Ultraviolet: Long‐Term Risks and Benefits

The immediate hazards from ultraviolet (UV) exposure of the skin are erythema and sunburn; and to the eyes, photokeratosis, such as snow blindness. UV also causes skin aging or "photoaging", a loss of elasticity due to loss of interstitial collagens, showing as sagging cheeks, deeper facial wrinkles, and skin discoloration. Tanning is a protective response; immediate tanning results from oxidation of existing melanin, while tanning over a few days is due to the formation of new melanin, providing some protection against further UV damage. In recent years, the potential benefits of vitamin D have received much attention, going well beyond the bone and joint effects. Increasing vitamin D by increasing sun exposure has to be weighed against the dangers of increasing skin cancers. The evaluation of the effectiveness of sun exposure modification programmes is complex, and methods range from formal randomized trials of programmes for schools or work places, to community surveys.