(RealSimple.com) -- Myth 1: Crossing your legs will give you varicose veins.
Sitting down and crossing your legs won't cause varicose or spider veins, but standing may. Pronounced veins often crop up on people who either have a genetic predisposition to them or have jobs that require them to stand a lot, says Kevin Pinski, a dermatologist in Chicago. Standing makes the vascular network work extra hard to pump blood from the legs up to the heart. If the valves, which keep blood flowing in one direction within your vessels, aren't functioning properly, a pooling of blood can occur and result in unsightly veins. Pregnancy, which puts added pressure on the circulatory system, or a trauma -- getting hit by a softball or a car door, for example -- can also lead to varicose or spider veins.
Myth 2: You can get rid of cellulite.
Ah, if only. "This remains one of the holy grails of cosmetic dermatology," says Timothy Flynn, a clinical professor of dermatology at the University of North Carolina at Chapel Hill School of Medicine. Nothing can be done to permanently eliminate it -- not even liposuction. Cellulite consists of fat deposits that get trapped between the fibrous bands that connect the skin's tissues. The bands squeeze the fat under the skin, resulting in a lumpy texture. Luck of the gene pool mostly determines who will and won't get cellulite. It doesn't matter whether you're fat or thin. You can, however, temporarily reduce its orange peel-like appearance. Firming creams often contain caffeine to tighten and smooth the skin. But a basic moisturizer will also work to hydrate and swell the skin, making cellulite a little less obvious. Or try using a self-tanner. "A fake tan will help camouflage it," says Elizabeth Tanzi, a dermatologist and a codirector of laser surgery at the Washington Institute of Dermatologic Laser Surgery, in Washington, D.C.
Myth 3: Shaving will make your hair grow back darker and thicker.
"Hair that hasn't been cut grows to a point," says Heather Woolery-Lloyd, a dermatologist in Miami. "It's widest at the base and narrowest at the tip." When you shave a hair, you cut it at the base. The widest part then grows out, and the hair appears thicker. But shaving doesn't change the width, density, or color of hair.
Myth 4: Putting Vaseline on your face nightly will prevent wrinkles.
Marilyn Monroe allegedly slathered the thick salve on religiously to stay youthful-looking, but that doesn't mean you should. "Petroleum jelly is the strongest moisturizer there is because it forces oils into the skin and prevents them from evaporating," says Paul Jarrod Frank, a dermatologist in New York City. As the skin ages, it loses its ability to retain moisture, and skin that's dry looks older. "Petroleum jelly can make wrinkles less apparent because it's adding moisture to the skin, which softens lines, but it can't actually prevent aging," Pinski says. Only a cream with a proven active ingredient, such as retinol, can stave off wrinkles. Plus, petroleum jelly is so greasy that it can create other problems, including breakouts.
Myth 5: Wearing nail polish all the time will make your nails turn yellow.
This is true, but you can wear enamel all you like and still avoid discoloration. Nails are porous, and they absorb the pigment in polishes. "Darker colors, especially reds, have more pigment, so they often stain your nails," says Maria Salandra, the owner of Finger Fitness, in Cliffside Park, New Jersey. The solution: Before applying polish, paint on a clear base coat, such as Essie All in One Base Coat ($9.50, essie.com), to prevent nails from absorbing pigment.
Myth 6: You can shrink your pores.
It's actually impossible to change the size of pores, but you can make them look smaller -- and using egg whites, a beauty trick Grandma may have tried, does work. "Egg whites tighten the skin, giving the illusion of smaller pores, but it's a temporary effect," says Elizabeth McBurney, a clinical professor of dermatology at Tulane University School of Medicine, in New Orleans.
Myth 7: If you use wax to remove hair, fewer hairs will grow back.
"Wax rips the hair out at the follicles," explains Woolery-Lloyd. "And any repeated injury to the follicles over time -- we're talking 20 years -- could damage some follicles to the point that they don't grow back." So employ waxing for its ability to keep your legs smoother longer than shaving can, not for diminishing hair growth.
Myth 8: Preparation H deflates puffiness.
This is a secret of makeup artists everywhere, and there's a lot of anecdotal evidence to suggest that this hemorrhoid cream can reduce undereye baggage, but no clinical studies have been done. One of the product's ingredients, a yeast derivative that is said to reduce puffiness, is no longer found in the version that's available in the States. (The cream was reformulated in 1994.) The other ingredient that is credited with reducing inflammation is phenylephrine, which temporarily constricts blood vessels. Nevertheless, using Preparation H around the eyes can cause dry and inflamed skin, says McBurney, so use this only where it's meant to be used, south of the belt line.
Myth 9: Rubbing your eyes creates wrinkles.
You won't get crow's-feet just from kneading your eyes when you're tired, says Frank. But the tug of gravity and the repetitive movement of facial muscles, as in smiling or frowning, can break down the collagen in your skin and create wrinkles over time. So that silly taunt you heard as a child -- "If you keep making that face, it will freeze that way" -- has merit.
Myth 10: Applying cocoa butter or olive oil will stop stretch marks.
Sadly, this isn't true. Stretch marks occur when skin expands quickly (as in pregnancy), breaking the collagen and elastin fibers that normally support it. Or they're simply luck of the genetic draw. "Stretch marks are formed below the top layer of skin, where the cocoa butter and olive oil can't reach," says McBurney. The most either can do is quell the itching that occurs when skin expands.
Myth 11: Brushing your hair 100 strokes a day will make it shine.
Marcia Brady, it turns out, was overzealous in her beauty routine. "One hundred strokes is too much," says Christopher Mackin, a trichologist (someone who studies hair) at the Gil Ferrer Salon, in New York City. "You'll do more damage than good." Hair will break if you tug on it too much. However, gentle brushing -- a few strokes here and there -- will make hair shine by distributing the natural oils from the scalp down the hair shafts and flattening the cuticles to make them reflect more light. More significant, light brushing removes impurities and stimulates blood flow to the scalp, which nourishes hair follicles and keeps them healthy.
Myth 12: Tanning or dotting on toothpaste can help get rid of pimples.
True to both, but don't run for the tanning booth or apply a Colgate face mask. "A particular wavelength of light has been shown to stimulate porphyrin, a chemical that eradicates the bacteria that cause acne," says Pinski. But while some sun exposure may help pimples get better temporarily, you can experience a rebound effect. "If the skin gets dry and damaged from the sun, your body's response is to produce oil," says Frank. Plus, sun exposure can lead to bigger problems, such as premature aging and skin cancer. As for toothpaste, it often contains menthol, which can help dry out a pimple. But other common toothpaste ingredients can irritate the skin. And there are much better over-the-counter options than toothpaste, such as Clinique Acne Solutions Emergency Gel Lotion ($14.50, clinique.com). If, however, you're on a reality-TV survival show and all you have is a tube of the white stuff, a couple of million viewers, and a blemish, a dab on your dot will work.
Myth 13: Sleeping on your back or with a satin pillow will help your face stay wrinkle-free.
That's a big exaggeration with a little truth behind it. As you age, the collagen and elastin fibers in your skin break down, so when you burrow your face into a pillow, putting pressure on these fibers for several hours at a time, the skin is increasingly less likely to snap back. "If you have a pattern of sleeping on one side, that side of your face will typically show more wrinkling than the other," says Tanzi, who adds that the difference is very subtle. Learning to sleep on your back can help your skin a bit, but you'd fare much better wearing a good sunscreen every day than sleeping on a satin pillow, says Woolery-Lloyd.
Myth 14: Rinsing your hair with beer will make it thicker.
A final rinse of beer at the end of your shower will leave you with more voluminous strands. "The beer builds up the circumference of the shafts," says Philip Berkovitz, founder of Philip B. hair products. One caveat: You may smell like a frat house until the scent dissipates. Instead, try a thickening shampoo with hops, such as Aussie Aussome Volume 2 in 1 Shampoo ($4.50, drugstore.com).
Myth 15: Applying mayonnaise to your hair will make it glossier.
Mayo is made with an oil base, and it makes hair shine. But to avoid a mess, try this method: Apply a cup of mayonnaise mixed with a teaspoon of vanilla extract (to cut the mayonnaise scent) to dry, unwashed hair. Cover your head with a warm towel to help the mayonnaise penetrate, and leave it on for 20 minutes. Before you step into the shower, apply a heaping handful of shampoo to your hair. Don't add any water yet; just massage it in thoroughly for several minutes. That will help break down the excess oil, says Berkovitz. Rinse with cool water in the shower and your hair will come out shiny and silky. If the idea of putting a condiment in your hair makes you queasy, try a rich glossing treatment, such as Phytonectar Ultra-Nourishing Oil Treatment ($30, drugstore.com), which contains egg and rich oils, the basic ingredients in mayonnaise.
Myth 16: Never pluck a gray hair, because 10 more will grow in its place.
This is false. "How can you get 10 new hair follicles from plucking one?" asks Berkovitz. If anything, ripping a hair out by its root leads to regrowth that refuses to lie flat. Your best bet for conquering gray? See a colorist.
Myth 17: Hair grows faster in summer than in winter.
Although studies have shown that men's beards grow faster in summer, there is no evidence to suggest that the hair on your head does. Many women say they can tell it grows faster then, but if so, the difference is slight and barely detectable, according to McBurney. The only time women's hair has been proven to grow faster is during pregnancy, thanks to increased hormones.
Myth 18: Drinking water keeps your skin from drying out.
"This is one of the biggest myths out there," says Frank. What keeps skin moist is oil, not water. Certainly, drinking water helps vital organs operate properly, and too little water in your body can give you a wan appearance. But your skin can still look dry even if you drink eight glasses a day.
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