Sunscreen expires, and you can usually tell by checking the printed expiration date, looking for physical changes like separation or clumping, or counting back from when you bought it. The FDA requires sunscreen to stay effective for at least three years, so even bottles without a printed date have a reliable window if you track when you purchased them.
Check the Expiration Date First
The simplest method: look for a date stamped on the bottle or tube, typically on the bottom or crimped end. FDA regulations require sunscreen manufacturers to print an expiration date unless their stability testing proves the product remains effective for at least three years. If you see a date and it has passed, toss it.
If there’s no expiration date printed anywhere, the manufacturer has certified the formula stays stable for three years from production. The Mayo Clinic recommends writing the purchase date on the bottle so you have a reference point. Once three years have passed since that date, throw it out.
Look for the Open-Jar Symbol
Many sunscreens, especially those sold internationally, carry a small icon on the back label that looks like an open jar with a number inside, such as “12M” or “24M.” This is the Period After Opening (PAO) symbol, and it tells you how many months the product stays good after you first open it. A “12M” label means 12 months of use from the day you cracked the seal. This timeline can be shorter than the three-year shelf life, so it’s worth checking both.
Physical Signs Your Sunscreen Has Gone Bad
Even before an expiration date arrives, sunscreen can degrade if it’s been stored poorly or contaminated. Here are the clearest signs:
- Separation: The formula looks oily on top and watery underneath, or the ingredients have visibly split apart. A stable sunscreen should be uniform.
- Clumping or graininess: If the product comes out in lumps or feels gritty rather than smooth, the active ingredients have likely broken down.
- Watery or runny texture: A consistency noticeably thinner than when you first bought it suggests the emulsion has destabilized.
- Unusual smell: Bacterial growth can give sunscreen an off or sour odor that wasn’t there originally.
- Color changes: Yellowing or darkening of a product that was originally white or clear is another red flag.
Any one of these signs is reason enough to replace the bottle, regardless of what the printed date says.
Why Expired Sunscreen Is Risky
The most obvious problem is reduced UV protection. When active ingredients break down, the SPF rating on the label no longer reflects what the product actually delivers to your skin. You could apply it generously, follow all the right steps, and still burn.
But there’s a less obvious risk too. Chemical sunscreens that have been oxidized, meaning exposed to air for too long, can cause an allergic skin rash that looks like a blistering sunburn. So rather than just failing to protect you, a degraded product can actively irritate your skin.
Chemical vs. Mineral Sunscreen Shelf Life
Chemical sunscreens work by absorbing UV rays and converting them into heat through a chemical reaction. That process changes the molecular structure of the active ingredients over time, which is one reason these formulas can lose potency as they age. Mineral sunscreens use zinc oxide or titanium dioxide to physically reflect UV light off the skin. These minerals are inherently more stable compounds, though the overall product can still degrade if the cream or lotion base breaks down.
Both types should be replaced after the expiration date or the three-year mark. The difference in stability between the two isn’t large enough to justify stretching timelines for either one.
How to Store Sunscreen So It Lasts
Heat is the most common concern, but it may matter less than people assume. A study that exposed sunscreens with SPF 30 and 50 to real vehicle cabin temperatures, including over 378 hours above 100°F, found no meaningful degradation of the active ingredients. So leaving a bottle in your car on a hot day isn’t an automatic death sentence for the product.
That said, keeping sunscreen in a cool, dry place is still the safest bet for long-term storage. More important than temperature control is keeping the product clean. Wash your hands before applying, and close the lid tightly after every use. This limits oxygen exposure, which causes oxidation, and prevents bacteria from transferring into the bottle. Both of those factors break sunscreen down faster than moderate heat does.
Decoding Batch Codes Without an Expiration Date
Some bottles have a batch code or lot number but no readable expiration date. Many manufacturers use a format called a Julian date code, which looks like a five-digit number. The first two digits represent the year, and the last three represent the day of that year. For example, a code reading “22150” would mean the 150th day of 2022, which is May 30. From that manufacturing date, you can count forward three years to estimate when the product expires.
Not every brand uses this format, and some batch codes are proprietary. If you can’t decode the number, many manufacturers will look up your batch code if you contact their customer service line. But the simplest backup method remains writing the purchase date directly on the bottle with a permanent marker.