Effects of single doses of UVA, UVB, and UVC on skin blood flow, water content, and barrier function measured by laser-Doppler flowmetry, optothermal infrared spectrometry, and evaporimetry.

The effect of single doses of ultraviolet (UV) radiation was studied in 6 healthy men of skin Type III. Test areas on the forearm were irradiated with 150 J/cm2 UVA, 0.5 MED, 1 MED, and 3 MED UVB, and 1 MED UVC. Test areas and control areas were followed up for 1 month by clinical assessment, laser-Doppler flowmetry, evaporimetry, and optothermal infrared spectrometry (OTIS). UVA produced immediate erythema; the reaction appeared later with the other wavelength regions. All responses peaked after 12-24 h. The degree of erythema of UV-induced inflammation assessed visually correlated closely with the increase in skin blood flow registered with the laser-Doppler flowmeter. No increase in transepidermal water loss, indicating damage to the epidermal barrier, could be recorded by evaporimetry except on the area irradiated with 3 MED of UVB, where 4 subjects showed a moderate increase after 2 weeks. Changes in water content in the uppermost part of the epidermis, mainly in the stratum corneum, were detected by OTIS. A decrease took place that was most pronounced in the area irradiated with 3 MED UVB. This decrease in the OTIS signal is probably due to a combination of increased thickness and decreased water content of stratum corneum. We believe that these 3 noninvasive methods, especially in combination, are useful in the evaluation of different aspects of UV reactions.