You probably wouldn't eat food past its expiration date, so why put expired makeup on your lips and the rest of your face? It may surprise you, but just like food, makeup has expiration dates. The trick is to know how quickly your products expire and to keep track of when you bought them. Sound like a lot of trouble? It's not when you consider the repercussions of using old makeup, which can cause eye infections, acne, cold sores (aka herpes), staph infections and more. Where women tend to keep their makeup - the warm, moist, dark bathroom environment - is a perfect breeding ground for bacteria. What's amazing is that most women will use old makeup, regardless of the risks. According to a UK study, researchers found that 66 percent of women knowingly used expired makeup. Unfortunately in the United States, the FDA doesn't require expiration dates on cosmetics; however, some companies do provide them voluntarily.