Food Allergy and Eosinophilic Gastroenteropathies

Food allergies are defined as an adverse immune response to food proteins. Food allergies may manifest as acute reactions, for example anaphylaxis, or they may contribute to chronic disease such as atopic dermatitis or eosinophilic gastroenteropathies. Significant food allergies affect as many as 6% of young children and 3-4% of adults and appear to be increasing in prevalence. Both IgE-mediated and non-IgE-mediated (cellular) mechanisms result in a spectrum of food-allergic disease affecting target organs such as the skin and the respiratory and gastrointestinal tracts. Food allergy results from an abrogation of normal oral tolerance, and the phenotypic manifestations are influenced by host factors such as target organ reactivity and the degree and type of immune response, and by features of food allergens, such as stability during heating or digestion. Almost any food may provoke a reaction, but relatively few foods are responsible for the majority of significant food allergic reactions: milk, egg, peanuts, tree nuts, fish, and shellfish. Disease manifestations of IgE-mediated reactions may include specific symptoms such as urticaria, angioedema, wheezing, vomiting, abdominal pain, and hypotension/shock. Disorders that are IgE antibody mediated include pollen-food related syndrome (oral pruritus from pollen-homologous proteins in raw fruits/vegetables), anaphylaxis, and food-associated exercise-induced anaphylaxis. Disorders that are cell-mediated and rarely associated with detection of food-specific IgE include infantile proctocolitis, enterocolitis and enteropathy. Several chronic disorders often responsive to elimination diets are variably associated with foodspecific IgE: eosinophilic esophagitis and gastroenteritis, and atopic dermatitis. Diagnosis requires a careful history followed by laboratory studies, elimination diets, and often physiciansupervised oral food challenges to confirm a diagnosis. Many food allergens have been characterized at a molecular level, which has increased understanding of the immunopathogenesis of food allergy and may soon lead to novel diagnostic and therapeutic approaches. However, current management requires educating the patient to avoid ingesting the responsible allergen and to initiate therapy, for example with injected epinephrine, in the event of unintended ingestion leading to anaphylaxis.