Some sunscreens have an expiration date on the container, which makes it easy to determine the product’s “freshness.” (You may have to do a little searching—the dates aren’t always easy to spot.) “A sunscreen that expires in six months should work as well as one that has an expiration date of three years away,” Booth says.
But the FDA doesn’t require manufacturers to date their products. If you have a date-less sunscreen and can’t recall when you bought it, don’t take a chance. Buy a new one and use a permanent marker to write the date you purchased it on the container.
And regardless of the sunscreen’s expiration or purchase date, toss it if the contents have separated—“spoiled” sunscreen will be watery—or if it has changed color or has a funny smell.