 Using old makeup could be destroying your skin. When makeup expires, you run the risk of getting infections like pink eye, painful breakouts, and even allergic reactions. Something like mascara can get contaminated and should be thrown away about three months after it's opened. Eyeliner should be thrown out after a year and foundation should be used within six months. To avoid damaging your glow, you can check that little open bottle icon on the product, which tells you how many months or years the product will stay fresh once it's opened.