Sensory irritation and coolness produced by menthol: evidence for selective desensitization of irritation

The temporal characteristics of the oral perception of menthol solutions were explored in two experiments. In Experiment 1, 10 samples of either 0.03% or 0.30% menthol were presented at 1 min intervals and rated for the perceived intensity of cooling and irritation. Reports of sensation quality (burning, tingling, stinging and numbing) and pain were also collected. At the higher concentration, a significant decrease in perceived intensity was observed over time for irritation, but not for cooling. Experiment 2 was designed to explore further the nature of the decline in irritation observed in Experiment 1. Employing 1-min and 5-min inter-stimulus intervals between solutions, it was found that the decrease in menthol irritation more closely resembled desensitization than adaptation. Decreases in the frequency of reports of the burning and stinging qualities, but not the tingling, numbing or cooling qualities, suggested that menthol has a specific desensitizing effect on a population of mucosal nociceptive fibers.