IgE-Mediated Food Allergy

Food allergies are defined as adverse immune responses to food proteins that result in typical clinical symptoms involving the dermatologic, respiratory, gastrointestinal, cardiovascular, and/or neurologic systems. IgE-mediated food-allergic disease differs from non-IgE-mediated disease because the pathophysiology results from activation of the immune system, causing a T helper 2 response which results in IgE binding to F-c epsilon receptors on effector cells like mast cells and basophils. The activation of these cells causes release of histamine and other preformed mediators, and rapid symptom onset, in contrast with non-IgE-mediated food allergy which is more delayed in onset. The diagnosis of IgE-mediated food allergy requires a history of classic clinical symptoms and evidence of food-specific IgE by either skin-prick or serum-specific IgE testing. Symptoms of IgE-mediated food allergies range from mild to severe. The severity of symptoms is not predicted by the level of specific IgE or skin test wheal size, but the likelihood of symptom onset is directly related. Diagnosis is excluded when a patient can ingest the suspected food without clinical symptoms and may require an in-office oral food challenge if testing for food-specific IgE by serum or skin testing is negative or low. Anaphylaxis is the most severe form of the clinical manifestation of IgE-mediated food allergy, and injectable epinephrine is the first-line treatment. Management of food allergies requires strict avoidance measures, counseling of the family about constant vigilance, and prompt treatment of allergic reactions with emergency medications. Guidelines have changed recently to include early introduction of peanuts at 4-6 months of life. Early introduction is recommended to prevent the development of peanut allergy. Future treatments for IgE-mediated food allergy evaluated in clinical trials include epicutaneous, sublingual, and oral immunotherapy.