5 g
peanut protein (equivalent to a generous spreading
of peanut butter on bread), whereas a child younger
193

Food Allergy

than 5 years may only manage a top dose of 2 g
(equivalent to a rounded teaspoon of peanut
butter). The use of excess incremental feeds may
upset the child or induce non-specific gastrointestinal symptoms, e.g. vomiting, which may then prove
difficult to exclude as an allergic feature.
Although there is some knowledge about objective and subjective symptoms at low doses, less is
known about the role of high doses in inducing
symptoms. There is much debate as to the lowest
starting doses for food challenges, but no data to
tell us where an oral food challenge should stop.
For example, a child may pass an oral food challenge giving 4 g allergen protein and be said to be
tolerant, but could react at a threshold of 6 g. This
phenomenon is best described as ‘dose-dependent
tolerance.’ One audit of food challenge procedures
showed that 10% of children only reacted at the top
4 g peanut protein dose (total cumulative dose
7.9 g peanut protein)30 and a second study using
DBPCFCs demonstrates that 4% of children reacted
only after the open challenge dose;31 this raises the
possibility that there may be additional children
who could pass a challenge ending with a 4 g or
even 5 g top dose, but would react if higher doses
were given. It is important, therefore, that challenges are finished with a generous ‘age-appropriate
portion’ dose, i.e. the total cumulative challenge
dose will then be higher than the patient would
typically be expected to manage in daily life.
Further research is required to define an upper
NOAEL (no observed adverse effect level) or top
challenge dose to which no one reacts. Only tolerant
patients will progress to this dose in a challenge,
allergic patients will have reacted at a lower dose.
This is particularly relevant in oral tolerance induction studies (specific oral tolerance induction), as
research indicates that some participants in these
studies react at doses that would not be tested in the
typical clinical setting, e.g. a study investigating oral
tolerance induction to milk in a group of milkallergic children describes that during the maintenance phase of the study a number of patients
reacted to 16 g milk protein (equivalent to 440 mL
milk), which is higher than doses typically used in
oral food challenges.32

Number of doses and interval
between doses
The number of doses, and intervals between doses,
should match the anticipated safety and outcome
194

of the challenge. For example, a single-dose open
challenge can be used when a negative outcome is
anticipated and no safety concerns exist. Examples
would include baseline challenges at the point of
entry into research studies in participants with
negative allergy tests and no history of reactivity to
that food. An additional example would be when
tests are negative but the participant and/or family
are reluctant to introduce the food in an unsupervised setting. Use of a single-dose feed serves to
minimize the time and resources required for the
challenge.
Incremental challenges allow for more gradual
exposures to the food, hence increasing safety.
There is a lack of consensus as to how these doses
should be increased, with some studies recommending doubling doses.2,15,16 Other studies advise
using a logarithmic mean, i.e. 1, 3, 10, 30, 100
until the top dose is reached. The choice of increment will depend on the anticipated risk. Many
studies demonstrate that positive challenge symptoms (both objective and subjective) typically
occur at the lower doses; this may also be true for
symptom severity, i.e. more severe symptoms
occurring at lower doses.33 This justifies smaller
increases in doses in the early stages of an incremental challenge. The downside of oral food challenges that make use of excessive dose protocols
is that young children easily become fatigued
(remembering that placebos may need to be
included in the regimens). There may also be time
implications, e.g. the use of four active doses and
three placebo doses, with at least 15-minute observation intervals and an hour’s observation post
challenge, will result in a challenge duration of
195 minutes (if feeds are all eaten on time). If cannulation is required beforehand, additional time
will be required for the procedure (and the use of
local anesthetic creams).
Advised time intervals between doses also vary,
e.g. 10–60 minutes or 15–30 minutes. The most
appropriate choice depends on safety and feasibility. The use of an interval that is too short may
compromise safety by not allowing enough time for
an allergic reaction to present. A short interval may
also complicate the interpretation of a reaction
which occurs after a placebo dose, i.e. is it the
placebo or the preceding dose of the food allergen
that caused the reaction? We make use of an interval of ‘at least 15 minutes’, which reduces the above
complications and minimizes the overall duration
of the oral food challenge.

Oral Food Challenge Procedures

Site of application of first dose
There is not always absolute concordance between
allergic symptoms that occur upon skin contact and
symptoms upon ingestion. For this reason it is
unwise to first apply the food to skin, particularly
eczematous skin, prior to commencing the oral
challenge. Most challenges do, however, commence
with application of the food to the mucosa of the
lips (which represent the start of the gastrointestinal tract and which are densely populated with
allergen recognition cells).

Logistics
The oral food challenge should be considered a
formal invasive medical investigation. For this
reason, signed informed consent – and, when

14

appropriate, patient assent – is mandatory prior to
the commencement of an oral food challenge.
Patients and their families should be reminded
beforehand about the need to stop taking those
medications that are contraindicated at time of challenge. Patients should always be thoroughly examined prior to the commencement of the challenge to
assess for general well-being and, in particular, the
presence of pre-existing rashes and/or wheezing.
Failure to do so may result in difficulty in interpreting equivocal symptoms and signs during the challenge. As it is not uncommon for children who are
closely observed for 6–12 hours to develop nonspecific ‘blotches’, pre-existing rashes should be
noted in detail. It should be checked that the patient
has stopped all medication, such as antihistamines,
that might mask allergic reactions when they occur
(Table 14.7). Patients should omit medications that

Table 14.7  Guidelines for discontinuation of medications that might interfere with interpretation of oral food
challenges With permission from Nowak-Wegrzyn A, Assa’ad AH, Bahna SL, Bock SA, Sicherer SH, Teuber SS. Work Group report:
oral food challenge testing. J Allergy Clin Immunol. 2009; 123(6 Suppl): S365-83.

Medication†

Last dose before oral
food challenge

Medication†

Last dose before oral
food challenge

Oral antihistamines

3–10 d

Inhaled cromolyn sodium

48 h

Cetirizine

5–7 d

Nedocromil sodium

12 h

Diphenhydramine

3 d

Theophylline (liquid)

24 h

Fexofenadine

3 d

Theophylline long-acting

48 h

Hydroxyzine

7–10 d

Ipatropium bromide
(inhaled/intranasal)

4–12 h depending on
formulation and dosing
interval

Loratadine

7 d

Antihistamine nose spray

12 h

Oral H2 receptor antagonist

12 h

Antidepressants

3 d–3 wk, drug-dependent
and dose-dependent

Oral/intramuscular/
intravenous steroids‡

3 d–2 wk

Leukotriene antagonist

24 h

Short-acting bronchodilator
(albuterol, metaproterenol,
terbutaline, isoproterenol)

8 h
24 h

Long-acting bronchodilator
(salmeterol, formoterol)

8 h

Oral/intranasal α-adrenergic
agents
Oral β-agonist

12 h

Oral long-acting β2-agonist

24 h

Drugs that may be continued
Antihistamine eye drops
Inhaled/intranasal
corticosteroids
Topical steroids
Topical immunosuppressive
preparations: pimecrolimus,
tacrolimus

†Aspirin and other non-steroidal anti-inflammatory agents and angiotensin-converting enzyme inhibitors should be avoided because of their
theoretical ability to enhance or induce allergic reactions and potential interference with an oral food challenge outcome interpretation.
‡This suggested guideline is based on concerns regarding the potential for suppression of the late-phase responses. In addition, the patient who
received a short course of systemic corticosteroid may be going through an exacerbation that would either interfere with the oral food challenge
interpretation or potentially worsen the severity of a reaction. In patients who receive chronic therapy with systemic steroids, such as for
inflammatory/rheumatologic diseases, the risk–benefit ratio for stopping steroid therapy and substituting an alternative therapeutic agent vs
performing an oral food challenge while the patient remains on steroid should be evaluated on an individual basis.

195

Food Allergy

may interfere with the treatment of severe allergic
reactions with adrenaline, e.g. β-blockers. See Table
14.7 for further details.

challenges are not reported. Table 14.9 details both
absolute and partial contraindications to an oral
food challenge.

Safety and contraindications

Determination of oral food
challenge outcome

34

Food challenges are not without risk. To optimize
safety, procedures should be in place to deal with
allergic reactions and staff should be trained in
the recognition and emergency management
thereof. Age- and weight-appropriate emergency
medications that may be required should be written
up on medication charts prior to commencing the
challenge.35,36 A careful assessment of patients prior
to performing the challenge, including assessment
of lung function (in older children), is mandatory.
Pre-existing airway inflammation, e.g. infection or
asthma, is a major risk factor for severe anaphylaxis
and should be excluded. Patients who are at
increased risk of experiencing a severe reaction
(Table 14.8) should ideally be cannulated prior to
commencing a challenge37, although cannulation
was not performed or required in a study where
peanut challenges were performed in children with
positive peanut allergy tests and a management
plan should be in place in the event of a severe reaction, i.e. resuscitation response teams should know
that an ‘increased risk’ challenge is taking place and
the location of the challenge; ICU staff may also
need to be notified. Nonetheless, oral food challenges have an excellent safety record if patients are
carefully assessed before an oral food challenge that
is then performed by experienced staff in a safe
environment. Indeed, fatalities due to oral food

Although oral food challenges usually result in
an unequivocal outcome, indeterminate scenarios
are not uncommon. Although numerous scoring
systems have been devised for the evaluation of
immediate-onset IgE-mediated allergic reactions,
this is not the case for all of the non-IgE-mediated
(delayed-onset) food hypersensitivities.

Scoring of immediate-onset IgE-mediated
allergic reactions
Oral food challenge outcome assessments are
easiest to make at the extremes of clinical
presentation, i.e. the child who happily eats an ageappropriate portion of a food allergen in an open
challenge is tolerant, as false negatives are extremely
rare; likewise, the child who develops immediateonset allergic symptoms and signs during a DBPCFC
is allergic to that food. However, if the investigator’s
instinct is that the allergen is an unlikely trigger,
then an allergy to the placebo, or accidental contamination of the food with a different food allergen, should be excluded.
The more difficult diagnostic scenarios arise when
symptoms and signs are mild, subjective or atypical
(this is especially true for open oral food challenges). Further complicating the interpretation of

Table 14.8  Increased risk challenge scenarios

Condition

Rationale

Food protein-induced enterocolitis syndrome (FPIES)

Elective cannulation should be performed as patients are at risk of
dehydration due to excessive vomiting and/or diarrhea. Antiemetic
medications and rehydration fluids should be written up on
medication charts before commencing

History of severe anaphylaxis at the time of their index
reaction or severe coexisting asthma

May recur at time of subsequent challenge

Where pre-challenge allergy tests may be strongly
positive and suggestive of allergy, e.g. research settings

More is being learned about the predictive value of allergen
component tests in determining the risk of severe reactions, e.g. r Ara
h 2 may be such a marker for patients with peanut allergy47

Food-dependent exercise-induced anaphylaxis (FDEIA)
and exercise-induced anaphylaxis (EIA)

Elective cannulation should be performed beforehand as this may
prove difficult if performed for an exercise-induced reaction.
Nonetheless, exercise challenges have an excellent safety record

196

Oral Food Challenge Procedures

14

Table 14.9  Contraindications to oral food challenge (absolute and partial)

Contraindication

Reasoning

Absolute contraindications
Medical illness at time of challenge, e.g. viral
infection, poorly controlled asthma, uncontrolled
eczema

Uncontrolled asthma is a risk factor for severe food-induced allergic
reactions. Underlying illness may alter anticipated thresholds and
responses during the oral food challenge. Concurrent infections may
result in confusing non-allergic rashes. Severe eczema exacerbations may
result in false positive challenge outcomes

Underlying medical conditions where the treatment
of anaphylaxis may be compromised

Cardiac disease, or cardiac disease requiring use of a β-Blocker. ACEI may
be a cause of angioedema and this should be controlled for. NSAIDs,
particularly aspirin, may affect allergen absorption

Medication use that may mask allergic symptoms at
time of oral food challenge, e.g. antihistamines,
β2-agonists

Antihistamines may mask early signs of an allergic reaction. β2-agonists
may mask deterioration in lung function that would have been detected
at time of the oral food challenge

Partial contraindications
Individual is unwilling to continue eating the food in
the event of a negative result

Food allergy may ‘recur’ in patients who returned a negative oral
challenge but then continued to avoid the allergen

Poorly controlled rhinoconjunctivitis

Early signs of a food-induced allergic reaction commonly include
rhinoconjunctivitis, hence the presence thereof may confuse the
interpretation of challenge outcomes. In addition, symptom control may
depend on the use of antihistamines, which are contraindicated prior to
performing an oral food challenge

mild early-onset symptoms is the fact that these are
usually treated early on, which may interrupt the
progression to more severe unequivocal symptoms
and signs. Although safety is the primary concern
during such procedures it may be necessary to continue with the challenge when only mild symptoms
and signs are present. This is particularly true for
children with atopic eczema, who may over the
course of an oral food challenge develop nonspecific rashes, perhaps related to hospital-specific
factors, e.g. ambient temperature, bedding etc.
Despite the use of rigorous oral food challenge
outcome criteria, great emphasis should always be
placed on the experience of nurses and dietitians
who frequently perform oral food challenges. Their
clinical intuition, particularly when added to the
parents’ opinion, is often best at detecting early
symptoms or those that are non-specific, e.g. emotional and behavioral changes. Whereas older children may report a ‘feeling of impending doom’,
younger children and infants may become ‘suddenly quiet’ or ‘clingy’; a more subtle variation of
this is the ‘TV sign’, where young children who had
been entranced by electronic entertainment of
some sort suddenly lose interest and seek their
parents’ close attention.

More rigorous outcome criteria may be required
for research studies; we include the criteria used on
young children in the NIH-funded LEAP study
(Table 14.10).38

After the challenge
Oral food challenge outcomes should be described
as positive, negative or indeterminate – describing
challenge outcomes as ‘failed’ or ‘passed’ may be
emotive for children. The most common reason for
an indeterminate challenge result is being unable
to get the child to consume adequate quantities of
food to demonstrate tolerance. This situation may
be avoided in a number of ways. First, children
should only be challenged when they are old
enough for there to be a realistic expectation that
they can eat enough of the allergen. It is often necessary to disguise the challenge food, as previously
described. It is also worthwhile asking mothers to
omit the child’s breakfast and/or avoid giving
snacks during the early part of the challenge (when
doses are usually small), thus increasing their appetite at the time of the challenge.
It has been described that delayed biphasic allergic reactions can occur after the initial reactions,
197

Food Allergy
Table 14.10  Example of a scoring system for the diagnosis of immediate onset reactions (LEAP Study). A positive food
challenge should be made for children who experience one or more major criteria OR two or more minor criteria, an indeterminate
result is made if only one minor criterion is present, and a negative food challenge is made in the absence of any criteria.
Importantly, all symptoms should be of new onset and not due to ongoing disease. Symptoms must occur no later than 2 hours after
the last dose

Major criteria
Confluent erythematous pruritic rash
Respiratory signs (at least one of the following):
Wheezing
Inability to speak
Stridor
Dysphonia
Aphonia
≥3 urticarial lesions
≥1 site of angioedema
Hypotension for age not associated with vasovagal episode
Evidence of severe abdominal pain (such as abnormal stillness or doubling over) that persists for ≥3 minutes

Minor criteria
Vomiting
Diarrhea
Persistent rubbing of nose or eyes that lasts for ≥3 minutes
Persistent rhinorrhea that lasts for ≥3 minutes
Persistent scratching that lasts for ≥3 minutes

typically around 4 hours post ingestion. Therefore,
patients who react during a challenge should
remain under observation for at least 4 hours, or
longer if symptoms persist. Severe symptoms may
require overnight hospital admission. Education in
the identification and appropriate management of
allergic reactions in the event of accidental exposure
to the food, as well as strict dietary avoidance
advice, is required. Where the challenge is completed with no symptoms, patients should remain
for observation for at least 2 hours prior to the
challenge being considered negative. Again, they
should be given advice on the identification
and appropriate management of allergic reactions,
including late-phase reactions. They should also be
advised to reintroduce the food to their diet,
initially two to three portions per week, in an
attempt to ensure ongoing tolerance.4 This may
be particularly difficult for patients who are averse
to the food; a dietitian can help to advise on
alternative, more acceptable, forms of the food, or
even disguising it. Regardless of the initial outcome,
all patients should be reviewed 24 hours post challenge by telephone to eliminate delayed or ongoing
symptoms and to answer any questions that
typically arise.

198

Oral food challenges for the assessment
of non-IgE-mediated (delayed-onset)
food hypersensitivity
Non-IgE-mediated (delayed-onset) reactions can be
difficult to link to food ingestion owing to the delay
in symptom onset (hours to days after eating the
food) and the natural variability of the many conditions that may require an oral food challenge to
accurately assess for an influence of a food allergen
(see Table 14.2). Traditional allergy tests, such as
SPT and specific IgE determination, even when combined with atopy patch testing (APT), may be of
limited value; hence reliance is on elimination or
oligoallergenic diets, with the diagnosis confirmed
by a ‘reintroductory’ oral food challenge.39,40
Considerations associated with choice of challenge design (e.g. open or blinded), type of food,
placebo and doses for oral food challenges are as
described for IgE-mediated immediate-onset outcomes. The main differences lie in the duration and
location of the challenge and in the interpretation
of symptoms and signs. Oral food challenges are
usually unnecessary where an elimination diet
supervised by a dietitian has not resulted in an
improvement after 4 weeks, and the patient may

Oral Food Challenge Procedures

then slowly reintroduce that food. Where an
improvement does occur an oral food challenge is
recommended to rule out confounding factors and
confirm the diagnosis.39 Oral food challenges for
non-IgE-mediated food hypersensitivity usually
require repetitive provocation with the food over a
period of 2 and sometimes up to 7 days. If there is
no risk of immediate-type symptoms they may be
carried out in the patient’s home. It is important
that enough time is allowed for symptoms to
develop, e.g. late eczematous responses may take up
to 48 hours to develop.

Scoring of non-IgE-mediated
(delayed-onset) food hypersensitivity
allergic reactions
Where possible, delayed symptoms should be interpreted and scored systematically using validated
tools; these are best described for the outcome of
atopic eczema, which is by far the most common
non-IgE-mediated food hypersensitivity outcome
investigated for.

14

Atopic eczema
Food hypersensitivity is a known trigger for eczema,
particularly in infancy, and can result in immediatetype reactions, isolated late reactions (occurring
hours or 1–2 days after ingestion) or a combination
of the two.39,41 Open challenges are helpful to establish a causative relationship between the food and
eczema, especially for negative outcomes. For subjective outcomes use is made of DBPCFCs. Ideally,
an oral food challenge would only be initiated
when the patient’s eczema is well controlled. Reducing the natural fluctuations of the eczema assists
with clinical evaluation of the skin post challenge.
However, in clinical practice it is the patient with
severe and difficult to control eczema who typically
undergoes this diagnostic testing. The procedures
involved in an oral food challenge for atopic eczema
are summarized in Table 14.11.
Where more than one food has been eliminated,
and immediate-type reactions are not expected, a
stepwise reintroduction of these foods could be
carried out over a period of a few weeks. A new food
group can be reintroduced and then retained in the

Table 14.11  Oral food challenge in atopic eczema
Prior to
challenge

Strict elimination diet of the ‘candidate’ allergen/s for 4 weeks, under the supervision of a dietitian*
Ensure best possible eczema control prior to initiating challenge
Antihistamines withdrawn at least 3–10 days before challenge

i)  Open
challenge

Repetitive provocation with the same food for at least 2 days is advised with patients observed for at least
48 hours following the challenge31

ii)  Blinded
Challenge

Day 1**

Active challenge food: incremental delivery of total daily dose

Day 2**

Active challenge food: cumulative delivery total daily dose

Day 3

Observation

Day 4

Observation

Day 4***

Placebo: incremental delivery of total daily dose

Day 5***

Placebo: cumulative delivery total daily dose

Day 6

Observation

Day 7

Observation

Post
challenge

Scoring of delayed symptoms. Clinical evaluation must be uniform throughout the period, e.g. SCORAD to assess
eczema severity. An increase of 10 SCORAD points or more indicates a significant deterioration of eczema;
however, such changes may be less significant when initiating the challenge at times when the baseline SCORAD
is moderate or higher, i.e. 40 points31

*Oral food challenges are usually unnecessary where an elimination diet has not resulted in any improvements after 4 weeks, and the patient may
then slowly reintroduce that food.
**Daily dose is equivalent to age-related average daily intake of that food; appropriate typical daily dose e.g. 20 oz (600 mL) cows’ milk formula for
an infant.
***In the case of DBPCFC, the active challenge food and placebo should be given on two or more consecutive days, in random order, with a 1-day
interval between placebo and active challenge. Where an immediate-type reaction is suspected these should be given in an incremental fashion,30
e.g. 7–8 doses.

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Food Allergy
Table 14.12  Confounding oral food challenge factors

Confounding oral
food challenge factors

Controlled for by:

Exercise

If indicated, perform oral food challenges while controlling for exercise, i.e. with
and without prior food ingestion

Medications, e.g. aspirin

Before the challenge avoid medications that may influence or mask the outcome
of the allergic reactions

Alcohol

Avoid alcohol ingestion prior to oral food challenges

Emotional stress

Avoid periods of high emotional stress and anxiety

Hormonal cycles

Record hormonal status

Infection

Oral food challenges should only be performed when the subject is in good health

diet every 4 days, with observation for a deterioration of the skin. Whether this occurs at home or in
the hospital setting, it should be carefully assessed
by an experienced allergy team, as severe allergic
reactions have been reported in children with
atopic dermatitis upon reintroduction of a food
after following an elimination diet for a longer
period.42

Modified oral food challenges
It may be that additional factors are required to
alter oral food challenge outcomes; examples
include hormonal cycles, medications such as
aspirin, exercise, emotional stress, and even infection (Table 14.12). Observations from specific oral
tolerance induction studies confirm the concept
of dose-dependent tolerance and tolerance that
is influenced by one or more of the above-listed
confounding factors.43 Modified oral food challenges, and challenges tailored for the diagnosis of
the food protein-induced enterocolitis syndrome
(FPIES), deserve special mention.

Food protein-induced
enterocolitis syndrome
The FPIES represents a cell-mediated gastrointestinal food hypersensitivity usually diagnosed in
infancy. The syndrome is characterized by
protracted diarrhea and/or vomiting and is frequently associated with additional symptoms such
as pallor and/or lethargy.44 Symptom onset varies
from 1–2 hours after the ingestion of the causative
food protein, but may occur up to 10 hours later.
Presentation varies from mild (e.g. non-dehydrating
200

vomiting and/or diarrhea) to severe; indeed,
hypovolemic shock is associated in up to 20% of
cases. In patients with a history of severe reactions
a starting dose of 0.06  g/kg of the challenge food
is recommended.45 As immediate-onset reactions
are not anticipated, the entire portion may be
administered gradually in three feedings over a
period of 45 minutes. Patients should then be
observed for at least 4 hours to allow for delayed
presentations. Additional safety precautions are as
in Table 14.8.

Food–exercise challenges
Exercise-induced anaphylaxis (EIA) is a rare condition where one or more factors associated with
exercise results in anaphylaxis. Subclassifications
include ‘pure’ EIA and food-dependent exerciseinduced anaphylaxis (FDEIA). Although EIA occurs
independently of food, the clinical syndrome of
FDEIA is typified by the onset of anaphylaxis during
(or soon after) exercise which was preceded by the
ingestion of the causal food(s). In FDEIA, both the
food allergen and exercise are independently tolerated. To diagnose and differentiate the above conditions, use is made of modified oral food challenges
such as open food–exercise challenges (OFEC) and
the double-blind placebo-controlled food–exercise
challenge (DBPCFEC).46 During modified food–
exercise challenges patients are asked to eat the
suspected food allergen prior to exercise. Confounding factors unique to the patient’s presentation may be required to reproduce FDEIA, e.g.
particular forms of exercise or extreme environments. Therefore, although logistically difficult, a
more ideal food–exercise challenge is for the patient

Oral Food Challenge Procedures

to repeat the exercise under similar environmental
conditions to that which induced the index
reaction.
It is important that all food challenge patients be
followed up (either in clinic or by telephone) for
the scoring of delayed symptoms, as it is not uncommon for delayed symptoms, e.g. eczema exacerbation, to develop even after an oral food challenge
performed for the primary purposes of diagnosing
an immediate-onset IgE-mediated food allergy.

Summary
Food challenges remain the gold standard investigation for the diagnosis and management of immediate and delayed food-induced allergic reactions
and are essential to contemporary allergy practice.
The clinician should aim to achieve a 50% positive to negative outcome ratio when performing oral
food challenges in patients with established allergies. This is achieved by careful patient selection.
Oral food challenges are used to confirm a diagnosis of allergy – or tolerance – where this is uncertain based on detailed history and allergy diagnostic
tests. Tolerance may be confirmed by oral food
challenges in the following situations: where an
allergy is suspected to have been outgrown; when
allergy tests suggest tolerance but the food has
never been eaten; when a food is suspected to cause
delayed allergic symptoms; or to clarify allergy in
cases of cross-reactivity. Allergy may be confirmed
by oral food challenges where the cause of a suspected food allergic reaction is uncertain or where
equivocal or inconsistent symptoms occur following the consumption of a particular food. Other
uses include the establishment of thresholds of
reactivity and to monitor immunomodulatory
treatments. Whereas a positive oral food challenge
ensures appropriate allergen avoidance, a negative
challenge results in safe dietary expansion.
Challenge designs exist that are adaptable for use
in both research and clinical settings and can be
individualized to the patient so as to maximize the
reliability of the challenge outcome and minimize
risk. Variations include open or blinded challenges,
with or without the inclusion of placebo foods.
Adjustments can also be made to initial and top
doses and the choice of challenge food, depending
on the indication for the challenge and the patient’s
circumstances.
After a negative challenge it is essential that
patients are advised about late-phase reactions and

14

how to treat them, as well as how to introduce the
food into their diet. This may be difficult for those
who are averse to the food and may require the
skills of an experienced dietitian to identify suitable
alternatives. Ongoing consumption of the food is
important to avoid a possible risk of loss of tolerance to that food. Following a positive challenge,
patients should be given advice on medical management in the event of accidental exposure, as well
as dietary advice to facilitate careful avoidance of
the food.
When performed by an experienced healthcare
team, oral food challenges are safe and remain
a valid and extremely helpful diagnostic modality
essential to the everyday practice of allergy
management.

Food Challenge Procedures
Prior to challenge
Assessment of suitability for food
challenge
OFC is indicated to confirm allergy or tolerance
to challenge food (see Table 14.2)
No reactions to challenge food in last year
Patient agrees to introduce the food if the
challenge is negative
Patient is old enough to complete the challenge
Patient is well enough to undergo challenge
procedure
Patient understands the procedure and gives
consent (or parent/carer in case of children)

Assessment on arrival for challenge
Review history of reactions to challenge food,
including severity
Carry out physical examination and review
medical history to confirm fitness for
challenge
Carry out baseline observations: weight, height,
temperature, pulse, respirations, oxygen
saturations, blood pressure, and peak
expiratory flow rate
Confirm all relevant medications stopped prior to
challenge as appropriate
Explain procedure and obtain consent from
patient (or parent/carer in case of children)
Decide if high or low risk challenge and cannulate
if required
201

Food Allergy

Preparation for challenge
Carry out safety checks, e.g. check oxygen and
suction in working order
Ensure emergency medications available and
drawn up for high risk challenges
Weigh out challenge doses as below; add masking
ingredients if required. NB: these must be
ingredients previously tolerated by the patient
Take precautions to avoid cross-contamination

Challenge procedure
During the challenge: record all observations,
time doses given, amount of each dose given
Carry out baseline observations: temperature,
pulse, respirations, oxygen saturations, blood
pressure, and peak expiratory flow rate
Smear a small amount of challenge food unto lips
and oral mucosa. Do not smear onto obvious
patches of peri-oral eczema or areas of the
body affected by eczema as this may induce
localized skin reactions. Some protocols do
not include a lip dose and proceed to Dose 1.
Wait at least 15 minutes and repeat observations
Give dose 1 and wait at least 15 minutes. Repeat
observations prior to next dose.
Continue as above, giving other doses until the
top dose has been given and tolerated.

If there are signs of a reaction
Stop the challenge immediately
Administer treatment according to severity of
the reaction

Observations should be repeated and patient
monitored closely
If the symptoms do not meet the criteria (Table
14.10) for a positive challenge, pause until
symptoms resolve then continue with the
next challenge dose

Post challenge
Following a positive challenge
Patients should remain for observation for at least
4 hours after the challenge or until symptoms
have resolved. For severe symptoms patients
may need to be admitted overnight
Provide education in the identification and
appropriate management of allergic reactions
Dietitian to advise on strict dietary avoidance of
the food
24 hours post-challenge review by telephone to
eliminate delayed symptoms

Following a negative challenge
Patients should remain for observation for at least
2 hours after the challenge has been
completed
Provide education in the identification and
appropriate management of allergic reactions,
including late-phase reactions
Dietitian to advise on reintroduction of the food,
particularly in those who are averse to it
24 hours post-challenge review by telephone to
eliminate delayed symptoms
For doses see Table 14.13 and Table 14.14.

Table 14.13  Example 1. Open incremental challenge to peanut

Dose

Amount of challenge food: peanut or
peanut butter (g)

Peanut protein
equivalent (g)*

Lip dose

Rub half a peanut or smear fingertip amount
peanut butter on lower lip

Trace

Dose 1

0.5

0.125

Dose 2

1.0

0.25

Dose 3

2.0

0.5

Dose 4

4.0

1.0

Dose 5

10.0

2.5

Dose 6

20.0

5.0

*Slight differences exist in the peanut content of peanuts vs peanut butter.

202

Oral Food Challenge Procedures

14

Table 14.14  Example 2. DBPCFC to peanut

Design

Dose

Amount of
challenge food (g)

Peanut protein
equivalent (g)

Chocolate muffin*
Blind

Active dose 1

1.6

0.1**

Active dose 2

4

0.25

Active dose 3

8

0.5

Active dose 4

16

1.0

Active dose 5

40

2.5

Placebo doses may be randomly interspersed with active doses or given during a separate session
later the same day or on a different day
Open

Open dose

Peanut butter (20 g) sandwich or 25
whole peanuts

5.0

*40 g muffin containing 5 g peanut flour or 2.5 g peanut protein.
**Use initial challenge dose of 0.1 mg for high-risk challenges.5

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effects of roasting on the allergenic properties of
peanut proteins. J Allergy Clin Immunol 2000;
106(4):763–8.
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21. Grimshaw KE, King RM, Nordlee JA, et al. Presentation
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nature of the allergic reaction–a case series. Clin Exp
Allergy 2003;33(11):1581–5.
22. Van Odijk J, Ahlstedt S, Bengtsson U, et al.
Doubleblind placebo-controlled challenges for peanut
allergy the efficiency of blinding procedures and the
allergenic activity of peanut availability in the recipes.
Allergy 2005;60(5):602–5.
23. Carpenter RP, Lyon DH, Hasdell TA. Guidelines for
sensory analysis in food product development and
quality control. •• 2000:36–43.
24. Vlieg-Boerstra BJ, Herpertz I, Pasker L, et al. Validation
of novel recipes for double-blind, placebo-controlled
food challenges in children and adults. Allergy 2011
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guidelines. WAO Journal 2010:57–161.
26. Vlieg-Boerstra BJ, Bijleveld CM, van der HS, et al.
Development and validation of challenge materials
for double-blind, placebo-controlled food challenges
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341–6.
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Placebo reactions in double-blind, placebo controlled
food challenges in children. Allergy
2007;62(8):905–12.
28. Hourihane JO’B, Kilburn SA, Nordlee JA, et al. An
evaluation of the sensitivity of subjects with peanut
allergy to very low doses of peanut protein: a
randomized, double-blind, placebo-controlled food
challenge study. J Allergy Clin Immunol
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29. Flinterman AE, Pasmans SG, Hoekstra MO, et al.
Determination of no-observed-adverse-effect levels and
eliciting doses in a representative group of
peanutsensitized children. J Allergy Clin Immunol
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in double-blind, placebo-controlled oral food
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reactions during peanut oral immunotherapy home
dosing. J Allergy Clin Immunol 2009;124(6):1351–2.
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enterocolitis syndrome. Curr Opin Allergy Clin
Immunol 2009;9(4):371–7.
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features of food protein-induced enterocolitis
syndrome. J Pediatr 1998;133(2):214–9.
46. Du Toit G. Food-dependent exercise-induced
anaphylaxis in childhood. Pediatr Allergy Immunol
2007;18(5):455–63.
47. Nicolaou N, Poorafshar M, Murray C, et al. Allergy or
tolerance in children sensitized to peanut: prevalence
and differentiation using component-resolved
diagnostics. J Allergy Clin Immunol
2010;125(1):191–7.

CHAPTER

15 

Management of Food Allergy and
Development of an Anaphylaxis
Treatment Plan
Jacqueline Wassenberg and Philippe Eigenmann

Introduction
This chapter will develop the various aspects of
food allergy management, including the treatment
of acute reactions, a personalized food allergy
management plan to prevent and treat recurrences,
and finally suggest preventive strategies in the
community.
Epinephrine remains the drug of choice for the
treatment of any anaphylactic reaction, the lifethreatening complication of food allergy. After
allergy work-up of the initial reaction, food elimination is the only actually available treatment in
daily life.
Although these treatment options are well established, there are some limitations to applying the
principles of evidence-based medicine to the management of food allergy, in particular to anaphylaxis, owing to the unpredictability of the episodes,
to episodes commonly occurring in the community
rather than in healthcare settings, and to the variability of signs and symptoms, pattern, severity and
duration of episodes.1 Obtaining randomized
placebo-controlled data to evaluate a therapeutic
intervention is difficult, because of unethical delays
and the use of placebo in treating a condition that
is life-threatening. Consequently, most of the actual
evidence for the long-term risk reduction of acute
episodes of food allergy are based on consensus
and opinion (grade C) or at best on well-designed
© 2012, Elsevier Inc

studies but not randomized controlled trials
(grade B).2
As described in Chapter 4, a wide range of
symptoms ranging from atopic eczema to severe
life-threatening anaphylaxis are common clinical
features of food allergy. Proper management should
be adapted to the clinical expression and based on
the risk assessment of future reactions. The age of
the patient, the foods involved, the presence of
comorbidities – such as asthma – and the social
environment are important factors to take into
account when establishing a management plan.
Dietary elimination, the prescription of epinephrine autoinjectors and the fear of potential lifethreatening reactions have a clear impact on quality
of life.3 Regular reassessment of the management
plan should also take this aspect into account in
order to improve adherence to the medical advice.
Quality of life of patients and their families can be
evaluated and reassessed by food allergy-specific
validated quality of life (QoL) questionnaires.
Avery et al.4 compared the impact of food allergy
and insulin-dependent diabetes mellitus (IDDM)
by using disease-specific QoL questionnaires. Children suffering from food allergy showed significantly worse QoL scores than those with IDDM.
Proper food allergy management implies a specialized and up-to-date follow-up, from the diagnosis of food allergy to implementation in the
community by education of childcare providers.

Food Allergy

Management of acute reactions
Clinical manifestations
Symptoms of IgE-mediated food allergy mostly
occur within 30 minutes after exposure to the food.
Cutaneous signs are most often present, especially
in childhood. Pruritus, more specifically of the
palms, feet and head, may be an early sign of a
progressive acute reaction. However, it should be
highlighted that anaphylaxis can occur in the
absence of cutaneous manifestations.
Acute early manifestations often include acute
rhinorrhea, itching of the eyes, lips and ears or
facial edema. In children, life-threatening reactions
are most often associated with bronchospasm.
Upper airways symptoms related to laryngeal edema
might also reveal a potentially severe progressive
reaction. Hypotension and cardiovascular shock are
less common in children than in adults; they can
be accompanied by a sensation of light-headedness
and loss of consciousness. Abdominal signs, such
as severe abdominal pain, vomiting and/or diarrhea,

are commonly present in children and can herald
a severe anaphylactic reaction.
Expert panels5,6 have proposed a severity score to
ensure the diagnosis of anaphylaxis and the appropriate indication to inject epinephrine (Table 15.1).

Epinephrine administration
Rapid initiation of treatment is crucial, as one of
the identified risk factors for death is the delay of
epinephrine administration. Series of fatalities
described by Pumphrey et al.7 show that death
occurs most often within 25–30 minutes after
ingestion (from 10 minutes to 6 hours).
International and national guidelines recommend epinephrine as the first-line treatment in an
acute episode.8 It should always be administered in
case of an anaphylactic reaction involving either the
respiratory tract or in case of cardiovascular signs.
Epinephrine increases peripheral vascular resistance, blood pressure and coronary perfusion,
while reducing angioedema and urticaria, by an
α-adrenergic effect. Its β1-adrenergic effect increases

Table 15.1  Grading of severity of anaphylactic reaction5,6

Grade

Severity

Skin

GI tract

Respiratory

Cardiovascular

Neurological

1

Mild

Sudden
itching of
eyes and
nose,
generalized
pruritus,
flushing,
urticaria or
angioedema

Oral pruritis,
oral ‘tingling’,
mild lip
swelling,
nausea or
emesis or
mild
abdominal
pain

Nasal congestion
and/or sneezing,
rhinorrhea, throat
pruritus, throat
tightness or mild
wheezing

Tachycardia
(increase >15
beats/min)

Change in
activity level and
anxiety

2

Moderate

Any of the
above

Any of the
above, and
crampy
abdominal
pain,
diarrhea or
recurrent
vomiting

Any of the above,
and hoarseness,
barky cough,
difficulty
swallowing,
stridor, dyspnoea
or moderate
wheezing

As above

‘Lightheadedness’,
feeling of
‘pending doom’

3

Severe

Any of the
above

Any of the
above, and
loss of bowel
control

Any of the above,
and cyanosis or
saturation <92%,
or respiratory arrest

Hypotension*
and/or collapse,
dysrhythmia,
severe
bradycardia and/
or cardiac arrest

Confusion, loss
of consciousness

*Hypotension defined as systolic blood pressure: 1 month to 1 year <70 mmHg; 1–10 years <[70 mmHg + (2 × age)]; 11–17 years <90 mmHg.
The severity score should be based on the system most affected. Symptoms and signs in bold are indications for the mandatory use of adrenaline.

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Management of Food Allergy and Development of an Anaphylaxis Treatment Plan

Table 15.2  Indications for the administration
of epinephrine in the emergency room or
in the community

Mandatory
if …

Consider adrenaline
administration if …

• Respiratory
distress
• Hypotension
• Collapse

Skin, mild gastrointestinal
symptoms
and
Asthma
Previous severe reaction
Exposure to known/likely allergen





the heart rate and myocardial contraction, and its
β2-adrenergic effects induces bronchodilation and
inhibits the release of inflammatory mediators.6
The use of epinephrine should take into account
who will administer it, i.e. physicians in the emergency room, or parents or the patient himself. In
case of a previous severe reaction with a rapid onset,
epinephrine should be administered without delay.
Earlier use is also justified in patients with asthma,
identified as another major risk factor for anaphylaxis fatality (Table 15.2).6

Contraindications for epinephrine
administration
Coronary heart diseases and cardiac arrhythmia
are relative contraindications for administering
epinephrine. In patients with these coexisting
conditions the risks and benefits of epinephrine
should be evaluated, taking into consideration that
it can be life-saving in anaphylaxis. In children,
apart from rare comorbidities such as hypertrophic
obstructive cardiomyopathy associated with tachyarrythmia, there are no contraindications to
epinephrine administration.

Routes of administration and dosage
of epinephrine
Intramuscular injection should be preferred both in
the community and in the emergency room. Epinephrine injected into the muscle is rapidly bioavailable, with peak concentrations reached within 10
minutes, and has a much better safety profile than
intravenous administration. Subcutaneous injection results in significant vasospasm, which prevents
the diffusion of epinephrine into the blood vessels.
The preferred injection site is the lateral side of
the thigh (vastus lateralis muscle). Obese patients

15

should be instructed to use the autoinjector in a
place where the thickness of the subcutaneous
tissue does not exceed 14.3 mm, the usual length
of the needle.9
The therapeutic range of epinephrine is narrow,
implying that under- and over-dosage should be
carefully avoided. The usually accepted intramuscular dose for self-treatment in adults is 0.3 mg of
epinephrine 1 : 1000 (1 mg/mL). For children,
autoinjectors have a fixed dose of 0.15 mg. In an
emergency setting, the appropriate pediatric dose is
0.01 mg/kg of body weight, with a maximum single
dose of 0.3–0.5 mg. Injections can be repeated every
5–10 minutes until the patient reaches a stable condition. The use of intravenous epinephrine should
be limited to severe situations, with administration
of 0.1 µg/kg/min under close monitoring.

Other medications
H1 antagonists
H1 antagonists can be given if a patient develops
mild clinical symptoms such as skin symptoms.
However, it needs to be emphasized that H1 antagonists have no proven efficacy in the treatment of
anaphylaxis.10 In addition, the administration of H1
antagonists should never delay the administration
of epinephrine. Oral forms of H1 antagonists are
most often preferred as they are non-sedating and
long-lasting. The dose should be adapted to the
weight of the patient. Rapid-onset H1 antagonists
(diphenhydramine or chlorpheniramine) are also
available for intravenous injection, but these two
first-generation H1 antagonists have a much higher
sedative side effect than the second-generation H1
antagonists. Their use should be limited to situations in which oral treatment is not available.

Corticosteroids
Corticosteroids should not be considered as a firstline treatment in anaphylaxis. The onset of action
is within hours of administration, and they are
often used to prevent relapses. However, there is no
proven efficacy in the prevention of long-lasting or
biphasic reactions.11

Inhaled β2-agonists
An inhaled β2-agonist, with the use of a spacer
or a nebulizer, can be helpful if bronchospasm is
associated. However, inhaled β2-agonists remain a
207

Food Allergy

second-line treatment in case of anaphylaxis. In
addition, proper penetration to the airways can be
reduced by acute bronchospasm. Uncontrolled or
partially controlled asthma is a risk factor for severe
anaphylaxis, implying that optimal asthma control
should be a high priority in these patients.

Support medication
The severe reactions of food allergy can involve the
cardiovascular system and may lead to tachycardia
and decreased blood pressure. In these cases intravenous fluids should be added to epinephrine,
starting with normal saline 20 mL/kg body weight,
a dose which can be repeated. It has been shown
that the need for volume expanders as well for more
than one dose of epinephrine was a predictor for
biphasic reactions. In addition, high-flow oxygen is
essential in all patients with respiratory or cardiovascular symptoms.
After initial emergency treatment, patients with
severe anaphylaxis should be monitored for 24
hours in an appropriate medical facility. With less
severe reactions without respiratory or cardiovascular impairment, an observation time of 3–4 hours
in the emergency room should be sufficient. In any
case, a patient should be discharged from the emergency room only when the physician is fully convinced that the allergic reaction has resolved.

Comorbidities affecting the treatment
of anaphylaxis
Different pharmacologic substances may either
impair the efficacy of epinephrine or increase its
potential side effects. A non-exhaustive list includes
tricyclic antidepressants, cocaine (cardiac arrhythmia) and β-blockers (which inhibit the sympathetic
effects of epinephrine).
An increased risk of fatal reactions has been associated with recent asthma exacerbations and/or
overuse of short-acting β2-agonists as well as to suboptimal long-term asthma management. Most
deaths due to food allergies were found to be associated with bronchospasm and mucous plugging of
the bronchioles.7
Exercise is a potential cofactor of severe food
allergy; it could be related to increased blood
flow, or increased non-allergen-induced mast cell
degranulation. Ingestion of non-steroidal antiinflammatory agents (NSAIDs) can also lower the

208

threshold for mast cell degranulation and hence
increase the severity of the reaction.
Ingestion of alcoholic beverages has been associated with severe food-induced allergic reactions,
possibly due to an increasing absorption, or to an
increased risk of accidental food ingestion.
Patients with mastocytosis, a rare disease associated with increased mast cell degranulation, may
experience severe anaphylactic reactions.
Finally, moving from a supine to an upright position during anaphylaxis has been associated with
cardiac arrest due to a sudden drop in blood pressure, implying that patients with severe foodinduced anaphylaxis should be kept in a lying
position.

Emergency room protocols for severe
reactions (Fig. 15.1)6
Airways, breathing and circulation should be first
assessed and regularly re-evaluated. Repeated injections of epinephrine are indicated until adequate
clinical stabilization is achieved, e.g. every 10–15
minutes. Patients with respiratory symptoms should
be monitored for at least 6–8 hours and those with
cardiovascular involvement for at least 24 hours –
as previously mentioned – before discharge.
Patients should be instructed to avoid potentially
implicated allergens until the appropriate diagnostic allergy work-up. In addition, epinephrine
autoinjectors should be adequately prescribed, and
patients should be trained in their proper use.
It should be emphasized that allergy work-up
needs to include education, which will be addressed
in the next section.

Long-term anaphylaxis management
Identifying the causal factor
Patients with a history of a reaction suggestive of
food allergy will need a full diagnostic work-up in
order to prevent further reactions. Evaluation
should be based on the history of the reaction,
identifying the foods eaten during the preceding
2–4 hours. Work-up should include identification
of hidden allergens (by reading labels) or ‘new
foods’ (foods locally not consumed until recently,
or new processing methods of known foods) (see
Clinical Case 1). The presence of comorbidities and

Management of Food Allergy and Development of an Anaphylaxis Treatment Plan

Call for HELP

ABC

Respiratory distress,
hypotension or collapse
GIVE I.M. EPINEPHRINE

Hypotension or collapse
• High flow oxygen
• Normal saline or colloid 20 mL/kg I.V./I.O.
• I.V./I.O./I.M. antihistamine
• (I.V./I.O. corticosteroid)

If no response in 5–10 minutes
• Repeat I.M. epinephrine
• Repeat fluid bolus
• Set up I.V. epinephrine (infusion)

15

Consider I.M. epinephrine if:
• Previous severe reaction
• Exposure to known/likely allergen
• Coexistent asthma

Stridor
• High flow oxygen
• (Nebulized Epinephrine)

Wheeze
• High flow oxygen
• Nebulized beta-2-agonist

If no response in 5–10 minutes
• Repeat I.M. epinephrine
• Nebulized corticosteroids
• I.V. access

If no response in 5–10 minutes
• Repeat I.M. epinephrine
• I.V. access

Figure 15.1  Example of the plan for initial treatment of children with anaphylaxis in the emergency room.

conditions mimicking food allergy should be considered. As outlined in Chapter 13, the allergy
work-up will be conducted based on the clinical
history, including specific serum IgE measurement,
skin prick tests and, if needed, oral food challenges
(see Chapter 14). Unnecessary food elimination
diets, based on the history alone or the fear of
potentially ‘dangerous’ foods, can cause unnecessary psychological troubles and social exclusion.3

CLINICAL CASE 1
A healthy but atopic 8-year-old boy with cat and grass
pollen allergies presented with a sudden nasal discharge
and watery eyes followed by facial edema and difficulty
breathing, 30 minutes after eating a waffle in the
playground. He had no history of food allergy or
previous anaphylactic reactions, and was on a normal
diet, including consumption of peanuts and other
legumes. The factory-produced waffle contained eggs,
sugar and lupin flour. The child was brought to the
emergency room, where within 15 minutes he was given
IV antihistamines and steroids, but no epinephrine was
administered.
The allergy work-up showed skin prick tests positive to
peanut but negative to soy, eggs, nuts (walnut, hazelnut,
almond) and other legumes (chickpea and lentil). A prick
test with native lupine flour diluted in a saline solution was
strongly positive. Total IgE was 1237 UI/mL. Specific IgE
antibodies were positive to lupin seeds (20.8 kU/L, norm:

<0.35 kU/L) and peanut (>100 kU/L, norm: <0.35 kU/L)
(UniCAP, Phadia, Uppsala, Sweden). A diagnosis of
anaphylaxis to lupin flour and a strong sensitization to
peanuts was established. An oral challenge was not
performed in this child with a history of a severe reaction.
The patient was instructed to strictly avoid lupin flour and
seeds, as well as peanuts. Self-injectable epinephrine and
oral cetirizine were prescribed in case of an accidental
allergic reaction. Subsequent severe reactions due to
accidental lupin ingestion occurred, thereby confirming
the diagnosis. His food allergy management plan was
regularly reassessed.

Discussion
An unusual food, lupin flour, triggered this severe allergic
reaction. Lupin has been cultivated for more than 4000
years all over the world. It is closely related to chickpea,
green pea, soy and peanuts. Lupin flour has a high protein
content and offers monounsaturated fatty acids; it is a
gluten-free flour. Because of its nutritional values and
culinary qualities (good color, better conservation and
softness), lupin is increasingly used in the preparation of
industrial food (pizzas, cakes, vegetarian food, sausages).
Depending on the national regulations, lupin flour or lupin
seeds – like other rare or new foods – are not always listed
on food labels, unlike major allergens which must be
listed. Therefore, individuals with rare food allergies are at
increased risk of accidental ingestion, especially when
eating manufactured products.

209

Food Allergy
This child with a highly positive test to peanuts was
advised to avoid this food as well.
When the patient was initially treated, no written
standardized food allergy management plan was available
and he and his carers were advised orally when and how
to use his epinephrine autoinjector. Owing to this lack of
labeling and the absence of a written food allergy
management plan, the patient had subsequent severe
reactions.
It might also be noted that this child did not receive
epinephrine in the emergency room, which highlights the
low awareness of the indication to administer epinephrine
in case of anaphylaxis.

Proper food elimination
Fatal food-induced anaphylaxis has been reported
even after correct use of epinephrine, therefore adequate food elimination remains the first-line advice
for patients with food allergies.9
Correct advice for food avoidance will need to be
adjusted to the age, type of food, social activities,
living conditions and occupation of the patient, as
well as to school and school catering settings, or to
daycare centers.
Patients and their families should be informed
about the symptoms as well as the severity of reactions to be expected in case of accidental ingestions,
skin contact or inhalation of the allergens. They
must also be instructed on how to read labels, a
task which can be difficult due to the various terms
for a specific allergen (for example either ‘peanut’
or ‘arachis’), to the variety of authorized contamination thresholds between countries, and to the
presence of warnings such as ‘may contain …’.12
They should also be aware of the possible presence
of hidden allergens and situations of high risk for
accidental ingestions, such as restaurants, or the
homes of friends or relatives. Based on the UK Register of fatal reactions it has been shown by Pumphrey,7 that one-third of fatalities due to food
allergy occur at home, 25% in restaurants and the
remainder in nurseries/schools/at work (15%) and
at relatives’ homes (12%). In the case of multiple
food allergies, counseling by a dietitian knowledgeable in food allergy can provide very useful information on the minimal daily requirements for
essential nutrients, food replacements, i.e. for home
cooking of baked products, and proper reading of
food labels. This topic will be more precisely
addressed in Chapters 16 and 19. In principle,
yearly follow-up visits, especially in children, are
important in order to reassess the current list of
210

Table 15.3  Special conditions increasing the risk of
severe reactions
Specific foods: peanuts and tree nuts
Reactions to traces of foods
Asthma
Adolescence
Exercise
Cocaine or alcohol consumption
Medications such as β-adrenergic blockers, tricyclic
antidepressants

allergies, accidental ingestions and their consequences in the past months, as well as to advise on
minimal impact on daily activities. Such visits have
been shown to reduce the rate and severity of
reactions.13,14

Management of specific conditions
(Table 15.3)
As previously mentioned, there are some conditions that may increase an individual’s risk of severe
reactions.
A few foods, mostly peanuts and tree nuts, are
responsible for the majority of severe or fatal reactions.15 Patients reacting to traces of food are especially at risk for severe reactions and may also react
to inhalation of allergens. These patients should be
instructed to strictly avoid the food.
Although previous severe reactions predispose to
severe or potentially fatal reactions, these might
appear in patients with previously mild reactions,
or at the initial episode.
Most fatalities due to food allergy are reported in
children suffering from asthma, in particular
patients with partially controlled or uncontrolled
asthma, with a history of recent exacerbations, and
recent stepping down of or non-compliance with
treatment. In case of food allergy and asthma –
common conditions that are frequently associated
– asthma control must be regularly assessed and the
risks of stepping down treatment carefully balanced
against its benefits.6
Adolescence is a period that has been associated
with severe food-induced reactions, mostly due to
increased risky social behaviors, poor drug compliance and denial of food allergy. A specific follow-up
especially designed for adolescents with food allergies is most helpful.
Patients should be informed of potential risk
factors such as exercise, cocaine addiction, alcohol

Management of Food Allergy and Development of an Anaphylaxis Treatment Plan

consumption or specific medications – as previously mentioned – which can increase the severity
of the reactions or diminish the responsiveness to
treatment.

Self-injectable epinephrine and
personalized treatment plans
Despite optimal food elimination diets and longterm measures to reduce the risk of accidental
ingestion, food-induced allergic reactions can recur,
with symptoms even more severe than previously.
Individuals, their families and their carers should
be able to recognize an allergic reaction and to
treat it.
The decision to prescribe an epinephrine autoinjector involves analyzing the risks of anaphylaxis,
the potential benefits of rapid administration of
epinephrine, the risks associated with carrying an
autoinjector, and the cost to the health service or
the individual family.

Who should be prescribed a self-injectable
epinephrine device?
Based on current knowledge, the European
Academy of Allergy and Clinical Immunology
guidelines on anaphylaxis gives a list of four absolute indications to prescribe a self-injectable device
(Table 15.4):6



A previous cardiovascular or respiratory
reaction to a food (and to other allergic
triggers such as insect sting or latex)

Table 15.4  Indications for prescribing a self-injectable
epinephrine device

Absolute indications

Relative indications

A previous cardiovascular
or respiratory reaction to
a food (and to other
triggers such as insect
sting or latex)

Any reactions to small
amounts of a food
including airborne or
contact of the food
allergen only via skin

Exercise-induced
anaphylaxis (often related
also to food)

History of previous –
even mild – reactions to
peanut or tree nuts

Idiopathic reactions

Remoteness of home
from medical facilities

Child with food allergy
and asthma

Food-allergic reaction in
a teenager

15



Exercise-induced anaphylaxis (often also
related to foods)
• Idiopathic reactions
• A child with food allergy and asthma
as well as four relative indications:



Any reactions to small amounts of a food,
including airborne or contact only via the skin

History
of previous – even mild – reactions to

peanut or tree nuts
• Remoteness of home from medical facilities
• Food-allergic reaction in a teenager.
As already mentioned, asthma is the most common
risk factor for death due to food allergy, and is
therefore defined as an absolute indication.
It should be emphasized that two studies evaluating the degree of severity of recurrences in tree nutand peanut-allergic patients show that, even in
mild reactions in children, the risk of anaphylaxis
can reach 31% over a 6-year median period of
follow-up.15,16 This would suggest the need for all
children with tree nut and peanut allergy to be
prescribed self-injectable epinephrine. Unfortunately, similar data are not yet available for other
foods. Deaths due to food allergy are mainly linked
to tree nuts and peanut, but can also occur with
milk and fruits. Known histories of reactions prior
to the fatality are mainly described as mild, and the
amount ingested is very variable, ranging from
traces to several grams of dry food.7
Adolescence is another risk factor for severe reactions and has been listed as a relative indication for
the prescription of self-injectable devices.
Food-induced flares of atopic dermatitis in the
absence of more severe symptoms, and symptoms
limited to the oral mucosa (oral allergy syndrome)
are not an indication for the prescription of selfinjectable epinephrine.

Which device should be prescribed?
Various devices are available in many countries.
They are preset to administer a fixed dose, either
0.15 mg (‘junior’) or 0.3 mg of epinephrine. The
0.15 mg devices are commonly indicated for children from 15 to 25 kg body weight and the 0.3 mg
devices for individuals of 25 kg and more. There is
no self-injectable device for infants under 15 kg
currently available. Mild overdosing should not
represent a major risk for an otherwise healthy
child >7.5 kg body weight (with an arbitrary
maximum dose of 20 µg/kg). Providing the parents
211

Food Allergy

with a syringe and a vial of epinephrine is an unsafe
and not easy-to-use alternative.17 On the other
hand, the 0.3 mg dose could be insufficient for
overweight individuals, who should have two
autoinjectors prescribed.
Devices should be stored at room temperature,
remote from heat sources and direct sunlight. They
have an average shelf-life of 1–2 year and should
therefore be re-prescribed accordingly. However, it
has been shown that epinephrine contained in
recently expired devices can still be effective and
used if no others are available.18

situation; the availability of two devices potentially
being recommended in case of:

Risks associated with self-injectable
epinephrine devices

It is controversial to recommend medications other
than self-injectable epinephrine, such as oral steroids and antihistamines, for the patient’s emergency kit, as they may delay the administration of
epinephrine in the absence of evidence of their
efficacy. However, a fast-acting antihistamine tablet
or drops to be administered for mild symptoms is
adequate for most patients, based on the recommendations of the written individualized treatment
plan (see below).

The pharmacological effect of an appropriate dose
of injected epinephrine includes side effects such as
pallor, palpitations and tremor. These usually last a
few minutes and remit spontaneously. Serious side
effects in otherwise healthy individuals are almost
always associated with overdosing. Inappropriate
use of the device – such as accidental injection into
a finger resulting in ischemia – can be prevented by
careful education.




remote access to medical care
body weight exceeding the maximum available
dose
• concerns about failure to respond to the first
dose
• any personal indicator suggesting an increased
risk.

Other medications available in the
emergency kit

Patient and family education
How many devices should a patient
be prescribed?
A second dose of epinephrine should be injected
within 5–10 minutes if the first one has not provided relief. It has been shown that up to 20% of
people experiencing anaphylaxis had to use more
than one dose of epinephrine.19 Most of the cases
were related to delayed or inappropriate administration; some children who needed more than one
dose of epinephrine had poorly controlled asthma.
However, few deaths have occurred after correct
treatment, which brings into question the systematic prescription of two devices. The economic
impact versus the potential prevention of fatalities
when two devices are prescribed remains unsolved.
Schools, nurseries and separated parents often
insist on being prescribed more than one device in
order to make self-injectable epinephrine available
at different locations. As an alternative to patients
carrying their medication, anaphylaxis emergency
kits could be readily stored and made accessible in
schools and nurseries – after proper training for
carers.16
In summary, the number of devices prescribed
will depend on a careful evaluation of the patient’s
212

Management of food allergies and their most severe
clinical expression, anaphylaxis, implies educating
and training patients, their families and, with regard
to children, their carers. At present there is still
in many countries a lack of adequate support for
allergic patients. Clark and Ewan,13,14 in a large prospective study of UK children with tree nut and
peanut allergies, have demonstrated that repeated
and thorough education reduces the severity and
frequency of reactions. Teaching should include
allergen avoidance, early identification of symptoms, and appropriate emergency treatment plans.
The ‘community’, i.e. schools and daycare, also
needs careful information on the medical condition of the allergic child and adequate emergency
management. Education is an ongoing process
and requires regular training, adapted to the age
and the psychosocial situation of the patient. It is
common for patients and their carers to forget
how and when to inject epinephrine, because reactions may be infrequent, they fear the needle, or
because of the side effects. Regular training sessions
are required to teach patients and their carers
how to treat reactions in a potentially stressful
situation.

Management of Food Allergy and Development of an Anaphylaxis Treatment Plan

CLINICAL CASE 2
A 6-year-old boy with a diagnosis of peanut allergy was on
holiday with his mother’s relatives. The family had taken
with them H1 antagonists but no self-injectable
epinephrine device. Epinephrine had not been prescribed,
as the child had had only a mild reaction after skin contact
with peanuts. He then ate a cereal snack which was
labeled as ‘could contain traces of peanut’. Ten minutes
after ingestion he developed mild angioedema, severe
difficulty breathing and loss of consciousness.
Intramuscular epinephrine was injected twice, with a
favorable outcome.

Discussion
This child was known for a mild systemic reaction related
only to peanut contact and subsequently developed a
severe reaction after ingestion of a very small amount.
Severe food allergy reactions may occur after previous
reactions without signs of severity, in particular in
peanut- or tree nut-allergic individuals. The prescription of
self-injectable epinephrine should be considered in
patients with nut allergies or reacting to small amounts of
a food. This child therefore had two distinct indications to
be prescribed epinephrine.
Food labeling should be included in the education plan of
all patients and their carers. This was highlighted in our
case by the fact that the child reacted after ingesting
traces of peanuts.
Food labeling varies between countries, with maximal
acceptable amounts of potential contamination by
allergenic foods usually clearly stated. However, the
regulations do not allow consumption of safe foods to
highly allergic individuals. In order to avoid the risk of legal
actions, the food industry increasingly labels products as
‘may contain …’, resulting in a reduced number of food
products available without “potential risk” to food-allergic
individuals.

A written individual management plan should be
given to both the patient and all their carers. These
have been shown to reduce the frequency and severity of further reactions. Adapted from the recommendations of the EAACI task force on the
management of children’s anaphylaxis,6 a written
individual treatment plan should list:



Personal identification data (name, address,
parents and doctor contact details, and, if
possible, a photograph)

Clear
identification of the allergens to be

avoided (including the different names used
for a food, for example arachis for peanuts)
• Treatment plan written clearly in simple nonmedical language with a stepwise approach:

15

• In case of breathing difficulty (wheezing,
chest whistling, throat tightness or voice
change) or collapse: give epinephrine
promptly (with the identified device and
dose)
• Call the emergency number (should be
identified)
• Recommendation to give a second dose of
epinephrine if no significant improvement
after 5–10 minutes
• First symptoms of allergy (swelling, redness
of the face, itching, nausea): give an
antihistamine
• Monitor the patient closely for signs of
breathing problems or collapse.
It is important to mention that relevant information for the food elimination diet and emergency
treatment must be easily available and readable
(see examples on www.foodallergy.org and www.
aaaai.com and Fig. 15.2).
The epinephrine autoinjector should be readily
accessible to every carer at all times.
Persons at risk for anaphylaxis in the community
may also wear or carry accurate and up-to-date
medical identification devices, such as bracelets or
wallet cards.

Involving the community in
management (Fig. 15.3)
The increasing prevalence of food allergy and anaphylaxis is a relatively recent phenomenon. Healthcare professionals are not all aware that anaphylaxis
occurs commonly in the community and are not all
able to recognize its signs and symptoms and to
treat them. Knowledge of the correct use of an
epinephrine autoinjector and teaching patients
how and when to use it is not always acquired.20
Health-care professionals should be prepared to
treat an acute anaphylaxis episode and also to
provide patients with accurate information on
potential symptoms, on the use of self-injectable
epinephrine and on food elimination diets.
The lay population, including teachers, is most
often not aware of the limitations on daily life for
a food-allergic patient. A major effort should be
made to improve risk awareness, as well as inte­
grating individuals with food allergy into a safe
community.
Management of food allergy in schools is a particular concern, as some surveys have shown that
213

Food Allergy

Figure 15.2  Example of written food allergy treatment plan.

214

Management of Food Allergy and Development of an Anaphylaxis Treatment Plan

15

Co-morbidities assessment
and treatment
• Asthma
• Cardiovascular diseases
• Mastocytosis, ...

Food allergens
avoidance
Long-term
risk
reduction

Immunomodulation

Emergency plan including:
• Self-injectable adrenaline
• Regular individual and
care-givers training
• Food allergy written
treatment plan

Community information
and education

Figure 15.3  Food allergy management in the community.

16–18% of children with food allergies experience
a reaction at school,21 sometimes as a first event.
School awareness of food allergy can be very diverse,
depending on national and regional regulations,
the presence of standardized food allergy management plans, or on previous food allergy reactions
in a given school. In France, despite the availability
of well-implemented and compulsory standardized
food allergy management plans, it could be shown
that nearly half of the children had no written food
allergy management plan and only 72% carried an
epinephrine autoinjector.22 In Australia, only 40%
of children known for a previous anaphylaxis reaction carried epinephrine with them and had an
anaphylaxis treatment plan implemented in their
school.23
Even if epinephrine is available at the school, it
is sometimes stored far away from the child – e.g.
in the school principal’s office or the nurse’s room.
As it has been shown that many deaths are linked
to late administration of epinephrine, the medication should be accessible within minutes. This
implies that epinephrine should be kept near the
child (for example stored by the teacher in the classroom) or directly carried by an older student.

These studies show the importance of implementing and reviewing food allergy management
plans at school, as well as the need for standardized
national and regional guidelines and regulations.
Teachers and other carers usually fail to recognize
signs of an allergic reaction, even in countries with
a higher level of awareness such as the USA. Sicherer
et al.,21 in a large study, recruited 4586 members of
the US Peanut and Tree Nut Allergy Registry, 16%
of whom reported reactions in school linked to
delayed or inadequate treatment.
Food elimination diets might be difficult to
implement in school, in particular in the catering
area. The goal should be to ensure a safe environment without social exclusion. In Europe, children
are most often provided with hot meals by a school
cafeteria or caterer, but special meals need to be
available for food-allergic children, or provided
from home. In schools with on-site restaurants, too
many children with food allergies are still excluded
from the school restaurant by the absence of trained
personnel, or because of fear of a reaction by the
parents or carers.
Many reactions in school may occur in classrooms – e.g. during craft projects – and not in the
215

Food Allergy

cafeteria,24 implying that foods should also be
avoided in the classrooms (see Clinical Case 3).

CLINICAL CASE 3
An 8-year-old girl, known for hazelnut allergy since she
was 3 years old (she initially presented with facial edema
after eating hazelnut chocolate spread for the first time),
was following a strict tree nut-elimination diet with yearly
reassessment of her allergies. She had a personalized food
allergy management plan (including a written anaphylaxis
treatment plan), and training for the use of epinephrine
autoinjectors was given to the family. She had also been
diagnosed with allergic asthma to dust mites and furred
pets, and was on daily treatment with inhaled steroids and
β2-agonists.
The food allergy management plan had been implemented
at school and kept in the principal’s office. However,
because of the girl’s young age and the fact that she was
taking her meals at home, the parents decided to keep the
autoinjector at home. A taste discovery week was organized
at school and all children were invited to taste blindfolded
different foods, including nuts. The girl did not want to
participate but was reassured by her teacher, who declared
that she would taste only healthy foods, such as fruits.
Within 10 minutes after eating one cashew nut, the child
developed facial edema and difficulty breathing, and lost
consciousness. The school nurse and the teacher called
her mother, who brought and injected the epinephrine.
A total of three injections were necessary to stabilize her
condition, followed by 24 hours’ surveillance in the
intensive care unit.

Discussion
This child was known for IgE-mediated tree nut allergy and
allergic asthma. These two conditions, which often coexist
in fatal anaphylaxis, require the compulsory prescription of
a self-injectable epinephrine device and a food allergy
management plan. Despite epinephrine having been
prescribed, it was not available at school, suggesting
insufficient patient/carer education:
• The parents kept epinephrine at home
• The school carers were not trained to recognize the
forbidden foods, or to treat allergic reactions.
Probably because of the delayed epinephrine
administration and the coexisting asthma, the girl’s
reaction was very severe and long-lasting.
This case report emphasizes the importance of educating
all carers about a specific allergic child, and of community
awareness of potential problems linked to food allergy.
Education should be regularly repeated – we suggest a
minimum of once a year – including regular training on
label reading, as well as recognition of allergic symptoms
and their appropriate treatment.

216

School or summer camps represent another
activity with an increased risk necessitating wellplanned organization and collaboration between
parents, teachers, cooks, dietitians and healthcare
professionals.
In the USA the Food Allergy and Anaphylaxis
Network (FAAN), a food allergy patient organization, provides useful materials for school professionals, such as information brochures, posters and
food allergy action plans. Together with the
National School Board Association, the National
Association of School Nurses and the National
Association of School Principals, FAAN has produced a document entitled School guidelines for
managing students with food allergies in order to
provide general principles applicable to the different States’ policies and education systems. A majority of American States have developed local food
allergy management policies, and the US Department of Agriculture has edited a guidance document about school lunches for special needs,
including severe food allergy, to ensure students
have safe substitute meals available.
In Japan, Guide-lines for the treatment of allergic
diseases in schools were published in 2008 by the
Japanese Society of School Health, including The
School Life Management Certificate, which was distributed to education boards nationwide. The availability of ‘safe foods’ in schools, recognition of
symptoms of food allergy and their treatment will
be implemented in the Japanese education system
in order to improve food allergy management.

Future perspectives
There are only a few evidence-based studies for
establishing guidelines on the management of food
allergy, and most rely on expert opinions. Welldesigned controlled trials are needed in order to
increase our understanding of the mechanisms of
action of the various treatments for food allergy
reactions.
The self-injectable epinephrine devices have fixed
doses which are not always suitable for specific conditions such as young age or overweight. Devices
with doses above 0.3 and below 0.15 mg should
soon be available (a device that injects 0.5 mg is
newly available in some countries).
Because of their fear of needles, individuals with
anaphylaxis are occasionally not adequatly treated

Management of Food Allergy and Development of an Anaphylaxis Treatment Plan

with epinephrine. Efforts must be made to educate
individuals and their families about the side effects
of epinephrine and indications for its use. However,
no alternative methods of administration are available, and more research is needed.
National guidelines on food allergy management
adapted to the local social environment should be
developed and implemented.
Standardized written national or regional management plans for food allergy should be
developed, and carers such as teachers and educators should be informed on an individual basis
about the basics of food elimination diets and the
recognition of food allergy symptoms and their
treatment.25 Politicians need to be alerted about the
increasing number of anaphylactic reactions in
the community in order to be able to adapt regulations and provide community funding for their
implementation.
Finally, food allergy has a high emotional impact
and affects the quality of life of both patients
and carers. This aspect is currently insufficiently
explored with regard to its professional and personal implications.

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the treatment of anaphylaxis: cochrane systematic
review. Allergy 2009;64:204–12.
3. Sicherer SH, Noone SA, Munoz-Furlong A. The impact
of childhood food allergy on quality of life. Ann
Allergy Asthma Immunol 2001;87:461–4.
4. Avery NJ, King RM, Knight S, et al. Assessment of
quality of life in children with peanut allergy. Pediatr
Allergy Immunol 2003;14:378–82.
5. Sampson HA. Anaphylaxis and emergency treatment.
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6. Muraro A, Roberts G, Clark A, et al. The management
of anaphylaxis in childhood: position paper of the
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CHAPTER

16 

Patient Education and Empowerment
Kim Mudd and Robert Wood

Introduction
Empowerment is a process that helps people gain
control over their own lives. Empowering foodallergic patients starts with education. Allergen
avoidance, symptom recognition and appropriate
treatment are the major educational needs to be
addressed. Empowerment evolves as individuals
acquire confidence in their knowledge and ability
to manage their food allergy and become
self-sufficient.

Avoidance
‘Allergen avoidance’ is a deceptively simple phrase
that encompasses everything from mastering Food
and Drug Administration food label laws to evaluating the effectiveness of food bans in public settings. Allergen avoidance begins with a strategy to
identify foods that contain food allergens through
label reading, identifying unexpected sources of
food allergens and cross-contamination, and avoiding certain types of contact with food allergens.

Label reading
Avoidance starts with label reading. It is a simple
concept until you consider the number of ingredient labels on foods, cosmetics, medications and pet
foods in the average grocery cart. People with food
allergies need to read every ingredient label, every
time, and never assume that products are ‘safe’
because changes can be made at any time. It is also
© 2012, Elsevier Inc

important to realize that different sizes of the same
food can have different ingredi