Dealing with Food Allergies in Babies and Children
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Dealing with Food Allergies in Babies and Children - Janice Vickerstaff Joneja
Copyright © 2007 Bull Pubishing Company
Bull Publishing Company
P.O. Box 1377
Boulder, CO 80306
(800) 676-2855
www.bullpub.com
ISBN: 978-1-933503-05-9
All rights reserved. No portion of this book may be reproduced in any form or by any means without written permission of the publisher. Manufactured in the United States of America.
Publisher: James Bull
Interior Design and Production: Shadow Canyon Graphics
Cover Design: Lightbourne Images
Library of Congress Cataloging-in-Publication Data
Joneja, Janice M. Vickerstaff, 1943-
Dealing with food allergies in babies and children / Janice Vickerstaff Joneja.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-933503-05-9
1. Food allergy in children—Popular works. 2. Food allergy in infants—
Popular works. I. Title
RJ386.5.J66 2007
618.92’975—dc22
2007023450
FIRST EDITION
10 9 8 7 6 5 4 3 2 1
Table of Contents
Title Page
Copyright Page
PREFACE
INTRODUCTION
Dedication
DISCLAIMER
CHAPTER 1 - What Is Food Allergy?
CHAPTER 2 - Dealing with Food Allergy in Babies and Children
CHAPTER 3 - Prevention of Food Allergy
CHAPTER 4 - Symptoms of Food Sensitivity in Babies and Children
CHAPTER 5 - Diagnosis of Food Allergy
CHAPTER 6 - Detecting Allergenic Foods: Elimination and Challenge
CHAPTER 7 - Milk Allergy
CHAPTER 8 - Lactose Intolerance
CHAPTER 9 - Egg Allergy
CHAPTER 10 - Peanut Allergy
CHAPTER 11 - Soy Protein Allergy
CHAPTER 12 - Allergy to Tree Nuts and Seeds
CHAPTER 13 - Wheat Allergy
CHAPTER 14 - Corn Allergy
CHAPTER 15 - Seafood Allergy
CHAPTER 16 - The Top Ten Allergens: Avoidance of Milk, Egg, Wheat, Corn, Peanuts, Soy, Tree Nuts, Seeds, Shellfish, and Fish
CHAPTER 17 - Fructose Intolerance
CHAPTER 18 - Anaphylaxis and Food Allergy
CHAPTER 19 - Hyperactivity and Diet
CHAPTER 20 - Autism and Diet
CHAPTER 21 - Oral Allergy Syndrome
CHAPTER 22 - Eczema and Diet
CHAPTER 23 - Asthma and Food Allergy
CHAPTER 24 - Immunologically Mediated Adverse Reactions to Foods in Childhood: Food Allergy, Food Intolerance, or Something Else?
CHAPTER 25 - Probiotics and Allergy
APPENDIX A - Dietary Considerations for the Expectant Mother
APPENDIX B - Gluten- and Casein-free Diet
APPENDIX C - Gluten-Free Diet for Management of Celiac Disease
APPENDIX D - Challenge Phase: Elimination and Challenge Protocols for Determining the Allergenic Foods
APPENDIX E - Maintenance Diets
APPENDIX F - A Useful Tool in the Dietary Management of Food Allergies
APPENDIX G - Vitamin B12
APPENDIX H - Sulfite Sensitivity
GLOSSARY
PREFACE
Some years ago I was invited to give a lecture at a conference organized by a food allergy support group in Ontario, Canada. As I made my way to the lecture theatre, I was confronted by a distressingly macabre scene: emergency health professionals in full uniform with ambulance stretchers and hospital gurneys and displays of resuscitation equipment complete with face masks, IV tubing, oxygen cylinders, and syringes ready for injections. Of course, such a scenario is not unusual when a patient is at risk of anaphylactic shock. However, as an exhibit, the message was too stark and frightening for a conference on food allergy in children.
Unfortunately, the exhibit set the tone for the whole meeting. Hair-raising stories of fatal and near-fatal anaphylactic reactions, frantic emergency calls, and terrifying races to the hospital by car and ambulance were recounted with relish. The attendees were, for the most part, parents whose children had been diagnosed with food allergy. Those new to the allergy scene were clearly distressed and upset. It is always important for anyone associated with food allergy, especially parents and care-givers of atopic infants and children, to be aware of all the potential dangers. But, to present the rare threat of anaphylaxis in such frightening and uncompromising terms amounts to quite unnecessary fear-mongering. Anaphylactic resuscitation is rarely required in the day-to-day management of food allergy. To generate such fear and anxiety at the outset of a conference designed to equip parents to handle food allergy in their children has the potential to jeopardize the well-being of not only the atopic child but also the whole family and the family’s support network. A story from my years as head of the Allergy Nutrition Program at Vancouver Hospital and Health Sciences Centre in British Columbia illustrates this well.
Jasona was a 14-year-old boy. He was referred to the Allergy Nutrition Clinic by his family doctor who was becoming concerned about his growth and development. Jason was an only child and came into the Clinic with his mother and father. His mother was a nurse and his father worked in retail sales. Jason appeared much smaller than would be expected for his age even though both parents were of normal height and stature. He was pale and fragile-looking and wore a baseball cap that hid his thin, sparse hair. His mother told his story.
Jason had been a colicky baby and had developed eczema at about two months of age. At six months his mother had consulted an allergist who performed skin tests for food allergy. The parents were informed that the skin tests were positive to everything.
A list of foods that Jason must avoid was provided by the allergist. Faithfully, the mother had eliminated all of the allergy foods,
and Jason had never eaten any of them. His diet consisted of about eight foods that were not on the allergist’s avoid list.
Jason had consumed only these foods since the age of six months. He had been given no nutritional supplements because his mother did not think they were safe.
Jason added his own story. He felt very unhappy in school. He was teased by the other children because of his sparse hair and his small size, which was more typical of a 9-year-old than a boy in his early teens. Jason’s father said little throughout the interview but made it clear that he felt his wife was overprotective
of the child. Nevertheless, he thought that because his wife was a nurse she was entitled by her training to be in charge of Jason’s health. The father was obviously unhappy about his child’s situation but felt powerless to intervene in any way.
It was clear to me that Jason needed to start eating a much wider range of foods than he was presently consuming. His small size, fragile appearance, and obvious lack of development were unmistakable indicators that multiple nutritional deficiencies were very real risk factors for his health and well-being.
We arranged for Jason to undergo challenge tests, starting with small amounts of individual foods and monitoring his reactions in a safe environment. I waited to hear the outcome, hoping for some encouraging news about his progress. Two weeks later, Jason and his mother came into the office; both were noticeably ill-at-ease. Apparently, the challenge test had been cancelled. No new foods had been introduced. Gradually, the sad story unfolded. Prior to the day scheduled for the first trial, Jason became extremely anxious and upset. He had become nauseated, vomited continuously, and was unable to sleep. Apparently, he was convinced that he was going to die as a result of eating the bad foods
and was so frightened that it would have been impossible for him to proceed with the food challenge test plan.
The father refused to take any further part in the process. He disagreed with his wife’s handling of Jason’s diet and felt she was over-protective of the boy to the point of obsession. The father had felt optimistic about the original plan for introducing new foods into the boy’s diet but was defeated when he was again faced with the fears of his wife and son. The father was distressed by the outcome of the proposed management strategy. He later left the family and the parents subsequently divorced.
These two scenarios represent extreme examples of the fears and stresses that a diagnosis of food allergy can impose on individuals and families. But the stories are representative of the anxiety and uncertainties that people experience when faced with the challenge of managing food allergies, especially in the infants and children who are so utterly dependent on them for their well-being and survival. Sometimes the responsibility seems overwhelming. When presented in such graphic terms as the first example, food allergy appears to be a loaded gun, primed and ready to end the life of an innocent child. However, a loaded gun has to be aimed and fired in order to pose a threat and even the family car can be an instrument of destruction. So, let us be realistic as well as responsible. Be careful—not fearful—and all will be well.
My message to those caring for an allergic child is simple. A diagnosis of food allergy is not a sentence of death; it is merely a signal that special caution and knowledge is required in the feeding of the precious life that has been entrusted to your care. This book has been written to provide the knowledge you need to care for you child with food allergies.
INTRODUCTION
A baby with food allergies is clearly suffering and the baby’s distress frequently persists despite the best efforts of parents and care-givers to provide relief. This so often leads to enormous stress for everyone involved, especially for first-time parents who are not only faced with the challenges associated with adjusting to this seemingly fragile and needy little person who is completely dependent on their care but who also have to cope with demands over and above the expected nourish, clean, and cuddle that satisfies most babies (or so they are led to believe!).
Sleepless nights and the inability to console a new baby cause a great deal of stress for everyone. Studies on infants with colic, which may often accompany food allergy, show that their mothers tend to be more concerned about their infants’ temperament, and even to feel rejection, compared with mothers with infants without colic.¹ Even more distressing is the finding that mothers seem to be less responsive to and interact less with infants they feel are difficult
at 3 months old. Strong negative emotions are still evident when these infants are 8 months old. Further, the associated feelings of guilt and inadequacy may last long after the child’s infancy.
If the baby with food allergy can be recognized early, there is a great deal that parents and care-givers can do to relieve the baby’s distress. These steps often completely avoid the negative consequences of failing to console a suffering infant. I have lost count of the number of mothers who have passed through my practice who have expressed their immeasurable happiness when, after recognizing and avoiding the offending foods, they are rewarded with a calm and contented baby. These mothers battled with a screaming tyrant
(their words) for far too long. Observing their obvious joy in bonding with their happy baby is a gift that I cherish every time I see it happen.
Food allergy in older children can cause even greater distress both for the child and their family. The child who is ostracized by his or her peers as a result of the unsightly skin of eczema is at risk of emotional scars that can persist long after the discomfort of the condition has been outgrown. A child who is unable to sleep as a result of the pain and distress of the symptoms of food allergy is often unable to function well during the day; they may suffer the consequences of poor school performance and related behavioral problems. An inability to join in childhood activities may cause distancing from peers, with the result that the allergic child’s social interactions are impaired for many years. The well-meaning family members who are doing their best to protect a potentially anaphylactic child from exposure to their food allergens can unwittingly compound the problems of social isolation, adding unnecessary fear and uncertainty on top of the burden of coping with the stressful symptoms of food allergy.
Some interesting studies, using health-related quality of life (HRQL) evaluation questionnaires, have revealed surprising information. Contrary to the prevailing assumptions, it is the fear of allergic reactions and the measures taken to avoid them, rather than the symptoms of allergy, that cause the greatest distress among food-allergic children and their families. In one study, more than half (55 percent) of the children had not experienced any food reactions in the past 12 months. Still, all the children were reported to have lower psychosocial HRQL than the general population.²
It is very important for you to realize that most of these negative consequences can be reduced—or completely avoided—with knowledge, understanding, and the careful management of your child’s food intake.
FOOD ALLERGY IN CHILDHOOD
Childhood is the period of life when allergies to food are most prevalent. Food allergy is much more common in babies and young children than in adults. Most food allergies are outgrown by the age of five years. Food allergy in adults is relatively uncommon. Estimates of food allergy in adults indicate an incidence of less than 2 percent. However, intolerance of food components, naturally occurring chemicals, and food additives is a frequent experience, and some practitioners estimate the incidence of these conditions as high as 50 percent of the adult population. Food allergy is a response of the immune system; a food intolerance can be broadly defined as a sensitivity mechanism that does not involve the immune system. Food intolerance is usually due to a physiological reaction such as an enzyme deficiency. We shall talk about the differences between food allergy and food intolerance later in this book.
Incidence of Food Allergy in Childhood
It is difficult to determine exactly how many babies and children are sensitive to foods and suffer symptoms as a result of eating or drinking. There is no single reliable laboratory test that can prove that a child is allergic or intolerant to a specific food or food additive. This makes estimating how frequently such reactions occur very difficult. Because there are so many different immunological and nonimmunological reactions involved in food sensitivity symptoms, it would be unrealistic to expect that a laboratory test alone could identify them all. In the end, the only accurate way to determine a child’s reactivity to a food, drink, or food additive is elimination and challenge, and this process is too expensive and time-consuming to be a routine procedure.
However, based on the statistics that are available, it is usually estimated that food allergy occurs in up to 8 percent of children under the age of five years, and that 2 percent of children in this age group have an allergic reaction to cow’s milk proteins. Based on specific studies, 4 to 6 percent of children had documented food allergy.³ The overall incidence of cow’s milk allergy ranged from 1.9 to 7.5 percent in different populations.⁴ Other reports suggest the incidence of food allergy in childhood to be up to 8 percent and food-related complaints
to afflict as many as 28 percent of children.⁵
An Australian study⁶ indicated that at the age of two years, egg was the most frequent food allergen (3.2 percent), while cow’s milk (2.0 percent) and peanut (1.9 percent) were fairly equal in frequency. Allergy to wheat, soy, sesame seed, cashew nuts, hazelnuts, and walnuts was less frequent and about equal in prevalence. Allergies to fish, Brazil nuts, and shell fish were quite uncommon. In Asian countries the reported frequency was remarkably similar to that in Australia, except allergy to seafood was more common than for nuts, peanuts, and wheat, if seafoods were a regular part of the infant’s diet. Rice hypersensitivity was rare in Australia and in Asian countries.
Progress of Food Allergy in Children
Early infancy is a particularly critical time because the baby might be at maximum risk of being sensitized to allergens. From birth to about two years of age, the baby’s immune system is relatively immature and the layer of cells lining the digestive tract (known as the gastrointestinal epithelium) may be more permeable than in the mature human. From the age of two years onward, children appear to outgrow their early food allergies. Based on research in animals, it is thought that tolerance to foods develops as the immune system matures and the lining of the digestive tract changes so that food molecules of the size required for an allergic reaction to occur cannot pass through the digestive tract tissues (the epithelium becomes less permeable).
Many experts believe that if a baby can be protected from becoming sensitized to the most highly allergenic foods when the immune system and the digestive tract are in the most vulnerable stage for allergy to develop, the incidence of lifelong food allergy and potentially life-threatening anaphylactic reactions to foods will be reduced and hopefully entirely prevented. When a baby has been identified to be at risk for developing allergy, measures to reduce allergic sensitization might be implemented at birth and the problems associated with future food allergy may be significantly reduced. However, as we shall see in later discussions, experts disagree on the best way to avoid this early allergic sensitization.
Nutrition for the Allergic Child
The most important aspect of managing food allergy in babies and children is to be sure that the developing child has each and every nutrient that is essential for its optimum growth and development. Deficiency in a critical nutrient in the early days can have enormous negative consequences that can, in some instances, last a lifetime. The words of a British group of practitioners eloquently express this most important aspect of infant feeding:
Few other aspects of food supply and metabolism are of greater biological importance than the feeding of mothers during pregnancy and lactation, and of their infants and young children. Nutritional factors during early development not only have short-term effects on growth, body composition and body functions but also exert long-term effects on health, disease and mortality risks in adulthood, as well as development of neural functions and behavior, a phenomenon called
metabolic programming.’"⁷
In the diligent search for and avoidance of the foods that cause the distressing symptoms of allergy, no one must forget that every nutrient that is eliminated as a result of its being part of allergenic food must be replaced by an equal amount of the nutrient from an alternative source. Information about the nutrients that may be deficient when some important foods are eliminated and the sources of these nutrients in alternative foods is provided in Appendix E.
The management of an allergic child’s diet is not achieved without some effort. It takes time, knowledge, and skill. However, all these things can be learned; it is truly not a demanding process. Once you have understood the underlying concepts of food allergy management, you will be surprised how easy and gratifying it can be to provide a safe, healthy, and enjoyable eating plan for your child and the whole family.
Foods That Cause Food Sensitivity Reactions
In theory, any food is able to trigger an allergic reaction. All foods contain molecules capable of triggering a response of the immune system. However, for many reasons—including both the structure of the food molecules and a child’s immunological responses—the foods that cause the majority of allergic reactions tend to be few in number.
Although people often look for the ideal hypoallergenic diet,
and often hear about the latest allergy diet
from popular publications and zealous friends, such a thing does not exist. What is hypoallergenic
for one child could be life-threatening for another. Each person is an individual. Inherited tendencies, medical history, family lifestyle, and response to both food and nonfood factors (such as airborne and environmental allergens) will all contribute to the way in which one child’s body reacts to the foreign
foods and chemicals that enter it.
There is no reason that any baby, child, or family should suffer as a consequence of food allergy. However, the management of the condition does require understanding and patience. This book provides information and guidelines that can help you meet the challenge of providing relief for both you and your allergic child.
References
1
Rogovik AL, Goldman RD. Treating infants’ colic. Canadian Family Physician 2005; 51(9):1209–1211.
2
Marklund B, Ahlstedt S, Nordstrom G. Health-related quality of life in food hypersensitive schoolchildren and their families: parents’ perceptions. Health and Quality of Life Outcomes 2006; 4:48.
3
Zeigler RS. Food allergen avoidance in the prevention of food allergy in infants and children. Pediatrics 2003; 111:1662–1671.
4
Jarvinen KM, Suomalainen H. Development of cow’s milk allergy in breast-fed infants. Clinical and Experimental Allergy 2001; 31:978–987.
5
Bock SA. Prospective appraisal of complaints of adverse reactions to foods in children during the first 3 years of life. Pediatrics 1987; 79:683.
6
Hill DJ, Hosking CS, Ahie CY, Leung R, Baratwidjaja K, Iikura Y, Iyngkaran N, Gonzalez-Andaya A, Wah LB, Hsieh KH. The frequency of food allergy in Australia and Asia. Environmental Toxicology and Pharmacology 1997; 4(1–2):101–110.
7
Koletko B, Agget PJ, Bindels JG, Bung P, Ferre P, Gil A, Lentz MJ, Robefroid M, Strobel S. Growth, development and differentiation: a functional science approach. British Journal of Nutrition 1998; 80(Suppl 1):S6–S45.
Dedicated to my own children, Sunil and Nalini, with whom I learned so much about food allergies, and who continue to inspire me to look further and search deeper for answers.
I also dedicate this book to all parents and care-givers of allergic babies and children.
DISCLAIMER
The information provided here is as up-to-date, accurate, and as practical as possible in a field that is moving very quickly and is full of controversy. However, we cannot guarantee or warrant the quality, accuracy, completeness, timeliness, appropriateness or suitability of the information provided. This book is not intended to provide specific medical advice, but rather is intended to provide users with information to better understand their health. You should not use the content of this book for diagnosing or treating a medical or health condition, and reliance on the content of this book is solely at your own risk.
Any information and advice in this book is not meant to take the place of that provided by a medical practitioner. If you have or suspect that you may have a medical problem, you should contact your professional healthcare provider. Any strategies suggested in this book should be discussed with and managed by a suitably qualified physician, and implementation should be supervised by a registered dietitian/nutritionist for maximum benefit. Never disregard medical advice or avoid seeking it because of something that you have read in this book.
The author and publisher disclaim any responsibility for any adverse consequences resulting from the use of drugs, foods, diets, or procedures mentioned in this book.
Food lists are never exhaustive. There will always be omissions and modifications. Manufactured products and their ingredients are constantly changing. Those listed in this book. although current at the time of publication, may not be up-to-date when accessed by the consumer. The reader should apply to the manufacturer to confirm all such listings.
Trade names of foods, drugs, medical devices, and other products are used only as examples. The trade names given are not meant as a complete list of those available or as recommendations of any particular product(s).
CHAPTER 1
What Is Food Allergy?
THE SIMPLE EXPLANATION
A simple explanation of food allergy is that it is an inappropriate response by the immune system that results in symptoms. Our immune systems keep us free from disease by recognizing a foreign invader
when it enters the body and by releasing in response a battery of defensive chemicals (called inflammatory mediators
) into local tissues and into the circulatory system. All the food we eat comes from foreign sources—plants and animals—that we consume as nourishment. Normally our immune systems see this material as foreign but safe
due to a complex process of tolerance that occurs when food is processed through the digestive system. When something goes wrong during this processing, a person becomes sensitized
to the food, and thereafter the immune system perceives it as foreign and a threat. Whenever that food enters the body again, the immune system treats it as if it could cause disease. The symptoms that we experience as a result of this defensive action are called allergy.
Unlike allergy, food intolerance does not involve a response of the immune system. The chemicals released in the immune response are not involved in an intolerance reaction. Most intolerance reactions that we understand (and there are many that we do not!) involve a defect in the processing of the food, either during digestion, or later, after the food parts, or components, have been absorbed into the body. The symptoms of food intolerance are often caused by an excess of a component that has not been digested completely (for example, lactose intolerance) or a component that, for some reason, cannot be processed efficiently after it has entered the body.
Whatever the mechanism that causes the symptoms, in the final analysis the only way to avoid distress is to avoid the foods that trigger the response. The first stage in avoidance, of course, is the correct identification of the foods and food components that are the triggers for the adverse reactions.
These are the simple bare bones
explanations for the ways in which our bodies react to foods when we experience food allergies or intolerances. However, these processes are complex and diverse. If you want a more detailed, scientific explanation of the mechanisms leading to food allergy and food intolerance, please read on.
This chapter explains food allergy; the rest of the book discusses how this knowledge applies to your child. Understanding these processes will take some time and effort for the nonscientist,
but it will ultimately be worthwhile. You will not only understand and appreciate how your child’s body functions when he or she is experiencing the distressing symptoms of an allergic reaction, but you will also understand what you can do, with the help of your pediatrician, dietitian, and other health care providers, to prevent or alleviate these symptoms at various stages in your child’s development. Furthermore, this chapter will help you to understand and evaluate information on allergy that you find in other sources.
THE BASICS OF ALLERGY
The symptoms of an allergic reaction are caused by biologically active chemicals produced by the immune system in its attempt to protect the body from a foreign invader. Our immune systems are designed to protect us from anything that might cause disease. Usually this is a microorganism such as a virus, bacterium, or other pathogen. However, the immune system of an allergic (atopic) person attempts to protect the body not only from potential pathogens but also from harmless substances such as pollens, animal dander, dust mites, mold spores, and food.
What is it that causes the immune system of one individual to fight a harmless substance, while another’s system recognizes the same materials as innocuous? Although we do not know the entire answer to this question, research is starting to reveal parts of the puzzle. The difference lies right at the beginning of the process of recognition of what is safe and what may be harmful to the body.
First, it is important for you to understand that food itself is incapable of causing any disease in the way that viruses, bacteria, and cancer cells can. There are no bad foods
! It is the body’s response to components of the food that results in the miserable symptoms we call food allergy, food intolerance, food sensitivity, or adverse reactions to foods. The reason that one child’s body responds to food by developing distressing symptoms, and that another’s uses the same food for comfort and nurture, may be found in several factors:
The child’s inherited genetic makeup
The circumstances under which the child first encountered the food
The microorganisms that live within a child’s digestive tract
The medications the child may have taken by mouth or been exposed to, for example, in mother’s breast milk
Other factors that we are only just beginning to (often incompletely) understand
Food sensitivity is unlike any other disease entity. It has many different causes, since any food is capable of triggering an allergic reaction in a child who has been sensitized to it, or who lacks the systems required to process it adequately when it enters the body. The same food may be absolutely safe for other children. Furthermore, food allergy can result in many different symptoms in diverse organ systems. For example, one child may develop symptoms in the skin, such as eczema or hives; another may have symptoms in the digestive tract, such as stomachache, diarrhea, nausea, or vomiting; yet another develops symptoms in the lungs, such as asthma; or the upper respiratory tract, with a stuffy, runny nose; or earache; or all body systems at the same time (anaphylaxis). All this may occur as a result of eating the same food, such as peanuts or shellfish for example. Each allergic child differs in the way his or her immune system responds to food and which foods it responds to.
The usual medical model of disease that your doctor traditionally follows has several distinct steps that lead from symptoms to therapy:
The symptoms (presentation
) suggest several possibilities as to their cause.
Tests are carried out that will lead to a diagnosis.
The diagnosis arrived at as a result of the tests determines the treatment.
Treatment usually consists of medications and/or surgery.
As a result of treatment (therapy) the symptoms are alleviated.
This protocol works extremely well for conditions that are caused by a single entity such as a bacterium, virus, cancer, injury, or other agents that cause harm to the body. It does not work well for food allergy, where there are many different agents responsible for triggering a response of the immune system, which results in a diverse array of symptoms that differ from person to person, and even within the same person at different times.
What this means in practice is that, because there are a number of different processes that can occur when body systems deal with the diverse chemicals that make up a food, it would be unrealistic to expect that the specific food responsible for triggering the body’s adverse reaction could be identified by any single laboratory test. Consequently, even a clear definition of the term food allergy
using symptoms, causative factors, physiological processes, or diagnostic tests (which are the usual ways we define a disease) has always eluded clinicians and scientists.
In the popular literature it has become convenient for all adverse reactions that result from eating to be labeled food allergy,
but in medical and scientific fields, there are several defined conditions within this broad category that indicate the probable mechanism of the reaction that is taking place within the body. These defined conditions help in determining the possible cause of the symptoms, predicting the probable severity and duration of the reaction, and suggesting the most appropriate treatment.
Definition of Food Allergy Terms
It will be helpful for you to have some understanding of the terms that are currently being used by practitioners in the field of allergy so that you can understand the medical literature as you search for information on your child’s allergy. Understanding the terms will also pave the way for our discussion of why your child has allergies and what is happening in his or her body when an allergic reaction is occurring.
The most recent attempt at a definition of adverse reactions to foods from the European Academy of Allergy and Clinical Immunology in 2001¹ includes the following:
Allergy is a hypersensitivity reaction initiated by immunologic mechanisms.
An adverse reaction to food should be called food hypersensitivity.
– When immunologic mechanisms have been demonstrated, the appropriate term is food allergy.
– If the role of IgE is highlighted, the correct term is IgE-mediated food allergy. [We shall discuss IgE and other antibodies later in this chapter.]
– All other reactions, previously sometimes referred to as food intolerance,
should be referred to as nonallergic food hypersensitivity.
Severe, generalized allergic reactions to food can be classified as anaphylaxis.
Anaphylaxis is a severe, life-threatening, generalized or systemic hypersensitivity reaction.
Atopy is a personal or familial tendency to produce IgE antibodies in response to low doses of allergens, usually proteins, and to develop typical symptoms such as asthma, hay fever (rhiniconjunctivitis) or eczema/dermatitis.
Previously, the American Academy of Allergy and Clinical Immunology (AAACI) and the National Institute of Allergy and Infectious Disease (National Institutes of Health (NIH))² defined the diverse terms in use thus:
An adverse food reaction is a generic term referring to any untoward reaction after the ingestion of a food.
Adverse food reactions can be
– Food allergy.
– Food intolerance.
A food allergy is the result of an abnormal immunologic response after ingestion of a food.
A food intolerance is the result of nonimmunological mechanisms.
In spite of (or more likely, because of) these seemingly precise, but sometimes conflicting academic definitions, authors of research papers and articles on food allergy now frequently define their own use of the terms in any published work so that the reader is quite clear about their meaning in that specific context. In accordance with this sensible practice, I will do likewise (see Table 1-1). I have used the 1984 definition of the AAACI/NIH in all my previous publications and still find this the least confusing; I will continue that practice here. The terms anaphylaxis and atopy I use in the way they are defined by the EAACI.
Table 1-1
DEFINITION OF TERMS AS USED IN THIS BOOK
Now that you understand what each of the terms means, we can go on to discuss the subject much more easily. If you want to refresh your memory until the terminology becomes quite familiar to you, please look at the Glossary (pp. XXX–YYY). We can start with a discussion of what happens in the body when an allergic reaction takes place.
The Immunological Process in an Allergic Reaction
When an allergen enters the body of a person at risk for allergy, an extremely complex series of events is set in motion that will finally result in the release of chemicals (called inflammatory mediators) that act on body tissues to cause the symptoms of allergy. All immunological processes involve the various white blood cells (leukocytes), and the different types of chemicals they produce. For a more detailed description of the immunological process of allergy, you may wish to read Chapter 3 in the companion book in this series.³
The first stage of the immunological response involves recognition of the invading antigen. An antigen is a protein within the cells of any living (or previously living) material that enters the body causing the immune system to react to it. All foods contain numerous antigens. When the antigen causes an immune response that results in allergy, we call it an allergen. Not all foreign proteins (antigens) cause allergy, and therefore not all antigens are allergens. On the other hand, all allergens are antigens.
When an antigen enters the body, the white blood cells called lymphocytes are activated. Lymphocytes are the first cells of the immune system that recognize and respond to anything foreign entering the body. We can visualize them as the sentinels of the immune system. There are two different types of lymphocytes in blood: T cells and B cells. T-cell lymphocytes are the ultimate gatekeepers
and controllers of the immune system. We will discuss B cells later in this chapter.
T-cell Lymphocytes Detect a Foreign Invader
Certain types of T cells, called helper T cells (Th cells), are responsible for identifying foreign materials that enter the body through any route, such as the mouth, nose, and skin. Th cells initiate and direct the subsequent activities of the immune system if the foreign material is deemed a threat to the health of the body. T cells exert their control of the whole immune response by means of a number of different types of messenger chemicals
called cytokines. The responses of helper T cells in allergic and nonallergic individuals are different. The two types of responses have been designated Th2 and Th1 response, respectively (see Figure 1-1). Different cytokines are released in each response, and they control the way in which the body reacts to the foreign material.
Figure 1-1
Cytokines Direct the Immune Response
When a pathogen (disease-causing microorganism) enters, the immune system protects the body by a Th1