Heard these skin care myths before? Stress causes wrinkles. Toothpaste gets rid of pimples. Shaving facial hair makes it grow back thicker.

Chances are you're familiar with such beauty claims. But are they fact or fiction? To help dispel some of the most common -- and strangest -- skin care myths, our expert weighed in on which ones we should listen to and which ones are just pore-clogging myths.

Woman sunbathing skin care myth

Laying out in the sun without UV protection has its skin care consequences. Photo: Alamy

Myth: Stress causes wrinkles.
True. According to Manhattan-based dermatologist Amy Wechsler, cortisol (the hormone caused by stress) degrades collagen. A wrinkle is a weakening and lessening of collagen and elastin fibers in the skin's dermis. When you live in a chronic state of stress, routinely bathing your body in cortisol, it becomes harder and harder for the skin to repair itself naturally.

Myth: A day at the beach or a visit to the tanning parlor will get rid of my pimples.
False. The sun is deceptive. "An hour on the beach may dry up your acne a bit so it looks better tomorrow," said Wechsler, "but a few days later, more bumps, inflammation and redness can occur." Your skin reacts to the UV radiation by becoming inflamed. It reacts to the stress of those damaging rays with its own stress-response system, which can trigger acne and other troubling skin conditions. So cover up!

Myth: Toothpaste will dry out pimples.
False. It will just irritate the skin. "For some reason, people think using toothpaste will dry out pimples, but it won't," said Wechsler.

Myth: Picking at a pimple will cause a scar.
False. You would have to pick really deep to make a scar. But, what can happen when you pick at a pimple is discoloration of the skin. This can be even harder to treat than the actual pimple itself.

Myth: Moisturizer will make breakouts worse.
False. Your skin still needs moisture. Even oily skin needs moisture. Acne meds are often very drying, so you may need more moisturizer, not less, when fighting breakouts. "Otherwise, the overdryness may trigger inflammation, then you're back where you started: dealing with more acne," said Wechsler. Just be sure to buy a formula that's non-acnegenic (look for the term "noncomedogenic"). For practical purposes, if it's labeled "oil-free," you're OK.

Myth: Tanning beds are safe for your skin.
False. Tanning beds are not safe because the UV rays are more highly concentrated, and you are exposed to a lot of UVA rays. The only way to get a perfect tan with no strap marks or red zones -- just an even glowing gold -- is with a sunless tanner. Whether professionally sprayed on or DIYed at home, they can work amazingly well.

Myth: You don't need SPF on a cloudy day or in the winter.
False. Even when it's overcast, 80 percent of UV light seeps through the clouds. Before heading outdoors, use 1 teaspoon's worth of broad-spectrum sunscreen with an SPF of 30 or higher on your face and apply at least 3 ounces -- two shot glasses -- of sunscreen to the body.

Woman cold rinse face skin care myth

You might want to think twice before your next cold rinse. Photo: Alamy

Myth: Cold rinses are good for your skin.
They don't do anything other than make you cold, according to Wechsler.

Myth: Junk food causes acne.
False. Foods like chocolate, soda, pizza, potato chips, French fries and anything else that seems bad or forbidden usually gets blamed for breakouts. "But there's barely a lick of evidence showing any of them (or any food) produces pimples," said Wechsler. "I'm not convinced that all bad foods lead to pimples."

Myth: Shaving facial hair makes it grow back thicker.
False. Shaving simply puts all of the hairs in the same phase of the growth cycle so they appear as if the hair grows back thicker.

Myth: Switching facial soaps occasionally is good.
False. It doesn't make a difference. Your skin is not likely to get used to a product's ingredients in a way that decreases its effectiveness. "Many women feel that if they are not using the latest products, they are somehow missing out," said Wechsler. "The only products that may become less effective over time are over-the-counter acne treatments if your acne progresses and you're using a formula that is too mild."

Myth: Peels are good for your skin.
True. Once or twice a month, chemical peels are good for your skin to remove dead skin cells and stimulate new cell growth. This can reveal a healthy, fresh glow.

Myth: Antiaging creams can erase wrinkles
False. The only proven wrinkle reducers and age fighters are retinoids. Two are prescription-only derivatives of Vitamin A: tretinoin (brand names: Retin-A, Avita, Renova) and tazarotene (Tazorac, Avage). They are FDA-approved, rub-on treatments that rank high on Wechsler's list of skin-renewing candidates.

Myth: The more expensive the product, the better
False. Many drugstore brands are excellent, and the larger companies spend a lot of money on research and development of their products. Expensive products sometimes look better because those companies spend more money on packaging.

Know what else is fact and fiction? Check out the top hair care myths!