A: We go to so much trouble to keep our skin clean and healthy, the last thing you want is to contaminate it with old, possible unsafe cosmetics. Here's a handy guide to the shelf life of already opened products:

Cleanser: 1 year
Foundation: 1 year (avoid sticking your fingers in the container)
Lipstick: 1 to 2 years
Mascara: 3 to 4 months, especially if you wear contact lenses or have sensitive eyes
Face Powder: 6 months
Eye Shadow: 2 years
Blush: 2 years
Lip Liner: 3 years or longer
Eye Liner: 6 months (since it's applied so close to the eye)
Moisturizer: 1 year (try keeping it in the fridge for longer life)
Eye Cream: 3 to 6 months (again, refrigerating helps)

When in doubt, check the odor, color and consistency of a product you think might be too old to use. It is looks, smells, or feels bad or "off", throw it out!

Knowing how long your products will keep for not only protects your skin, but it's a great way to monitor your buying habits; if you keep buying creams that end up going bad because you don't use them, you'll know to buy only what you will actually use.