Adverse reactions to foods, aside from those considered toxic, are caused by a particular individual intolerance towards commonly tolerated foods. Intolerance derived from an immunological mechanism is referred to as Food Allergy, the non-immunological form is called Food Intolerance. IgE-mediated food allergy is the most common and dangerous type of adverse food reaction. It is initiated by an impairment of normal Oral Tolerance to food in predisposed individuals (atopic). Food allergy produces respiratory, gastrointestinal, cutaneous and cardiovascular symptoms but often generalized, life-threatening symptoms manifest at a rapid rate-anaphylactic shock. Diagnosis is made using medical history and cutaneous and serological tests but to obtain final confirmation a Double Blind Controlled Food Challenge must be performed. Food intolerances are principally caused by enzymatic defects in the digestive system, as is the case with lactose intolerance, but may also result from pharmacological effects of vasoactive amines present in foods (e.g. Histamine). Prevention and treatment are based on the avoidance of the culprit food.