Exposure of skin to sunlight is beneficial in moderation since ultraviolet radiation is vital to the synthesis of vitamin D and hence to satisfactory skeletal development. Excessive exposure, however, is hazardous, particularly in light-skinned persons who tan poorly, and in patients who are photosensitive. There is also evidence that ultraviolet light decreases the immunological responses of the skin.

Photodamage is first evident as acute sunburn and, in the longer term, as premature ageing of the skin. Excessive exposure to sunlight also predisposes to the development of malignant and premalignant skin lesions, including actinic keratosis, squamous cell and basal cell carcinoma, and malignant melanoma.

The incidence of malignant and premalignant conditions is particularly high among light-skinned persons living in hot sunny climates and in dark-skinned persons with vitiligo or albinism. Many cases could be prevented by persuading parents and individuals directly at risk of the importance of avoiding sunburn and reducing exposure to solar radiation. Photoprotection in children is a priority all over the world, and every effort should be made to institute educational programmes on protection against the sun at a very early age. The use of protective clothing (e.g. tightly woven fabrics, wide-brimmed hats, long sleeves and long trousers) is highly effective. When this is not practicable or acceptable, it is important to encourage regular use of sunscreen products with a SPF rating of at least 15. People should understand that the atmosphere has a filtering effect on ultraviolet light and, therefore, they should avoid exposure at midday when the sun is most vertical and the light passes through less of the atmosphere.