We’re all guilty of hoarding some type of beauty product, unable to toss the nearly empty or rarely used containers because 1) we just might get around to using them again or 2) they were way too expensive to toss already. My secret stash is full of bold shades of lip gloss and eyeshadow that I swear I’ll try one day. But how long is too long to keep those old products around? And will they still be any good when I finally go to swipe them on?

An unopened product can sit on store shelves for months or even years before it goes bad, but once you’ve opened the compact or bottle, the clock starts ticking on the life of the ingredients. “Products have specific dates of expiration based on when the actives and the preservatives in them are no longer potent,” explains dermatologist Michael Gold, M.D., founder of the Gold Skincare Center in Nashville, TN. When actives go bad, cosmetics simply lose their efficacy, but when the preservatives that keep the formulas from becoming contaminated expire, “you may be using products that have the potential for increased skin irritation or even infection,” according to Gold.

Some signs that the old items in your stash are starting to turn include changes in color and texture—an old foundation may go on less evenly or take on a chalky consistency, for example. Other items, in particular mascara, may start to smell funny. And increased skin irritation is of course a sure sign that something should be tossed.

Looking for more specific rules on when to get rid of your old products and start shopping for new stuff? Check out our guidelines on when to toss various items.

Every Three Months

Mascara: It’s dark and wet inside that mascara tube: the perfect breeding ground for bacteria. Avoid pumping your wand in and out of the tube, which adds air to the mix, and get rid of your tube as the seasons change.
Liquid eyeliner: Liquid liner tubes can also harbor bacteria so they should be tossed more frequently. Pencil liners, on the other hand, can last for several years, as you only need to sharpen them to reveal a clean surface (just be sure to sanitize your sharpener with alcohol often).

Every Six Months

Jarred skincare products: Every time you touch a cream with your fingers, you’re adding germs to the jar. Lotions in a pump container last longer as there’s less chance for contamination.
Liquid foundation: These products often contain water so they go bad more quickly as the liquid evaporates. You can also run into contamination issues every time you put your hands, makeup sponge or foundation brush to the bottle.
Sunscreen: As an FDA-regulated product, sunscreen usually comes with an expiration date that’s about a year out from when you probably purchased the product. Once a sunscreen is opened, though, the formula can become unstable as it is exposed to light and air. An unstable formula means your skin isn’t getting the full potency of protection that you purchased, so to play it safe you should replace your bottle every summer or after six months.

Every Year

Shampoo and body wash: When water gets into products you keep in the shower, it can break down their formulas so they’re less effective. Keep lids on tight and toss the bottles every year if you haven’t used them up by then.

Every Two Years

Powder-based eye shadow, blush and foundation: Bacteria can’t grow where there’s little to no water, which is usually the case with powder cosmetics. Botanical-based powders, though, may contain trace amounts of plant oils that will evaporate over time. If a product feels chalky and doesn’t blend into skin as easily, you may need to replace it sooner.
Lipstick: The texture will most likely change well before the product actually goes bad. When a lipstick is less creamy and dries out lips, the moisturizing ingredients have likely evaporated and it’s time to replace the tube.
Nail Polish: A polish’s consistency will change over time, becoming dry and gooey. Try not to store bottles in the bathroom as heat and humidity can speed up this process.

Megan O'Neill is Beauty Editor at EndlessBeauty.com.