Sunscreen

Ever seen a dermatologist trying to get a suntan? We didn’t think so.

Dermatologists know all too well the effect of sun on skin and, as a result, the importance wearing sunscreen. Also called sunblock, sunscreens work by blocking or absorbing ultraviolet (UV) radiation in sunlight—a known risk factor for skin cancer (including melanoma, its deadliest form). Short-wave UVB rays, which cause sunburn, injure the top layers of the epidermis (the skin’s outer layer). That not only increases your risk of skin cancer, it creates wrinkles as well. UVA, or long-wave, rays are also damaging. They don’t cause sunburn, but they reach deep into the skin, harming cell DNA. Protecting yourself from ultraviolet radiation is particularly important these days: The ozone layer in Earth’s atmosphere, which absorbs UV rays, has thinned, making these rays an even greater threat.

Sunscreens contain a mix of active ingredients that fall into two categories: Chemical absorbers (such as aminobenzoic acid, avobenzone, ecamsule, and oxybenzone) work by absorbing radiation; physical blockers (the minerals titanium dioxide and zinc oxide) work by reflecting and scattering rays. Because chemical absorbers penetrate the skin, they’re more commonly linked to skin irritation. Physical blockers aren’t absorbed, so they’re considered the safest choice for kids.

What most distinguishes one sunscreen from another, however, is its “sun protection factor,” or SPF. The number indicates how long the sunscreens protection lasts. So an SPF 15 sunscreen allows you to stay in the sun without burning 15 times longer than you could if your skin was bare. The Skin Cancer Foundation recommends wearing an SPF of at least 15, but there are advantages to going higher. It’s not so much that they block many more rays—SPF 15 products block 93 percent of rays, SPF 50 lotions, 98 percent. But because higher-SPF products have more active ingredients per centimeter than lower-SPF lotions, they tend to keep protection from slipping too low when factors like sweat, water, and towel-drying bring it down.

SPF isn’t everything, though. Unfortunately, the SPF number applies only to UVB rays. And the U.S. Food and Drug Administration (FDA) has yet to devise a system for measuring a sunscreen’s UVA-blocking ability. Until it does, the best you can do is look for the words “broad spectrum” on the label. Also, check the ingredients list: avobenzone, ecamsule, and zinc oxide provide the most UVA coverage.

In a 2008 study, the Environmental Working Group cited this lack of UVA protection when they found that only 14 percent of 1,082 sunscreens met their criteria for safety and effectiveness. Of particular concern to the EWG are nanoparticles—tiny versions of titanium dioxide and zinc oxide, made smaller so they’re less visible on the skin. The safety of nanoparticles, and the cost to the environment when they’re released into the waste stream, isn’t known.