Is there a dark side to the sun? The government has placed ultraviolet radiation (UVR) both from the sun and from tanning machines on its list of known human carcinogens. UVR produces DNA damage that may lead to mutations in genes involved in the pathogenesis of skin cancer. Therefore, along with other sun safety strategies, sunscreens that absorb or block UVR serve an important protective function. The US Environmental Protection Agency estimates that the sun causes 90 percent of nonmelanoma skin cancers and 65 percent of melanoma. Each year, there are an estimated million or more new cases. The incidence of invasive melanoma, the most serious form of skin cancer, is estimated to be 59,940 this year, with deaths estimated to be 8,100, according to the American Cancer Society. Photoaging is another long-term result of sun exposure. While not threatening to life, it is threatening to quality of life. Excessive unprotected time in the sun leads to premature wrinkling, sagging, a leathery texture and hyperpigmentation. Fairskinned individuals are at highest risk for skin cancer. They have blond or red hair, blue or hazel eyes, burn easily and tan minimally or not at all. People with many moles or any large, atypical moles are also at higher risk. Finally, not just intermittent intense exposure, but also chronic lifetime exposure adds to skin cancer risk. Although people with dark skin are not as high-risk as those with light skin, they develop skin cancer too and should use sunscreen. Everyone over the age of six months should use sunscreen daily year-round, in any weather. Infants should be kept out of the sun or protected with clothing and an umbrella or strollerhood. Sunscreen should not be neglected on overcast days, as 70-80 percent of the sun’s rays go through clouds and fog. In addition, according to the World Health Organization, UVR levels rise by about 10-21 percent for every 1000 feet of altitude, and reflection from sand, water, snow or concrete and magnifies their effects by up to 80 percent. Sunscreen should be applied one-half hour before going outside. At least one ounce (two tablespoons) is needed to cover the entire body surface. As facial skin is thin and highly exposed, it is particularly important to apply sunscreen there liberally. There is no need to throw away last year’s left-over sunscreens. Shelf life is at least two years. Sun Protection Factor (SPF) is a reliable measurement of protection against UVB. SPF 15 sunscreen might prevent reddening 15 times longer—about five hours. That figure is theoretical, however, and sun damage can occur even without reddening, so dermatologists normally advise reapplying after approximately two hours. Many people mistakenly believe that an SPF 30 rating gives twice as much sun protection as an SPF 15 and an SPF 50 more than three times that much; tests have shown that SPF 15 sunscreens filter out 93% of UVB rays, while SPF 30 protects against 97% and SPF 50 98%. There is no such thing as a healthy tan. Therefore, if people insist on being bronzed, they should be advised to use self-tanners, now offered by many cosmetics companies. For best results, if you are using a moisturizer and a separate sunscreen, the moisturizer should go on first, then sunscreen, then makeup. If you are also using a topical medication, that should be applied before everything else, then the rest of the layering process is repeated. Individuals at risk for vitamin D insufficiency, such as those who are elderly, homebound, or dark-skinned, a balanced diet with adequate intake of food rich in vitamin D (e.g., salmon and fortified milk) is the most appropriate way to maintain a good vitamin D level. If necessary, vitamin D supplements can be added. Because of it’s potentially damaging effects, unprotected sun exposure should not be used as a way to increase vitamin D level. So now that the heat is upon us, don’t forget to protect yourself and your children, use umbrellas and wide brimmed hats, and don’t forget your Sunscreen!! Dr. Liz Smith D.C.