We know it's a tough call throwing away your favorite blush or lipstick, but abiding by makeup expiration dates is actually incredibly important. Why? Cosmetics trap bacteria, which means replacing them regularly is necessary to avoid skin irritation, breakouts, eye infections, and styes. Not pretty, right? According to makeup artist Ashely Rebecca, "Skin irritations such as rashes, bumps, and burning sensations can occur when using expired products. If you use mascara or eyeliner that’s past its expiration date, you can experience swelling, itchiness, or redness. It’s always best to see a dermatologist immediately if you experience any kind of reaction." (And it's not just your makeup formulas—check out what happened when we tested bacteria levels on makeup brushes).

But here's a caveat: Unlike the contents of your fridge, the use-by date on your makeup products relies on the first day you use them, not the purchase date. "If you’re ever stuck wondering, all products have a small symbol that look like a jar with a number/letter on the inside, ex: 12M. This means, usually, that a product has a 12-month shelf life upon opening," says celebrity makeup artist Brittany Whitfield. "For makeup, I always follow what the time frame is in the symbol. The worst possible thing would be to use an old, oxidized foundation."

So how do you know when to toss that foundation or mascara? Separation or changes in texture along with foul smells are dead giveaways the product has gone bad.

While it's crucial to look out for those telltale signs, it's still helpful to get a general idea of how long each product is meant to last. Keep reading to learn the makeup expiration dates for every kind of cosmetic, from blush to eyeliner.

Elnora Turner / Byrdie

Face

Foundation

Charlotte Tilbury Magic Foundation $44 Shop

Shelf Life: Six months to one year

Maintenance Tips: Keep your foundation germ-free for longer by keeping your fingers away from the neck of the bottle. Instead, gently drip the formula onto the back of your hand before you apply. If you notice your foundation starting to separate, it’s definitely time to toss it.

"Products, where you dip your finger to apply on the skin, are more susceptible to bacterial contamination," says Margarita Lolis, MD, of Schweiger Dermatology Group says. "Lotions with a pump are generally safer and less likely to be contaminated. Products with less preservatives, such a those made for sensitive, have less preservatives and bacteria are more likely to grow."

Liquid Highlight

Benefit High Beam Liquid Highlighter $18 Shop

Shelf Life: Six months to one year

Maintenance Tips: While not as long-lasting as their powder counterparts, the liquid highlight can last up to one year. Store in a cool, dry place and opt for a disposable applicator when applicable to maximize its shelf life.

Concealer

Tarte Cosmetics Shape Tape Concealer $27 Shop

Shelf Life: Six months to one year

Maintenance Tips: Similar to foundation, concealer can last up to a year. Keep the product out of direct sunlight, avoid touching the application with your fingers, and when you notice separation it's time to toss.

Blush and Powder

MAC Cosmetics Powder Blush $25 Shop

Shelf Life: Two years

Maintenance Tips: The longest-lasting color cosmetics you’ll ever buy, powder-formula blushes last around two full years. "Ideally, from personal experience, powders can be extended for longer periods of time if you’re actively and regularly cleaning your brushes. Otherwise, you’re putting old makeup, germs, and skin cells into that powder product every time when your tools are dirty," says Whitfield. Always, always keep your brushes clean!

Cream Blush and Multiple Sticks

Clinique Chubby Stick Cheek Colour Balm $26 Shop

Shelf Life: 12 to 18 months

Maintenance Tips: Toss cream blush and “multiple” sticks (as in, products you can use on your cheeks and lips) if you notice a change in texture.

Always use clean hands when applying any product to help keep the tubes and pots germ-free.

Lips

Lipstick, Liner, and Gloss

Nars Lipstick $26 Shop

Shelf Life: One year

Maintenance Tips: It’s time to toss your favorite lip products when you notice a change in their texture—whether that means they dry out or they get goopy. Make your favorite red last longer by keeping it in a cool, dry place (not in your hot car).

Eyes

Brow Pencil and Kohl Eyeliner

Lancôme Le Crayon Khôl Smoky Eyeliner $26 Shop

Shelf Life: One year

Maintenance Tips: Pencils last longer than most eye products since they’re constantly being sharpened. Keep your liners away from your steamy bathroom to extend their life.

Mascara

Maybelline Volum' Express the Falsies Mascara $8 Shop

Shelf Life: Three months

Maintenance Tips: Replacing your mascara regularly is crucial for avoiding eye infections. Switch out every three months (or sooner if you notice the formula getting clumpy or starting to smell funny, signaling it’s gone bad). And, of course, don’t ever share mascara, as it can cause cross-contamination.

Liquid Eyeliner

Eyeko Line and Define Skinny Liquid Eyeliner $22 Shop

Shelf Life: Three to four months

Maintenance Tips: Just like mascara, don’t share your liquid eyeliner—germs are your biggest enemy with this type of beauty product.

The more moisture the product has—or the closer it comes to your eyes—the shorter its life span.

Eye Shadow

Anastasia Beverly Hills Eyeshadow Single $12 Shop

Shelf Life: Three to six months

Maintenance Tips: While powder shadows can last as long as powder blushes (about two years), they should be replaced more often since they’re used around your eyes.

Gel Eyeliner

Stila Cosmetics Smudge Pot $20 Shop

Shelf Life: Two months

Maintenance Tips: Unfortunately, a pot of gel eyeliner should only be used for a few months since it easily traps bacteria.

Fragrance

Chanel No. 5 Eau de Parfum $105 Shop

Shelf Life: Eight to 10 years

Maintenance Tips: Fragrance is the longest-lasting product in your beauty routine—by far! Max out your perfume’s shelf life by keeping your scents out of direct sunlight. (Some brands, like Le Labo, even suggest storing them in the fridge).

Nail Polish

JINsoon Nail Lacquer $18 Shop

Shelf Life: One to two years

Maintenance Tips: Heat and direct sunlight will make your polish separate and become discolored faster, so store your lacquers upright in a cool, dry place. There are also tricks to help you extend the life of polish that has gone goopy.