Effects of capsaicin desensitization on taste in humans.

The desensitization effects on taste resulting from application of 100 or 10 ppm capsaicin, accompanied by daily testing of a capsaicin series (1-1000 ppm, in log steps), or the desensitization resulting from application of 100 ppm capsaicin without the daily capsaicin testing, were investigated. The taste stimuli were three concentrations each of NaCl, sucrose, citric acid, quinine and 6-n-propylthiouracil. Following either type of 100 ppm desensitization, the magnitude estimates of the two bitter tastes, in particular, and citric acid showed significant decrements. Following 10 ppm capsaicin or an ethanol control procedure, there were no such effects. Recovery was complete in 1-3 days. It seems possible that the taste decrements are due to effects on both the taste and tactile components of taste, though there is a stronger case for effects on the tactile component.