Oral allergy syndrome (OAS): symptoms of IgE-mediated hypersensitivity to foods.

Eighty highly atopic patients were selected for study because they had either atopic eczema (fifty cases) or atopic reactivity to foods, as judged by a positive skin-prick test (thirty cases). In all, sixty-five out of eighty subjects (81%) described symptoms of some kind provoked by foods, but correspondingly positive skin tests were found in only half of these, thirty-three out of eighty (41%). The symptoms experienced by thirty-one of the thirty-three patients with positive skin tests were immediate in onset (within 1 hr) and were at first confined to the upper gastrointestinal tract, the most frequent symptoms being oral irritation and throat tightness. In a proportion of these patients, further symptoms such as urticaria, asthma or anaphylaxis developed following the initial oral symptoms, which suggested the term 'oral allergy syndrome'. In the absence of the oral allergy, symptoms such as asthma, urticaria, migraine or eczema starting later than 1 hr after food were seldom associated with positive skin tests. In the oral allergy syndrome, the characteristic symptoms (strong association with positive skin tests and RAST, time of onset and sites at which symptoms are expressed) suggest a causative relationship between exposure to food antigens and specific IgE-induced release of mediators. In cases of food intolerance that lack a characteristic symptom pattern and a positive skin test or radio-allergo-sorbent test, it seems appropriate to consider non-IgE-mediated causes.