Does sunscreen actually expire? The truth, according to experts

Safe to say that we’re all well-versed in basic sunscreen commandments. Thou shall use broad-spectrum SPF 30 protection every day. And reapply said sunscreen every two hours. But something that often gets ignored when it comes to safe skincare practices is that tiny little label on the sunscreen bottle known as the expiry date.

It’s natural to not want to waste any product, especially if you can’t physically see anything wrong with it. But using sunscreen—or any skincare product in general—past its shelf life can come with some major consequences. Below the experts break down why everyone should take a sunscreen’s expiry date seriously and how to get the most out of your favorite sunscreens before it’s time to toss them out.

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Is there a sunscreen expiry date?

To put it bluntly: yes. There will come a time when even the best sunscreens are no longer effective. According to Krupa Koestline, founder and chief cosmetic chemist at KKT Labs, sunscreens are considered over-the-counter drugs with specific testing guidelines that they have to follow and adhere to. All sunscreens, Koestline says, are required to have expiry dates listed to enter the market and the sunscreen itself has to work up until that specified date.

If there isn’t an expiry date listed, the U.S. Food and Drug Administration (FDA) says that the manufacturer must prove that the product can remain stable for three years. Then it can be considered expired three years after the date of purchase.

Expiration dates may differ based on formulation. Hadley King, MD, a New York City-based board-certified dermatologist, says that the formula for physical sunscreens (a.k.a. mineral sunscreens) are considered more stable than chemical sunscreens, and thus have longer shelf lives. She explains that physical sunscreens that include ingredients such as zinc oxide and titanium dioxide won’t change their molecular structure when exposed to light and keep ingredients stable longer than those found in chemical sunscreens, which consist of more unstable molecules and can oxidize over time.

When sunscreens expire can even differ based on the type you choose. King says a powder sunscreen contains minerals that are more stable and longer lasting while liquid formulations will be less stable. But you can expect sunscreens in general to last anywhere between two to three years.

What happens when you use expired sunscreen?

The main downside to using expired sunscreen is that you won’t get adequate sun protection from the sun’s harmful UV rays, which can lead to signs of premature aging and more dangerous skin and health concerns, such as sunburn and skin cancer. “Expiration dates indicate the day beyond which sunscreen is no longer effective,” says Koestline. “You risk getting sunburns when using an expired sunscreen as the protection is no longer guaranteed.”

She goes on to explain that sunscreen formulas work so that UV filters are applied evenly over your skin. Once that sunscreen has hit its expiry date, the formula will begin to separate and those active ingredients that filter out the UV rays may end up clustering in one area upon application.

King adds that expired sunscreen could potentially irritate the skin. Ingredients could have broken down into irritating chemicals once past their expiration date or there could be bacteria and yeast growing in the product, which could lead to infection and forms of skin irritation such as bumps and rashes.

Both experts and the FDA strongly advise using expired sunscreen and tossing it all together. If there is a chance where you have no other option for sun protection, King says that using it might be okay if it’s only slightly past the expiration date and if the sunscreen looks, feels, and smells normal. Just do a test patch first to make sure you don’t react badly to it and still have a plan to replace it with new sunscreen ASAP.

“Expiration dates are stamped on sunscreen containers to specify the time limit for the product’s stability and efficacy,” emphasizes King. “For optimal sun protection as well as texture, stability and sterility, use sunscreen prior to the expiration date.”

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How can you tell if your sunscreen has expired?

The easiest way to tell if your sunscreen has expired is by looking at the label. But if there isn’t a specific expiration date listed, King says that you can assume it’s good for three years past its purchase date, just as the FDA advises.

Other signs that point to sunscreen being past its prime are changes in color, consistency, smell, and texture. Even if this occurs before the expiration date, it’s most likely no longer safe to use and you’re better off grabbing a new one.

How do you properly store sunscreen?

Just like you would with any other skincare product, the best way to prolong the shelf life of your sunscreen is to store it properly. Both Koestline and King say that you’ll want to put sunscreen away from direct light as the sun can cause some formulations to break down and separate before the expiration date. Koestline says to keep products in a place that’s dry and at room temperature at a minimum. For best results, King says to opt for a cool, dark place.

This story was originally published on Vogue.com.