With sunscreen, the number matters. “An SPF less than 30 doesn’t afford you the level of sun protection that you need,” says Deanne Mraz Robinson, MD, FAAD, a dermatologist at Connecticut Dermatology Group. Higher is also important because you’re unlikely to apply the sunscreen well enough to reach full protection. “The average person applies 25 to 50 percent of the recommended amount of sunscreen,” says Adrienne Haughton, MD, director of clinical and cosmetic dermatologist at Stony Brook Medicine at Commack in New York. “In one study, patients applying what they perceived as an adequate amount of sunscreen labeled SPF of 70 and 100 provided an actual SPF of 19 and 27 percent respectively.”

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