Adverse reactions to food may be mediated by immunological or non immunological mechanisms. The term "food allergy" describes an event in which a definite immunopathological process can be demonstrated and a cause and effect relationship must be present. Symptoms and signs of food allergy may appear in any organ system, depending in part on the age of the subject and on the allergen involved. At present it is generally agreed that the only effective therapy for food allergy is strict elimination of the offending food antigen. Institution of a food elimination diet should be considered comparable to prescribing a medication, which carries along definite risk-benefit ratio. Consequently, appropriate diagnostic measures base on history, skin test, or radioallergosorbent test (Rast) and blind food challenges, must be utilized before implementing special diets. The allergist and other health care professionals must recognize the advantages of elimination diets (improvement of symptoms) as well as disadvantages (increase of the time required to purchase food and prepare meals, impossibility to eat at restaurants, at friends' houses or at school with consequent possible social isolation, nutritional disorders) and choose the most appropriate elimination diet.