Perception of histamine-induced itch elicited in three different skin regions.

In order to investigate whether any regional difference in itch perception exists in experimentally induced pruritus, various concentrations of histamine (1, 3.3, 10, 33 and 100 micrograms/ml) were injected intradermally in three different skin regions in 15 healthy subjects. The regions were 1) the volar aspect of the forearm, 2) the lateral aspect of the upper arm and 3) the upper back at scapular level. Itch perception (itch latency, itch duration, maximal itch intensity, 'total itch index') and flare reactions were studied. A significant dose-response relationship was shown in each of the three regions for all itch variables, except itch latency, and for the flare reactions. However, no significant regional difference in itch perception was observed. The flare reaction showed a regional variation, with significantly smaller flares on the forearm than in the other two regions.