Increased urinary excretion of the histamine metabolite N tau-methylhistamine during acetylsalicylic acid provocation in chronic urticaria patients.

Seventeen chronic urticaria patients with a history suggestive of acetylsalicylic acid (ASA, Aspirin)-intolerance were challenged with ASA; only 2 patients showed marked clinical reactions. These clinical reactions were accompanied by a significant increase in the urinary excretion of the most important histamine metabolite, N tau-methylhistamine, in comparison with 15 non-responders (p less than or equal to 0.05) and placebo test. These results suggest an involvement of histamine in the pathogenesis of ASA-intolerance in chronic urticaria patients.