When's the last time you gave your makeup bag a thorough clean out? If it's been few months, or -- gulp -- years, there's a good chance more than a few of your products have expired.

To make sure the cosmetics you apply are safe and effective, celebrity makeup artist Jamie Greenberg says to use your senses. "You need to smell your makeup," Greenberg says. If something's off, your nose knows -- and that means it's time to toss.

In the above #OWNSHOW video, Greenberg goes six makeup expiration dates you need to know and gives helpful tips for making your products last.

Eyeliner: 6 months to 1 year
Gel eyeliner only lasts six to eight months because you're constantly double-dipping a brush into a pot, says Greenberg. A pencil, on the other hand, has a shelf life of one year. "If you're using a pencil, you can sharpen it and it's not going to be a breeding ground [for bacteria] as much," she says.

Mascara: 3-6 months
To get the full six months out of your mascara, don't make this common mistake. "A lot of us pump our mascara to get more on there," Greenberg says. "That actually lets air in there, it dries out the formula and you're also letting in bacteria."

Blush, eye shadow, and other powder cosmetics: 1-2 years
Powder lasts longer than wet formulas, but Greenberg warns to check them periodically. "If the formula changes at all, toss it. If it smells, toss it. And if the color goes out of style, toss it!"

Foundation: 6 months to 2 years
Foundation packaged in a pot expires in about 6 months, whereas a pump formula can last one to two years. When your foundation expires, look at it as an opportunity to try something new. "I think your skin gets used to having that formula on it," she says. "Try a new foundation after the pump is over."

Lipstick: 2 years
Change in color, texture or smell are all big warning signs that your lipstick has expired. If your lipsticks pass the test, Greenberg says to just things clean. "Clean them off, wipe them off, spray them with a little bit of alcohol just to keep them sanitized."

Natural products: 3-6 months
Think of your natural, preservative-free cosmetics as food, Greenberg says. "If you keep them in your refrigerator they'll last a little longer, but the natural stuff is going to go way quicker," she warns.

More from #OWNSHOW: Greenberg walks through the steps to create the perfect cat eye.

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