Makeup-bag edit: What to keep, toss and why

Nice Package

"If you're sticking your fingers in a jar, bacteria are more likely to grow than if a product is delivered from an airtight pump," says Washington, D.C.–based dermatologist Elizabeth Tanzi. Also, products in opaque containers tend to last longer than those in clear packaging, since UV rays can make ingredients less effective. Mark the purchase date of all products, and toss paraben-free ones after 6 months (parabens are preservatives), and regular ones after two years.

Takeaway tip: Heat and sun degrade formulas, so don't store products on your bathroom windowsill.

Touching Base

Your base is meant to hide flaws, not create them. But if you're noticing sudden breakouts, your foundation may be past its prime. "Separation, texture or color changes are signs that the product is expiring and bacterial overgrowth can lead to breakouts," says Tanzi. Pumps can last 18 months, ditto for powder formulas. But any cream formulas that you dip your fingers into need to go as early as six months after opening.

Takeaway tip: Store in a cool, dry spot and keep bottles tightly closed. Repeated exposure to air will cause thickening.

Undercover Agent

Too-old concealer can clog pores and cause pimples. Powder, stick and pencil formulas are most resistant to bacteria; as long as they don't turn dry and chalky, you can hang onto them for up to a year, according to Dallas-based aesthetician Renée Rouleau. Watch out for liquids and creams, though, which can expire in as quickly as six months. Toss if they start to get tacky—and not in The Real Housewives way.

Takeaway tip: Use a tissue soaked in rubbing alcohol to wipe down sponge-applicators, tube rims, and sticks and sharpen concealer pencils weekly.

Getting Cheeky

"For blush and bronzer, the same general rules apply," says Rouleau. "Are you sticking your fingers in it or not?" Toss pots if you've had them for about six months. Creams and gels in squeeze-out tubes can last a year. Powder, meanwhile, can keep you beautifully blushing till the two-year mark.

Takeaway tip: "Age can lower the pH of a product, making it more acidic and potentially irritating," says Rouleau. So be aware if you're rosacea-prone or have sensitive skin.

Powder Keg

The good news: "Bacteria generally don't survive in a dry environment," says Rouleau. So you may maintain a two-year relationship with your pressed powder. The bad news: After awhile, instead of translucencent shine-busting, the look you get is cakey and masklike. Each time you dust powder on using the in-compact applicator, oils from your face move back to the powder. This can lead to a hard film on its surface.

Takeaway tip: To refresh a compact, take a knife and gently scrape the top, skimming off the film. "It's like exfoliation for your powder," says Rouleau.

Liner Notes

"With liquid eye liner, you can pick up bacteria from the eye and transfer it back to the tube," says Rouleau, who recommends pitching after three months (screwing the top on firmly and quickly after using can help prevent bacterial growth). Eye pencils have a built-in defense system: They have a wax-based formula, which prevents bacteria from growing, says Tanzi. These liners have a shelf life of up to two years.

Takeaway tip: Make sharpening a weekly ritual and tissue-off pencils you use at the water line after each use.

Red Eye

When it comes to mascara, make it a short and sweet affair—three to six months, max. "Eyelashes are there to protect your eyes and prevent contaminants from getting into them," says Rouleau. "So anything that's collected on your lashes—bacteria included—can hitch a ride back into the tube." Touching the mucus membrane with the wand, which is easy to do, compounds the problem.

Takeaway tip: Think that rapidly pumping an applicator will yield improved coverage? Nope, it may lead to an excess of mascara that can flake off and fall into eyes.

Sticky Business

Lipstick's waxy base allows you to keep it for two years—far longer than that "it" girl hue may last. Glosses, with their gel or liquid formulas are passé at nine months, but you could eke out 12 with regular alcohol swabbing. "The biggest worry is contracting a virus. If you share with a friend and they have the cold-sore virus, you can get it," warns Tanzi. "And if you've used one of your own lip products during an outbreak, the wand can spread the virus to another area of your lip."

Takeaway tip: The best advice for lipstick, gloss—or any cosmetics? Don't share. Ever.

Tool Time

Quality cosmetic brushes and sponges are makeup-application essentials, though they can only do their job properly if they're kept clean. "Use an antibacterial cleanser—I love Colorscience Pro's Brush Cleanser—to wash makeup sponges and brushes you use on your face and around your eyes every two weeks," says Rouleau. They can last for years if you treat them right.

Takeaway tip: In this case, a sunny windowsill comes in handy. "UV light kills bacteria so let them air-dry there for an extra bit of insurance," says Rouleau.

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