The effect of ultraviolet radiation on the water-reservoir functions of the stratum corneum.

The stratum corneum plays an important role in keeping the skin surface supple and flexible. After exposure to sunlight, the skin may become dry and scaly. In the present study, the water content, hygroscopicity and water-holding capacity of the stratum corneum were examined after ultraviolet B (UVB) exposure to the guinea pig skin. Manually depilated back skin was exposed once to 1, 2 and 3 times the minimal erythema dose of UVB, and a time course study was performed. Our study demonstrated the following: The water content, water-holding capacity and hygroscopicity decreased after UVB irradiation. They decreased roughly dependent on UVB dose. The decreased water content and water-holding capacity were noted on day 1 and persisted until day 10 to 14. In contrast, the decrease in hygroscopicity became apparent 3 days after exposure and returned to the preirradiated state on day 7. The impaired functional parameters were partially prevented by topical application of a sunscreen. These results indicate that a single exposure to UVB can damage the function of the stratum corneum.