The term "food allergy" refers to adverse immunologic reactions to food. Food allergy is usually mediated by IgE antibody directed to specific food proteins, but other immunologic mechanisms can also play a role. The primary target organs for food allergic reactions are the skin, the gastrointestinal tract and the respiratory system. Both acute reactions (hives and anaphylaxis) and chronic disease (asthma, atopic dermatitis and gastrointestinal disorders) may be caused or exacerbated by food allergy. The foods most commonly causing these reactions in children are milk, egg, peanuts, soy, wheat, tree nuts, fish and shellfish; in adults, they are peanuts, tree nuts, shellfish and fish. The diagnosis of food allergy requires a careful search for possible causes, confirmation of the cause(s) with supporting tests, including specific tests for IgE (i.e., prick skin tests, radioallergosorbent tests) and, in some cases, oral food challenges. Treatment consists of elimination of the causal food(s) along with medical treatment, including the prompt self-administration of epinephrine in the event of a serious reaction.