By now, the skin-care commandment that says you should be wearing sunscreen every single day is so ingrained in my brain that I practically apply it every morning with my eyes closed. I don’t even think twice about it—I simply grab whatever SPF is nearest to me and swipe it all over my face. But, as I grabbed whatever was leftover from summer 2018, something I forget to pay attention to is the fact that sunscreen can expire. Oops.

“Sunscreens are classified as an ‘over-the-counter drug’ (OTC), and because of this, the FDA requires that they have an expiration date,” says Loretta Ciraldo, MD, FAAD, dermatologist and founder of Dr. Loretta Skincare. And that expiration date depends on a couple of factors including the formula and the product packaging, according to Sofia Gracia, director of product development at Supergoop!

“[An SPF’s shelf life is dictated by] the formula itself, or how well a product is formulated, stabilized, and how effective its preservative system is; the packaging, including how compatible the materials are with the formula and how well they protect it from the environment during storage and use; and the raw materials—for instance, natural ingredients like oils, butters, and extracts have a shorter shelf life and are also much more sensitive to light and air exposure,” says Gracia.

“Sunscreens are classified as an ‘over-the-counter drug’ (OTC), and because of this, the FDA requires that they have an expiration date.” —Dr. Loretta Ciraldo

Whichever sunscreen you’re dealing with, whether mineral or chemical, tends to have an expiration date that’s no further than three years out from the date it was manufactured. “Regardless of the SPF actives used in a product, the FDA doesn’t allow more than a three-year expiration date from the day of manufacture,” says Dr. Ciraldo. “And all manufacturers make formulas to comply with this, since SPFs are OTC drugs.” Since that date comes from the moment it comes off the manufacturing line, it’s smart to simply expect that your SPF will be good for a year from when you get it.

Most of the time, you’ll be able to see the sunscreen’s expiration date clearly on the product…but this isn’t always the case, and if it’s not, write the date on the package so that you can remember to ditch it. “It’s best to purchase SPF products that have the expiration date clearly marked,” says Dr. Ciraldo. “If you have some SPF and aren’t sure how old it is, look for the expiration date stamped on it and discard if it’s past the date since it loses its effectiveness after that.”

So it’s very important to pay attention to, considering how strongly the sun’s rays can impact how well your skin is protected. If you’re not seeing the expiration date clearly on your SPF, Dr. Ciraldo and Gracia advise to mark the date of purchase on a piece of tape that you stick on the product, then stop using it between 6 to 18 months. “Allow for the fact that the product may have been manufactured up to six months before you bought it,” she says.

Also, in the case that your product doesn’t show a date on it, Gracia says there are tell-tale signs you can watch out for that can indicate it’s expired. “If the formula’s no longer uniform in texture is one warning sign,” she says. “For example, when squeezing a lotion out of a tube, you may notice there’s an oily substance that comes out separately.” This isn’t good.

Then there’s the scent: “If a formula doesn’t smell like it typically does, there might be an issue with it,” she says. “It’s also important to note that there’s going to be some variance in smell when using natural aromatic extracts. That being said, it should never smell rancid.” If you’re dealing with any of these signs, it doesn’t always mean the sunscreen actives aren’t effective—according to Gracia, it does mean that “the delivery system has been compromised, which signals that the actives won’t be delivered in a uniform layer to provide adequate protection, or that the preservative system is no longer working to stop contamination like mold, yeast, or bacteria.”

Really though, it shouldn’t be a problem—considering you apply SPF every day and a lot of it (right?!). “If you’re applying it every single day, you will rarely have to worry about not using a product up before it expires,” says Gracia. Good point.

BTW, here are the best moisturizing sunscreens to wear all year round. And *this* is how much sunscreen you should be using on your face, according to dermatologists.