Adverse reactions to foods and food additives include those that involve an immune mechanism of reaction (food allergies) and those that are non-immunological in nature (food intolerance). The signs and symptoms of food allergy usually involve the skin and gastrointestinal tract and are "classic" allergic symptoms. Food intolerance occurs more frequently at all ages. A number of food additives have been implicated in food intolerance, as none involve an immune mechanism of reaction. The role of food additives in food intolerance is not well established in many cases, has been discounted in others and continues to be the subject of current research. Although the history of events concerning an adverse reaction is important and gives clues to the specific type of problem (food allergy versus food intolerance), confirmation of the reaction is sometimes desirable. This can be done either by use of a standard elimination diet of non-allergic foods, followed by open challenge or by DBFC for more difficult situations. Food allergy skin testing and other in vitro immunologic tests may be helpful as supplemental information in those cases where food allergy is suspected. The best treatment for an adverse reaction to food is avoidance. Unproven and unapproved diagnostic (e.g., leukocytotoxic test) and therapeutic techniques (e.g., sublinqual neutralization) are not recommended in food allergy management.