Inhibition of histamine skin flare reaction following repeated topical applications of capsaicin.

The intention was to clarify, experimentally, some of the clinical properties of capsaicin. The modulation of histamine-induced immediate inflammatory responses following subsequent topical applications of capsaicin was studied. A gradual dose-dependent reduction of the acute inflammatory reaction was observed after daily epicutaneous application of 1% capsaicin for 6 days. The modulation suggests that the small nerve fibres responsible for the neurogenic spread of the flare gradually become less excitable. After termination of capsaicin applications the flare returned to its initial value after 9 days. The recovery phase was longer than the inhibition phase, probably due to slow repletion of neuropeptides in the cutaneous nerve endings.