SKIN TEMPERATURE AND PHOTOTEST EVALUATION

The degree of erythema following UV irradiation is known to depend upo n skin temperature at the time of UV exposure. We investigated whether changes in skin temperature at the time of erythema assessment influe nced the level of erythema. Twenty-two healthy people (mean age 26 yea rs) were irradiated with solar simulated radiation on previously UV un -exposed buttock skin. The erythematous reactions were evaluated 20-24 h after irradiation by visual scoring and by measurements of skin ref lectance and laser Doppler flowmetry. The readings were done at the ba seline level at 21 degrees C room temperature where skin temperature w as 30.0+/-1.7 degrees C and subsequently after skin warming to 37.2+/- 2.5 degrees C and after cooling to 22.8+/-2.6 degrees C. After skin wa rming, a clinically evaluated erythema grade [0, (+), +, ++, +++] was scored higher for at least one reaction in 10 of 22 individuals (45%). In the same proportion of subjects, changes to lower erythema grades were detected upon cooling. Skin warming caused an increase in laser D oppler blood flux, but skin cooling did not have a significant effect on cutaneous perfusion. Skin redness measured by skin reflectance was relatively stable during the cooling phase, but a significant increase in skin redness was noted for O reaction upon skin warming. For ++ an d +++ reactions a small but significant decrease in reflectance was no ted. Our results indicate that alterations in skin temperature, especi ally a temperature increase, modulates the degree of UV-induced erythe ma moderately. The temperature-dependent changes as an assessment of t he (+) reaction are of practical significance, since this reaction is used for the assessment of cutaneous photosensitivity.