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Dermatologists tell us we need to use about half a teaspoon of sunscreen on our face in order to get the SPF protection listed on the tube. That seemed like a lot, so one recent morning, I squeezed my daily sunscreen into a half-teaspoon measure and tried to rub it in. After a few minutes, my face had taken on a glossy sheen, except for a few patches where my skin had apparently reached its saturation point and the white cream sat on it like custard. I never wear that much sunscreen, and you probably don't, either. That means it's highly unlikely we're getting the SPF protection we think we are. Studies have shown that we actually apply only 20 to 50 percent of the amount of sunscreen used to test SPF, says Darrell Rigel, MD, clinical professor of dermatology at New York University Medical Center. If you use 50 percent of the necessary amount of an SPF 30, your protection is about an SPF 8; if you use 25 percent, it's less than an SPF 5. Uh-oh.
The bottom line: To get the most protection, apply as much sunscreen as you can comfortably rub in (before a day at the beach, at least two tablespoons head to toe), reapply every two hours, and use a higher SPF to compensate for inevitable underapplication, says Rigel. And make sunscreen part of a strategy that also includes a wide-brimmed hat (at least two and a quarter inches all the way around), sunglasses, and protective clothing.