SCRATCHING AND ULTRAVIOLET-IRRADIATION - AN EXPERIMENTAL ANIMAL-MODEL

The purpose of the study was to establish a useful animal model for qu antification of itching and to examine whether the wavelengths inducin g itching were identical to those inducing erythema. Four groups of ha irless mice were irradiated with 4 different light sources in order to provoke itch. The light sources were adjusted to give equal erythroge nic doses. The groups were treated 5 times weekly for a year. For the first 16 weeks the daily dose was 0.6 minimal erythema dose (MED) and for the following 36 weeks 1.2 MED. The severity of the itching in the 4 groups and in a control group of untreated mice was compared. The c hosen parameters were the number of scratch-sequences and the summariz ed time of scratching during an observation period of 1 h. Ultraviolet irradiation provoked itching. Especially the wavelengths 315 330 nm w ere more itch-provoking than erythemogenic. The difference between the control group and a group treated with Philips TL12 combined with a T empax filter was significant. An action spectrum of itching does not s eem to be identical to the erythema action spectrum. The animal model described is usable to quantify itch but has to be simplified. Of the lamps used. Philips TL01 was the least itch-provoking lamp type and ma y be preferred in the treatment of itching diseases.