Page 651 - Clinical Immunology_ Principles and Practice ( PDFDrive )

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Food Allergy

J. Andrew Bird, Stacie Jones, Wesley Burks

Adverse reactions to foods may be mediated by immunological soy (~0.4%), tree nuts (e.g., cashew and walnut) (0.2%), fish
mechanisms (food allergy) and nonimmunological mechanisms (0.1%), and shellfish (0.1%). Prevalent allergens vary in different
(food intolerance). Immune-mediated reactions to foods most cultural groups, with milk, egg, peanut, and tree nut allergens
commonly involve immunoglobulin E (IgE), an antibody that topping the lists in the Americas, Australia, and Western Europe,
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binds to mast cells and basophils. Upon exposure to allergen, whereas fish and shellfish allergies are more common in Asia.
they release inflammatory mediators, such as histamine, prost- Most food allergies are typically outgrown; however, allergies to
aglandins, and leukotrienes, resulting in symptoms ranging from some foods, such as peanut, tree nuts, fish, and shellfish, are
localized oral itching to anaphylaxis, a potentially fatal systemic often more persistent, and these are the food allergens most
reaction. Non–IgE-mediated immune reactions to foods include commonly reported in adults. Food allergy commonly co-occurs
such diseases as celiac disease and food protein–induced entero- with other atopic diseases, such as atopic dermatitis (AD), asthma,
colitis syndrome (FPIES), while other diseases, such as eosinophilic and allergic rhinitis. 5
esophagitis (EoE) and eosinophilic gastroenteritis (EGE), involve
both IgE-mediated and non–IgE-mediated mechanisms. Food SPECTRUM OF DISEASE
allergy has a significant negative effect on quality of life, and the
burden on the health system amounts to approximately $25 IgE-Mediated Food Allergies
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billion US dollars annually. Current management of food allergy Immediate reactions to foods compose the largest proportion
relies on avoidance, but ongoing research into treatment for of food-induced allergic diseases. IgE-mediated food allergy
food allergy should provide options for the majority of affected occurs when allergenic proteins cross-link allergen-specific IgE
persons in the near future. This chapter will review the basics bound to mast cells or basophils, leading to release of histamine
of food allergy diagnosis, management, and natural history, with and other inflammatory mediators. Symptoms of IgE-mediated
a specific focus on IgE-mediated food allergies. food allergy usually occur within minutes after ingestion of the
provoking food allergen, and do not start >2 hours later except
KEY CONCEPTS in very rare circumstances (e.g., delayed anaphylaxis related to
red meat ingestion).
Common Characteristics of Most Frequently Symptoms may be severe (e.g., anaphylaxis) or localized (e.g.,.
Encountered Food Allergens pollen-food allergy syndrome). Characteristic signs of an immedi-
ate allergic reaction manifest through skin and subcutaneous
A relatively small molecular weight (<70 kDa)
Abundant source of the relevant allergen tissues (e.g., urticaria and/or angioedema), the respiratory system
Glycosylation residues (e.g., bronchospasm), the gastrointestinal system (e.g., vomiting
Water solubility and/or diarrhea), and/or the cardiovascular system (e.g., increased
Most are resistant to heat and digestion vascular permeability leading to hypotension). Anaphylaxis is
the most severe symptom of food allergy and may result in death
(Chapter 42).
PREVALENCE Pollen-food allergy syndrome (PFAS, or oral allergy syndrome)
symptoms are restricted to the lips, throat, and mouth and are
The true prevalence of food allergy is difficult to establish. This most commonly elicited due to fruit and vegetable proteins
is probably because (i) studies have focused on only the most cross-reacting with antibodies against pollen proteins in individu-
common food allergens; (ii) the incidence and prevalence of als with pollen allergy. Affected individuals will typically complain
food allergy may be increasing and changing with time, with of pruritus and/or tingling of the lips, tongue, roof of the mouth,
studies showing an increasing prevalence over the past 10–20 and throat with or without swelling. PFAS reactions are unlikely
years; and (iii) studies of prevalence are difficult to compare to progress to a systemic reaction.
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because of inconsistencies and deficiencies in study design. Best More than 170 foods have been reported to be allergenic, but
estimates suggest a self-reported prevalence of food allergy of most of the food-induced allergic reactions are caused by eight
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12% and 13% for children and adults, respectively, with confirmed food groups. Cow’s milk, hen’s egg, and peanut are the most
food allergy in approximately 3% of adults and children when commonly identified food allergens in the United States, followed
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assessed by double-blind placebo-controlled food challenge. The by tree nuts, wheat, soy, fish, and crustacean shellfish. There is
most common foods to trigger reactions in children are cow’s variability across the world and cultural groups with regard to
milk (2.5%), hen’s egg (1.3%), peanut (0.8%), wheat (~0.4%), which allergens are the most common, but cows’ milk and hen’s
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