Can I use last year’s sunscreen? A cosmetic chemist explains
And since SPF is strictly regulated by the FDA, it must have an FDA-approved expiration date on it. “The Food and Drug Administration requires expiration dates on sunscreen,” agrees Robinson.
If your bottle doesn’t have an expiration date on it (or maybe it’s frayed from wear or sweat), he recommends writing the purchase date on the bottle yourself. Most sunscreens usually have a shelf life of around three years, so keep track of when you bought and opened the bottle.
So if you bought last year’s sunscreen last year, you should be fine If it’s a four-year-old bottle, it’s probably time to throw it away.
But! Your sunscreen can expire much earlier than the suggested expiration date if you don’t store it properly. “Sunscreen should be stored in cool dark place1 to maintain its stability and effectiveness,” explains Robinson, because direct sunlight and heat can break down its molecules that protect against UV rays.
This means that if you often leave your sunscreen in a hot car or outside by the pool, you could end up with rancid SPF sooner than you think.
How do you know if your sunscreen has gone bad? Check the texture and color of the slime: Expired sunscreens tend to flake or appear lumpy, or they may have a yellow or brown tint due to oxidation. If your SPF has a pungent smell, that’s also a sure sign that it’s gone rancid (and probably infected with bacteria). You can read more about sunscreen best practices here, including how to store different bottles.