While mascara is a “can’t live without” product in every makeup routine, it’s important to note it actually has one of the shortest shelf lives of any cosmetic. A tube of mascara is at its prime for only about three-to-six months from when you first opened it—and no, you should not keep using it past that, even if there’s still product left over. Applying expired mascara can do far worse damage than leaving you with clumpy-looking lashes—it can also put you at risk for getting an eye infection.