Cosmetics Quiz: The Truth About Your Makeup

Mascara can flake into your eyes while you sleep. You might wake up with itchy, bloodshot eyes, scratched corneas, or even an infection. Make sure to remove all makeup before you go to bed.

Sheer, high-gloss lipsticks offer little protection and can attract damaging UV rays to your lips. If you want the wet look, apply an opaque lipstick first, then top with the gloss. Use a lip balm with at least SPF 30.

Nail polish, particularly darker colors, may stain your fingernails or toenails and leave them yellowed and discolored. The stained nails will grow out, but it may take several months.

Just because a product says it's hypoallergenic doesn't mean you won't have a reaction to it. The FDA doesn't have standards for using the term "hypoallergenic," so cosmetic makers don't have to prove their claims. Any product can be labeled "hypoallergenic" no matter what its ingredients, and no cosmetic product can be guaranteed not to cause an allergic reaction.

Because of the risk of eye infections, you may not be able to use eye makeup, including mascara, eyeliner, and eye shadow, as long as you would other products. Liquid or creamy makeup can harbor bacteria more easily, so some experts recommend replacing your mascara every three months. If mascara dries out, don't add water or saliva to moisten it. That can introduce bacteria.

Cosmetic brushes, sponges, and fingertips pick up bacteria and other germs from the skin, so sharing makeup can mean you're also sharing bacteria. (Moistening brushes with saliva makes this worse.) Extended exposure to light or heat can break down the preservatives that fight bacteria, so don't leave your makeup in a hot car. And don't use cosmetics if you have an eye infection like pinkeye. Throw away any makeup you were using when you discovered the infection.

While some lipsticks do contain small amounts of lead, lipstick is intended for external use only, and you probably swallow only very small amounts of it. The FDA has concluded that lead levels in lipsticks aren't a safety concern.

Kohl is a traditional type of eye makeup that can contain significant amounts of lead. It's not permitted for use as an additive in any cosmetic or FDA-regulated product in the U.S., but it has been advertised for mail order online.  Some types of eye makeup may be labeled with the term “kohl” to indicate the shade, but the product doesn’t actually contain kohl.

A cosmetics maker can sell products without FDA approval. The FDA does not review or approve cosmetic products or any cosmetic ingredients, with the exception of color additives, which are required to have safety testing.

The FDA doesn't require cosmetics makers to submit information about any injuries caused by their products and doesn't issue cosmetics recalls, though it can request recalls by the manufacturer. It also monitors ongoing recalls. A product can be taken off the market only if the FDA proves in court that it is dangerous or breaks the law.

Scratching the eye with a mascara wand is the most common cosmetics-related injury. It can lead to an eye infection if the scratches go untreated, and infections can result in ulcers on the cornea, eyelash loss, or even blindness. To avoid this type of injury, don't try to apply mascara while driving or riding in a moving vehicle.

“Cosmeceutical” is a popular term for a product that's meant to beautify but also treats a condition. However, the FDA classifies a product as either a cosmetic or a drug based on its intended use; it doesn’t recognize any category that’s a combination of the two. A company that associates a drug claim with a product the FDA has classified as a cosmetic may be violating federal law.

According to the American Cancer Society, based on available data, "there is little evidence to suggest that using cosmetics, or being exposed to the ingredients in cosmetics during normal use of these products, increases cancer risk." But certain products may have not been thoroughly tested, so more research is needed.