I was pretty proud of my extensive sunscreen collection until I started wondering if I just had a ton of expired sunscreen on my hands. (Not literally, but you know.) I don’t mean the moisturizer with SPF I wear every day. Naturally I go through that stuff quickly. No, I mean the bevy of sunscreen options with higher SPF I had stashed away specifically for skiing and going to the beach, which I only do a few days a year, plus some physical sunscreens I use sporadically to protect any new scars. Unfortunately, in the process of reporting this story I learned that only two of the seven sunscreens in my stockpile were actually usable.
Just as you shouldn’t take expired medication, you shouldn’t use expired sunscreen. “A sunscreen is an over-the-counter drug—a medicine—and it should be viewed as such,” cosmetic chemist Konstantinos Lahanas, Ph.D., founder of the cosmetic science research company the Lahanas Group, LLC, tells SELF.
The weird thing is that some sunscreen bottles don’t come with expiration dates. Even if yours does, the date can become basically illegible over time. So why should you buy a new bottle of sunscreen if yours is expired, and how can you tell it’s too old if you’re not sure? Here, experts answer those questions and more.
Here's why sunscreen expiration dates exist and how they work.
The chemicals in any kind of sunscreen break down over long periods of time, eventually becoming less potent, John G. Zampella, M.D., instructor in the Ronald O. Perelman Department of Dermatology at NYU Langone Health, tells SELF. Dr. Zampella has a pretty sweet analogy to drive home this point.
“Think about those week-old strawberries in your refrigerator. After being in the fridge for so long, they start to decay,” he says. “At first, you might still recognize them as strawberries, but eventually, they become covered in mold and don't even look like strawberries anymore.”
It’s a similar story with your sunscreen, he explains: “Eventually, just like your strawberries, all of those compounds break down, and the sunscreen becomes useless.”
That’s where expiration dates come in (on the bottles that have them, anyway). All drug manufacturers (including the ones who make sunscreen) have to perform stability testing before they can sell their products, the U.S. Food and Drug Administration (FDA) explains. Based on that testing, they can submit a drug application with a proposed expiration date and usage instructions so you don’t accidentally spoil your sunscreen before that date arrives.
The FDA recommends drug manufacturers follow standardized guidelines for stability testing, like those outlined by the International Council for Harmonization. The guidelines are full of complicated technical terms and scientific hurdles for manufacturers to clear. To sum it up, these recommendations essentially ask that manufacturers expose at least three batches of the product to multiple storage conditions over the course of months or years. Then manufacturers are supposed to conduct all sorts of tests—physical, chemical, microbiological, etc.—to figure out how long their drugs will reliably stay safe and effective under different conditions over time. (There’s flexibility in these recommendations, but that’s the gist.)
So behind that tiny expiration date on your sunscreen bottle is a lot of scientific effort to make sure the drug will be as effective as possible up to that point—but not after. This is why the FDA and American Academy of Dermatology (AAD) both recommend tossing your sunscreen as soon as it reaches its expiration date.
OK, but what happens if you do use expired sunscreen?
Honestly, it’s anyone’s guess, and that’s why you probably just shouldn’t. “If you use sunscreen after the expiration date, it might still have some UV-blocking power, but it won't be the full strength that's listed on the label,” Dr. Zampella says. Even sunscreen with a high SPF like 75 can’t reliably protect you once it’s expired, he adds. You can’t know if its post-expiration SPF has dropped to 70 or, say, 5 unless you happen to have a chemical laboratory in your home that you can use to analyze the product, in which case, cool and can we come over?
“Sunscreen does not have a time bomb embedded within that will [immediately] render it useless” once it expires, Lahanas says. But since there’s no way to know how much (if any) of its SPF has stuck around past its expiration date, any expired sunscreen should be considered ineffective, Lahanas says.
What if your sunscreen doesn’t have an expiration date?
Sunscreens that aren’t labeled with expiration dates have been proven to stay stable for at least three years, the FDA says. So any sunscreen without a listed expiration date “should be considered expired” three years after purchase, the FDA says.
One interesting point here is that your sunscreen could have been sitting on the shelf for a while before you bought it, so by the time it’s hit three years in your possession, it will have been more than three years since it was manufactured and the stability countdown clock began. But all sunscreens without an expiration date have been proven effective for at least three years—not exactly three years—so its time on the shelf won’t necessarily impact its efficacy. Obviously, this depends on how long the specific sunscreen was found to be effective and how long it was sitting on the shelf, but it’s not enough of a concern to make the FDA change its recommendation to consider sunscreen without an expiration date expired three years after purchase.
Basically if you find a sunscreen container in the bottom of your beach bag without an expiration date and you have zero idea when you bought it, you might as well toss it.
“Like with any other medicine, if you’re in doubt throw it out,” Lahanas says.
The same goes if your sunscreen hasn’t reached its labeled expiration date or you bought it more recently than three years ago, but its color or consistency has changed in a funky way, the AAD adds. That can be a sign that it's no longer safe to use. Sometimes that can happen earlier than expected if you store your sunscreen in a way that makes it degrade faster than usual.
Per the FDA’s guidelines, you should stash sunscreen at room temperature to keep the chemicals stable for as long as possible. That’s a tough ask if you’re taking sunscreen to a setting like the beach so you can dutifully reapply it. (Good job, by the way.) In that case, the FDA recommends wrapping the sunscreen container in a towel or throwing it into your cooler if you have one. Along the same lines, you shouldn’t store sunscreen in your car, where it can overheat.
If you buy sunscreen that doesn’t have an expiration date, the AAD recommends writing your purchase date on the container. That will help you have a better idea of when its time has come. (Even if your sunscreen does have an expiration date, you might want to write the date over again just in case the original one wears off.)
Finally, if you hate the idea of buying sunscreen without an expiration date because you don’t know how much its time on the shelf could be cutting into that three-year stability guarantee, you could stick with sunscreens that have listed expiration dates or buy new sunscreen much more frequently than once every three years, like once a year right before summertime when you need maximum protection from the sun.
So you don’t need to buy new sunscreen every year, but you probably should.
Dermatologists often say that you really should be using enough sunscreen that it doesn’t have time to go bad. It’s a common derm refrain: If it takes you fooorever to get through a bottle of sunscreen (like if you only make your way through one bottle all summer), you’re probably not using enough.
Granted, this type of thing is somewhat dependent on your habits, like if you prefer to spend every weekend in the company of some blessed air conditioning instead of frolicking in some waves or otherwise spending a lot of time outdoors. Overall, though, it definitely wouldn’t hurt to be so diligent about applying your sunscreen the right way and often enough that you never even have to worry about it expiring.
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Originally Appeared on Self