Sensory characteristics of camphor

The perceptual effects of camphor on hairy skin were measured in a psychophysical experiment. Subjects rated the intensity and quality of sensations produced when a solution of 20% camphor (in a vehicle of ethanol and deionized H2O) was applied topically to the volar forearm. Under conditions in which skin temperature was varied either from 33-43 degrees C or from 33-18 degrees C, it was found that camphor increased the perceived intensity of the cutaneous sensations produced during heating and cooling. Although camphor's effect appeared to be greater during warming, neither effect was large. Camphor also produced a significant increase in the frequency of reports of "burning." It is concluded that camphor is a relatively weak sensory irritant that may have a modest excitatory effect on thermosensitive (and perhaps nociceptive) cutaneous fibers.