Top 6 Sunscreen Mistakes

— -- intro: By now, you probably know that you should use sunscreen every day both to help reduce your risk of skin cancer and to prevent pesky wrinkles, dark spots, and other signs of premature aging. Yet even people who do slather it on religiously make potentially dangerous mistakes.

Here are the most common ways you're messing up with sunscreen, and how to truly protect yourself from UV rays.

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quicklist: 1category: Sunscreen Mistakes to Avoidtitle: You wait until you're outside to apply sunscreenurl:text: How many people have you seen get to the beach, spread out their blankets, strip down to their swimsuits, and then start slathering away?

"You actually want to apply your sunscreen 30 minutes prior to exposure," says Jeannette Graf, MD, assistant clinical professor of dermatology at Mount Sinai Medical Center in New York. That way, it has time to get absorbed and start working—and so you don't get UV exposure for those first few minutes when your skin is vulnerable.

quicklist: 2category: Sunscreen Mistakes to Avoidtitle: You apply sunscreen around your clothesurl:text: Skin cancer can strike anywhere, so it's best to apply sunscreen when you're buck naked. Otherwise, "if you already have a swimsuit or clothing on, you're likely to apply it gingerly so you don't get it on your clothes, which makes you likely to miss a spot or not apply liberally enough," says Noelle Sherber, MD, a consulting dermatologist for the Johns Hopkins Scleroderma Center.

Strip down in front of a full-length mirror, she says, which "helps ensure you entirely cover tricky spots like the mid-back and backs of the legs." (And you should apply before going outside anyway, right?)

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quicklist: 3category: Sunscreen Mistakes to Avoidtitle: You don't protect your lipsurl:text: Just like the rest of your skin, lips are vulnerable to UV rays, so it's extremely important to use sunscreen on your mouth, Dr. Graf says. But don't use the same stuff you use on the rest of your body—it tastes weird and won't last that long on your lips anyway.

Try a lip balm with SPF, which is thicker so it stays on longer. "Then reapply even more frequently than you do body sunscreen, since talking, eating, and drinking removes the sunscreen on your lips faster," she says.

quicklist: 4category: Sunscreen Mistakes to Avoidtitle: You miss other key spotsurl:text: Think you can smear sunscreen on your nose like a 1950s lifeguard and be covered? Unfortunately, there are lot of less-obvious areas people tend to forget—and they're just as important to protect, Dr. Graf says.

"The most commonly missed areas are toes and feet, including the bottoms of your feet; underarms; back of the neck under the hairline; ears, especially the tops and back of your ears; eyelids; and inner upper arms." Put that stuff everywhere.

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quicklist: 5category: Sunscreen Mistakes to Avoidtitle: You sweat (or rinse) it all offurl:text: The small print on your sunscreen label matters, so make sure you're choosing the right sunscreen for your activity, especially if that activity involves sweat, a pool, or the ocean.

"Make sure you get a water-resistant formulation for swimming or activities where you'll perspire, because non-water-resistant formulas can slide right off," says Dr. Sherber. "Plus, they tend to mention migrate into eyes and sting, whereas water-resistant ones won't."

quicklist: 6category: Sunscreen Mistakes to Avoidtitle: You use a body formula on your faceurl:text: It's not just a marketing gimmick: There is a difference between face- and body-specific sunscreens.

"Facial skin is generally more sensitive to irritation than body skin, so face formulations have been tested to cause less irritation and not trigger acne," says Dr. Sherber. "If you're acne-prone or sensitive, avoid the body versions for your face, especially the dry-touch sprays—they're absolutely full of alcohol, which is very drying and irritating for facial skin."

15 Biggest Sunscreen Mistakes originally appeared on Health.com.