3. Shaving will make your hair grow back darker and thicker.

False. "Hair that hasn't been cut grows to a point," says Woolery-Lloyd. "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.

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. "Petrolatum 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, petrolatum is so greasy that it can create other problems, including breakouts.