Chapter 23: Food allergy.

The onset of IgE-mediated food allergy is usually within minutes to 2 hours of food ingestion. Risk factors for fatal food-induced anaphylaxis include presence of asthma (which is a risk factor for anaphylaxis in general), failure to use epinephrine autoinjectors promptly, history of prior severe reactions, known food allergy, denial of symptoms, and adolescent/young adult age. The most commonly implicated foods are cow's milk, eggs, peanuts, soy, tree nuts, fish, shellfish, and wheat. Allergies to peanut, tree nuts, and seafood are the most common food allergens in adults. The major food allergens are glycoproteins that are generally water soluble and stable to the effects of heat, proteases, and acids. Food proteins that escape proteolysis are taken up by intestinal epithelial cells and presented to primed T cells. This process leads to the generation of T-helper type 2 (Th2) cells that produce IL-4, IL-5, and IL-13. Recent studies have found that tolerance can be acquired with >70% of children becoming tolerant to cow's milk and eggs by age 16 years. Allergies to peanuts, tree nuts, and seafood are frequently lifelong. Food-allergic patients or their care givers should be taught when and how to administer injectable epinephrine. In terms of prevention, the American Academy of Pediatrics concluded that there is no convincing evidence that delaying the introduction of solid foods, including common allergens, beyond 4-6 months of age has a protective effect on the development of atopic disease.