Not Sure If Last Year's SPF Has Expired? Read This First

Good news: you have a beach day planned. Bad news: the only sunscreen you can find is one sand-coated bottle that might be from last year . . . or the year before. While we absolutely condone product hoarding, sun protection is one beauty area you just have to take seriously. We talked to the experts to find out just how long you can stretch that SPF. Ask yourself these questions before using that sunscreen bottle from the back of the closet:

"All sunscreens are designed to remain at original strength for three years," says Dr. Paul Jarrod Frank of NYC Fifth Avenue Dermatology Surgery and Laser Center. If you had your sunscreen during Juan Pablo's season on The Bachelor, it's time for a new bottle. Pro tip: next time you bring home a fresh tube, write the purchase date on the lid with a permanent marker so you know exactly when to toss.

Any lumps or bumps in creamy sunscreen could mean the active ingredients are beginning to break down and become less effective. "Micronized zinc oxide and titanium dioxide, the two main ingredients in sunscreen, can clump together over time," explains Dr. Hadley King, dermatologist at Skinney Medspa. If you want an SPF with a longer shelf life, check the label for dimethicone or silica, additives that will keep your lotion stable and smooth.

When a liquid separates out from your cream, it means the ingredients have broken down and it's time for a new bottle. "Keep an eye out for white cream turning into a yellow liquid," warns Dr. Marina Peredo of Skinfluence Medical NYC.

As convenient as it seems to leave your sunscreen on the patio or in the trunk of your car, heat and sun exposure will eventually cause the active ingredients in SPF to break down. Keep product fresh by leaving it in a cool, dry place.

Sunscreen will still be effective — albeit less so — after three years, clarifies Dr. Peredo. But using the formula with deteriorating chemicals means that "you could develop a contact allergy, even though it's not necessarily harmful." If you are pinching pennies and don't want to buy a new bottle, spot-test a small area of your skin to test your reaction first.

Whether you're using a new tube or a bottle that was in your stash when Taylor Swift had long hair, apply responsibly. Dr. Peredo notes that true sun care means we shouldn't have to worry about SPF expiring, because we're using it religiously. "When outdoors, apply one tablespoon of sun protection every two hours," she advises. "Then there's no way a bottle should last more than one season — maybe two."