RESUMO
BACKGROUND: Ultraviolet B (UVB) radiation may cause an immediate inflammatory response followed by a delayed increase in skin pigmentation. The early time course of erythema and pigmentation has so far not been monitored simultaneously by photometric measurements. METHODS: Test areas on the volar forearms of 15 volunteers were irradiated with 210 mJ/cm(2) UVB. Skin erythema and pigmentation were determined photometrically at time 0, after 6 h, and after 1, 2, 3 and 7 days. Punch biopsies were taken before irradiation, after 6 h and after 7 days. Melanocytes were stained using the DOPA method. RESULTS: UVB irradiation caused an increase in skin erythema at all time points, peaking at 24 h and slowly decreasing until day 7. Surprisingly, this was associated with a pronounced decrease in skin pigmentation at early readings. DOPA staining of melanocytes confirmed this observation. Only after 7 days was there an increase in skin pigmentation over the initial levels. CONCLUSIONS: Acute UVB-induced skin erythema seems to be associated with increased susceptibility to the deleterious effects of solar radiation due to a concomitant decrease in skin pigmentation. These findings underline the importance of avoiding even moderate sunburns and of slowly adapting the skin to solar radiation.