Capsaicin desensitization and stimulus-induced recovery on facial compared to lingual skin

It was recently demonstrated that capsaicin desensitization of the tongue can be temporarily reversed during bouts of recurrent or constant stimulation. The present study investigated whether this "stimulus-induced recovery" (SIR) also occurs on skin other than the oral mucosa. Twenty-two subjects received capsaicin treatments on the cheek and on the tongue tip at concentrations (330 and 33 microM) that produced approximately equal sensory irritation on the two sites. Desensitization and SIR occurred on both test sites, although the longer time course of irritation on the face changed the magnitude and form of SIR. There were large individual differences in the extent of desensitization and recovery, and the two phenomena were not correlated across sites, i.e., the capacity for SIR on the tongue was not a good predictor of an individual's capacity for SIR on the face. The results are discussed in terms of possible sources of regional and individual differences, and the implications they may have for the efficacy of topical analgesics that contain capsaicin.