Woman in grass with sunhat on

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Lie: Eighty percent of your lifetime sun damage occurs before age 18

"This statistic had become almost a mantra among dermatologists," says Katie Rodan, MD, adjunct assistant professor of dermatology at Stanford University School of Medicine. "But now we're very happy to be proved wrong." A recent study revealed that we actually get only 23 percent of our total UV exposure by age 18. At 40 it reaches about 46 percent; by 59, 74 percent. "No one can say anymore, 'I've already blown it,'" says Rodan. "You can still prevent sun-induced aging by getting serious about sunscreen."
Woman with concealer on

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Lie: Sleep deprivation causes dark undereye circles

Sleep deprivation can lead to many things—memory lapses and weight gain among them. But you can thank your folks for the shadows under your eyes. "Dark undereye circles are the result of a concentration of veins beneath the very thin skin in that area," says David J. Leffell, MD, professor of dermatology at Yale School of Medicine. "They're determined by genetics and won't change with more or less sleep." Frequent late nights may cause fluid retention under your eyes, however, and that puffiness can draw attention to existing darkness there.
Woman eating chocolate

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Lie: Greasy food and chocolate cause breakouts

Have you ever heard this one debunked before? Then why do you still believe it? The truth is that sushi and shellfish are the only foods that may exacerbate acne, because of their high iodine content, says Diane Berson, MD, assistant professor of dermatology at Weil Medical College of Cornell University.
Woman drinking water

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Lie: Drinking lots of water hydrates the skin

The moisture level in your skin is affected by environment (low humidity or harsh winds) and age (oil production slows over time), but not by how many trips you make to the watercooler. "You can hydrate the skin only from the outside, with moisturizer," says Rodan. "Skin isn't like a plant that wilts and then perks up with a drink of water." If you became extremely dehydrated (usually as a result of illness), your skin could begin to look sallow. (You'd also probably start to feel weak and dizzy.) "But as long as you respond to your thirst, your body will be maximally hydrated," says Dennis Gross, MD, associate clinical professor of dermatology at New York University Medical Center.
Woman crossing legs

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Lie: Crossing your legs causes varicose veins

Genetics, pregnancy, and spending long periods of time on your feet cause varicose veins. "Crossing your legs does put some pressure on your veins, but you would have to keep them crossed 12 hours a day for months at a time to see an effect on the formation of varicose veins," says Berson.

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