Does Sunscreen Really Expire?

The ingredients in SPF can break down, losing their effectiveness to filter or block ultraviolet light, says dermatologist Allison Arthur , MD, a board-certified dermatologist in Orlando, Florida.

Not only can using an old, expired formula be ineffective, but it also can result in a nasty sunburn. Heres everything else you need to know about how sunscreen expires so you can stay safe in the sun.

What's the typical shelf life of SPF?

Just like a carton of milk, skincare products have expiration dates. Before applying, double-check what the packaging says to ensure its still fresh. But beware: Some bottles may not have one listed.

If you buy a sunscreen that lacks an expiration date, it's helpful to write the purchase date on the product so you know how long you've had it, advises Dr. Arthur. Forgot to label it? A general rule of thumb is that if its over a year old, its time to replace it.

The year-rule should be applied to both chemical and physical sunscreens. According to Henry Lim, MD, a dermatologist in Detroit, Michigan, chemical formulations (ones with ingredients such as oxybenzone, avobenzone, and homosalate) will degrade over time due to oxidation, while physical protectants (such as zinc oxide or titanium dioxide) will begin to clump together, rendering them ineffective.

Another thing that could speed up your bottles retirement party is heat exposure. Extreme temperatures may lead to more rapid degradation of sunscreen, especially for chemical filters, says Dr. Arthur, so definitely dont apply an older bottle thats been stored in the trunk of a hot car or in a place that doesn't have AC.

What are the warning signs your sunscreen has expired?

Even if your sunscreen is technically not expired, there are a few tell-tale signs that its gone bad prematurely. The first thing to watch out for is any changes in texture. Its consistency should never look or feel different upon application. If the product becomes watery, grainy, or changes color, throw it away! says Dr. Arthur.

Another reason to send your SPF on a dumpster dive is if it has a funky smell.

Make sure you're fully protected.

While a quality sunscreen is the best way to stay safe in the sun-and if youre applying it daily, theres really no excuse to have an expired bottle on your hands-there are other things you can do to shield yourself. This is especially true if youre going to play sunburn roulette with an iffy bottle of SPF that may or may not be expired.

First, try to avoid the peak hours of sunshine, a.k.a. anytime from 10 a.m. to 4 p.m. UV exposure is greater during that time frame compared to earlier in the morning or later in the afternoon.

Remember that shade is your friend too, so plop down under a leafy tree, umbrella, or cabana whenever possible. Cover up with clothing, wide brimmed hats, and sunglasses, adds Dr. Arthur. I am a huge fan of sun protective clothes that use fabrics specifically designed to block UV rays.