It’s a dilemma many women (and some men) are forced to face: When is it time to let go of your favorite makeup products? And although some of us may be guilty of having a lip gloss at the bottom of our makeup bags that’s older than we’d like to admit, in reality, makeup is not immortal and prone to picking up some nasty germs. Here’s an easy guide to figuring out when it may be time to let go.

According to InStyle, mascara is the makeup product with one of the shortest lifespans, and you really shouldn’t be using it for longer than three months. This is because mascara is a breeding ground for bacteria and the last place we want all this bacteria is near our eyes. On the same page, gel and liquid eyeliners shouldn’t be kept for much longer than six months as well. According to All You, although pencil eyeliners have a bit more leeway because they are constantly filed down, they probably shouldn't be kept for longer than a year.

Makeup products meant for your face can last a little longer but they still can grow bacteria that can present health risks to your skin. For this reason, it's best to replace foundations and concealers after about a year, PopSugar reported. However, like mascaras, lip glosses should be tossed every six months, although lipsticks can last about twice as long as that.

The longest-lasting makeup products are those which are powder based, such as eyeshadows and blushes, and can be kept for up to two years.