Sun exposure, sunscreens, and skin cancer prevention: a year-round concern

OBJECTIVE: To review the role of sunlight in skin aging and skin cancer formation, and to provide guidelines on the use of sunscreens to minimize the adverse effects of sun damage. DATA SOURCES: A MEDLINE search of applicable articles on ultraviolet (UV) radiation, melanoma, sunscreens, and skin cancer, evaluating both human and animal studies. Published and unpublished original research as well as clinical experience were also used. DATA SYNTHESIS: The interaction of UV radiation and skin type plays a central role in melanoma formation. Mortality from melanoma is highest in geographic locations near the equator, where UV intensity is greatest. The incidence of melanomas in light-complected individuals (skin types I-III) is several times higher than those with darker skin types (types IV-VI), even in similar geographic regions. The UVB portion of the spectrum appears to be primarily responsible for skin cancer formation and photoaging, while short wave UVA rays play a significant contributing role. Regular sunscreen use has been shown to reduce the formation of precancerous actinic keratoses (AK) lesions by 36%. A dose-response relationship has also been found between the amount of sunscreen used and AK formation. CONCLUSIONS: Sunscreens have now been shown to reduce the carcinogenic effects of sunlight in humans. Patients should be advised of the long-term consequences of sun exposure and the benefits of regular sunscreen use.