Throw out your pre-pandemic makeup – it could give you an eye infection or a rash

• It's time to throw out any mascara you've had for six months or more.
• Liquid makeup can grow bacteria, so be careful about what you put near your eyes.
• Powders and lipsticks typically last between a year and two.
• Visit Insider's homepage for more stories.

The pandemic has been going on longer than the lifespan of most makeup products.

That means if you're digging up old eyeliners and lipsticks from a makeup bag circa 2019, it's probably time to toss them.

Most cosmetics last between six months and a year, but it's not unusual to keep them for longer. Whether or not you should use old makeup depends on the product and how you store it.

Two symbols tell you how long to keep makeup

The open cream jar icon, also known as the "Period After Opening" symbol, contains the number of months a product lasts once opened. Most products are marked "6M," "12M," or "24M" to correspond with their shelf life.

Some makeup may also be stamped with a batch code, which tells you when the product expires regardless of opening.

The numbers won't make sense to an untrained eye, but websites like Cosmetic Calculator - which went viral on TikTok last year - can help decode them.

If you can't find these symbols on the makeup products, they were likely listed on the packaging. If the packaging is long gone and you can't remember when you bought it, it's probably time to throw out that product.

Be extra careful about what you put near your eyes

If you're going to get rid of any crusty cosmetics, the first thing to throw out is mascara and other liquid eye makeup that you've had for six months or more.

Putting potentially pathogen-ridden products near your eyes could lead you to develop conjunctivitis or worse.

"It's always better to be safe than sorry when it comes to products around your eyes," Elisabeth Anderson, director of science communication for the Center for Research on Ingredient Safety at Michigan State University, told Insider.

Powdered eyeshadows and eyeliner pencils typically have a bit more leeway than liquid products, with shelf lives ranging from one to two years.

Liquid makeup is more likely to develop bacteria, mold, or yeast compared to dry powders.

Lipsticks and powders have longer shelf lives

Anderson said she's been using a years-old blush without a problem.

"Risking a slight rash or irritation on your face is a totally different ballgame than a serious eye infection," she said.

Lipstick also has a longer shelf life than you might expect. POAs range between a year and two, depending on the product.

That's because your mouth is better prepared to fend off harmful bacteria compared to your eyes and skin, Anderson said.

You should still check out the texture and odor of lipsticks and powders before using them. Any clumping, separation, or funky smells indicate it's time to trash it, or risk a bacterial or fungal infection.

'All-natural' cosmetics likely have a shorter lifespan

Preservatives are typically in makeup for a reason: to keep it from going bad.

Some more natural ingredients can be used to replace preservatives, but Anderson said they may end up being harsher on your skin.

"I personally would never put something that didn't have some science behind it near my eyeballs," Anderson said.

If you buy preservative-free makeup - or anything marketed as "all-natural" that doesn't have a clear ingredients label - you should treat it like food, Anderson said. Keep it in the fridge, and throw it out sooner than you would other products.

Your makeup will last longer if you store it in the right place

Anderson said too many people keep their makeup in the bathroom, which is a humid place where germs could thrive.

Makeup kept in a cool, dry place will hold up for longer than improperly stored cosmetics. Make sure to close the containers tightly to ensure bacteria and dust don't get in.