[Diarrhea as manifestation of allergic diseases. The difficult search for the allergen].

Allergy is a very uncommon cause of diarrhoea. Other mechanisms, medical diseases and infections, psychological and pseudoallergic reactions, intolerance reactions, and enzyme defects/deficiency, and many other conditions are much more common. If food allergy is strongly suspected diagnosis may be difficult, even for allergologists, as it requires a mosaic of history, skin and in vitro tests, diagnostic diet, and even provocation tests. It is important to recognise diarrhoea "accompanying" allergic urticaria and anaphylactic reactions as part of the symptomatology of the primary dermatological or allergic disease and to refer the patient to the appropriate specialist.