The effects of cooling and topical application of menthol on histamine
-induced itch, wheal and flare reactions of the left lower arm were in
vestigated in a threefold cross-over design with 15 healthy male volun
teers. Lowering skin temperature by cooling from 32.8 +/- 0.3 degrees
C to 29.7 +/- 0.5 degrees C reduced itch intensity from 260 +/- 47 uni
ts to 55 +/- 12 units (visual analogue scale) and flare diameters from
39.0 +/- 2.0 mm to 30.2 +/- 1.8 mm; wheal reactions were not affected
. A similar reduction in itch was found under menthol (42 +/- 14 units
) although skin temperature was not decreased. These findings suggest
a central inhibitory effect of cold sensitive A-delta fibre activation
on itch.