What to use and what to lose

Tossing that gunky bottle of lotion when it starts squirting out of the pump like water is a no-brainer.

But when should you throw out that 4-year-old shimmer powder that you use only for third dates and holidays? Should you toss it, too, even though you’re not even halfway through and it seems fine? And do you really need to toss your mascara after three months, even if you don’t wear it every day?

We consulted some experts to find out if and when cosmetics and other personal care products really should make their way from the bathroom counter to the wastebasket.

Yes, the experts said. But not always as quickly as the cosmetics counter would like you to believe.

“I think today the majority of products are made in very good controlled conditions,” said Jan Marini, president of Jan Marini Skin Research, base in San Jose, Calif. “They’re safe. You rarely hear of someone having an issue.”

Here’s a roundup of their best advice. These guidelines, they cautioned, apply only to products that have been stability tested (any reputable mass-market brand) and have preservatives added. Organics and personal care products without preservatives, they said, degrade much more quickly.

MASCARA

How long to keep it: Three to six months

Why: Your eyes are a haven for bacteria because they’re wet and warm, explains Justin Klabin, who designs and manufactures personal care products. “When you apply the mascara to your eyes and put it back in the container, you’re contaminating it a little every day,” he said.

LIQUID FOUNDATION

How long to keep it: one year

Why: If the foundation starts to smell fatty or the color or fragrance otherwise changes, toss it, said Damiana Zullo, director of product and packaging development for Bliss.

POWDER (foundation, eye shadow, blush, etc.)

How long to keep it: Up to three years

Why: “Powders have a long, long life,” Marini said. “Most powders don’t have water, so there are few microbials that will grow.”

EYE AND LIP LINER

How long to keep it: Indefinitely

Why: As long as you sharpen before use, you’re getting rid of impurities, Marini said.

LIPSTICK

How long to keep it: Two years or longer

Why: “It’s so apparent as soon as you take the top off and put it under your nose,” Zullo said. “If there’s a strong, waxy smell, get rid of it.”

OTHER WAYS TO KEEP YOUR PRODUCTS CLEAN AND SAFE

-Never add water to cosmetics. This makes a more welcoming environment for microbes and bacteria.

-If a product comes with an applicator wand or pad, make sure you sanitize it before each use. Otherwise, you’re shoveling in germs as you shovel out the product.

-Clean makeup brushes regularly with warm water and mild soap.

-Wash your hands before touching cosmetics.

-If a product changes in consistency, radically changes color or smells musty, moldy or at all differently, get rid of it. All are signs of bacterial growth.

-Don’t share makeup.

-Keep lids on when products aren’t in use. The more air that gets in, the more likely bacteria are to grow.

-Try to keep makeup and skin-care products out of warm, humid areas. If storing them in the bathroom, at least put them in a drawer.

Sources: Jan Marini, president of Jan Marini Skin Research; Damiana Zullo, director of product and packaging development for Bliss; Justin Klabin, personal-care-product designer and manufacturer