The effect of UV-A and UV-B irradiation on the skin barrier. Skin physiologic, electron microscopy and lipid biochemistry studies]

In order to gain insight into the effects of UV-irradiation on the skin barrier, functional (skin reactivity), electron microscopic and lipid-biochemical studies were performed. In three different irritation models, both UV-A-irradiated and UV-B-irradiated areas proved to be more resistant to damage than normal skin, providing evidence for improvement of barrier function after UV irradiation. Electron microscopic evaluation showed that UV-B induced a significant increase in horny cell layers, whereas after UV-A no change was detected. However, both UV-B and UV-A exposure resulted in an increase in the amount of all stratum corneum lipids. This was also observed in all major ceramide subfractions, which are believed to be the essential lipid constituents for the epidermal barrier function. These findings may explain the known beneficial effects of phototherapy in dermatoses with impaired barrier function, i.e., atopic dermatitis.