Bath oils and gels: Exposing these products to air and water alters the natural ingredients and makes them less effective. And since these products win the “most likely to get dropped in the bathtub” award, it should be no surprise they have a shorter shelf life.

Sunscreen: Just like perfume, you want to keep your sunscreen in a cool place — not on your towel or in your car. If you do so, the “active ingredients will remain effective for 12 months,” says Jennifer Taylor, creator of sunscreen brand Smart Girls Who Surf. But if your sunscreen does heat up, the active ingredients become less effective against preventing sun damage.

Ways to tell your SPF has expired: It smells “medicine-like,” comes out runny, or has changed colors, from white to yellow, says Taylor.