Food intolerance is not IgE-mediated but caused by histamine. A diminished histamine degradation based on a deficiency of diaminoxidase is suspected to be the reason. The therapeutic efficacy of a histamine-free diet was evaluated in 100 patients with food intolerance and allergic diseases, who were required to avoid fish, cheese, hardcured sausage, pickled cabbage, wine and beer for 4 weeks. Considerable improvement was observed in 57 patients, 15 of whom had total remission. The most striking treatment results were obtained in food or wine intolerance (80% P < 0.05; treatment of choice), bronchial asthma (80%), headache (64%) and urticaria (58%). After ingestion of food rich in histamine clearcut recurrence of atopic eczema was seen in 50% of the patients affected. Histamine plays a major part in food and wine intolerance. Histamine in food causes worsening of symptoms in atopics and patients suffering from headache. The results obtained indicate a deficiency of diaminoxidase in patients with intolerance to food or wine. Histamine levels in alcoholic beverages should be displayed on the labels.