INTENSITY AND AREA INCREASE OF UVB-INDUCED ERYTHEMA - 2 VARIABLES USED FOR STUDIES OF THE INFLUENCE OF TOPICALLY APPLIED DRUGS

The area of UV erythema produced by a small beam head was found to inc rease with increasing doses. The aim was to investigate whether measur ement of the area could be a more useful indicator of UV-induced damag e than classic visual grading. Topical pretreatment with all-trans ret inoic acid (tretinoin) and betamethasone valerate was used to test the applicability of the method in pharmacological studies. We used a rou nd outlet head (5 mm2) connected by optical fibre to a monochromatic i rradiator, and doses ranging from 0.05 to 0.2 Joule of 300 mm UV light were applied to the skin of 6 healthy subjects. Erythemal area was ca lculated by the measurement of two diameters, and intensity was graded visually (0-6 scale). The area of the erythema correlated with the in crease in intensity up to score 6. Area measurement was less subject t o intra-investigators' variability than the intensity score. By multip lying intensity by area, a good indicator of UV-induced reactivity was obtained. Pretreatment with betamethasone valerate decreased the area of erythema, as did tretinoin 12 h after irradiation. Thus, area meas urement of erythema is a useful adjunct to visual grading of UV-induce d skin reactions.