[Effect of sunlight on the skin--what have we learned?].

Ultraviolet radiation (UVR) exerts a variety of effects on the skin, most of which are inimical. Best known is the effect of UVB radiation which readily burns unprotected skin, but we now know that even UVA radiation may exert penetrating effects on the skin, as well as causing DNA damage and increased risk of cancer. The markedly increased incidence of basal cell and squamous cell carcinoma and malignant melanoma among fair-skinned Caucasians in industrialised countries is attributed to increased exposure to UVR. Sunscreen creams may have exacerbated the situation. Effective phototherapy is a useful product of photomedical research, and it can be further improved. Recently new perspectives were opened up in basic research into UVR, when it was found that repair of DNA lesions via different pathways orchestrates a series of cellular phenomena such as oncogene expression, acid radical defence, immunomodulation, apoptosis and pigmentation induction.