Menthol modulates oral sensations of warmth and cold.

Aqueous solutions of menthol were found to affect oral thermal sensation in the following ways: When menthol solutions were sipped and held in the mouth for 5 sec, solutions above oral temperature felt significantly warmer than deionized water of the same temperature (warmth enhancement). Menthol solutions below oral temperature felt cooler than water of the same temperature, but only slightly so (cold enhancement); Pretreating the mouth with 0.02% menthol for 5 min strengthened cold enhancement but attenuated sensations of warmth (warmth attenuation); Pretreating for 10 min produced continued cold enhancement while judgments of warmth returned to normal levels; L-menthol cooled more effectively than d-menthol, but d-menthol attenuated warmth at least as much as l-menthol. Possible explanations for the intermodal differences are discussed, and suggestions are made for future research into menthol's unexpectedly complex perceptual effects.