Acetylsalicylic acid inhibits non-immunologic contact urticaria.

To investigate the mechanisms of non-immunologic contact urticaria (NICU), the effects of 1g + 1g of acetylsalicylic acid (ASA) on contact reactions to methyl nicotinate, diethyl fumarate, benzoic acid, cinnamic acid, cinnamic aldehyde and dimethyl sulfoxide were studied in 21 test subjects. Erythema and edema reactions were observed visually, and the changes in the skin blood flow were monitored using laser-Doppler flowmetry. ASA had a significant inhibitory effect on erythema from all 6 agents and also on edema from all substances except dimethyl sulfoxide. The mechanism of the effect may be a result of the inhibitory influence of ASA on prostaglandin bioformation. Thus, to avoid false negative test results, non-steroidal anti-inflammatory drugs should not be used during NICU tests.