Sunscreens: the ounce of prevention.

Sun exposure is linked to visible signs of skin aging, skin cancer, photodermatoses, exacerbation of systemic disease and photoallergic, as well as phototoxic, drug eruptions. Sunscreens vary considerably in their ability to protect patients from exposure to ultraviolet light and its effects. Inappropriate choice and use of sunscreen products can lead to worse problems than using no sunscreen at all. Controversies about sunscreen include adequate level of sun protection factor, appropriate age of users, and whether use of sunscreen products can prevent skin cancer. Instructing patients in how to select and use sunscreen can help prevent or mitigate a variety of cutaneous and systemic diseases.