We've all been guilty of keeping makeup longer than we should. (Eyeliner from five years ago, anyone?) But different products have shorter or longer shelf lives, depending on their formulation, packaging, and where they're applied.

Here's a handy list of what expires when, from those with the shortest shelf life (mascara) to those with the longest (powders and lip products):

Makeup
-Mascara (regular or waterproof), liquid, pencil or gel eyeliners: 4 to 6 months (a good reason not to buy expensive mascara - you have to throw it out 2-3 times a year!)
-Creamy or liquid foundations and concealers: 6 months to 1 year (Unfortunately, this means you may throw out half-used concealers, depending on how much you use.)
-Powder-based products (including mineral makeup): 2-3 years
-Lipsticks, lip gloss and lip liners: 2-3 years (Don't be afraid to splurge on designer lip color, since it lasts quite a long time!)

Skincare
-Cleansers: 1 year
-Toners: 6 months to 1 year
-Exfoliating products: 1 year
-Facial or body moisturizers and serums: 6 months to 1 year
-Lip balms: 1 year

If anything smells bad before it's time to toss it, throw it out anyway, or go back to the store to return it. There may be something wrong with that particular batch of product. Remember to store any makeup or skincare in a cool, dry place away from the sun. And always wash your hands before and after applying skincare products and makeup.