Topical non-steroidal anti-inflammatory drugs inhibit non-immunologic immediate contact reactions

The effects of 3 topical applications of non-steroidal anti-inflammatory drugs (NSAIDs), diclofenac 1%, naproxene 10% and salicylic acid 5% in gel vehicles, on immediate contact reactions to 500 mM benzoic acid, 500 mM cinnamic aldehyde, 50 mM methyl nicotinate, all in pet., and 14.1 M (100%) dimethyl sulfoxide, were studied in 16 medical students. Erythema and edema reactions were observed visually, and the changes in the skin blood flow were monitored using laser-Doppler flowmetry (LDF). NSAIDs had significant inhibitory effects on erythema induced by all 4 substances tested and on edema induced by methyl nicotinate. The inhibition was probably due in part to percutaneous absorption and systemic effects of NSAIDs. There were differences between visual and LDF assessments, which stresses the importance of monitoring erythematous reactions of the skin both visually and with LDF.