Ew! Your old makeup could be rife with bacteria.

Most women never think about expiration dates for their moisturizer, mascara or lip gloss, but such diligence could prevent skin infections, eye infections and conjunctivitis. Makeup, like food, should be promptly used or thrown away.

This covers everything that touches your face--sunscreen, bronzer, moisturizer, blush and mascara to name a few. This may come as news to most women, who tend to keep makeup until it's gone. Not a good idea, says Betsy Stephens of "All You Magazine." For example, she told CBS News that mascara should be tossed in the trash after three months. "When you are using mascara, the recommendation is to not pump the mascara," she explained to CBS News. "If you need to, you can swirl the brush around."

Even more susceptible to airborne bacteria is makeup made from natural products. Typically they don't last longer than six months. "Just like milk, if milk starts smelling bad and looking lumpy you are not going to want to drink it. The same thing applies to makeup," Stephens told CBS.

• Mascara

• Facial moisturizer
• Foundation
• Concealer
• Eye Shadow
• Lipstick
• Lip gloss
• Facial powder
• Facial blush

• Bronzer

• Sunscreen (but remember it can lose its effectiveness over time)

The countdown to the expiration date begins when you break the seal and airborne bacteria can enter the makeup product. It may be hard to throw it away, but the consequence could be much more difficult and costly.