If you’re hitting the beach for vacation this summer (or just getting away one Saturday), you’re going to need some serious SPF to prevent sunburns. But before you reach for that bottle of sunblock from last summer, you might want to consider the facts – old sunscreen isn’t safe.

“Using an expired sunscreen can lead to reduced protection from UV rays due to diminished SPF,” Holly Thaggard, founder and CEO of Supergoop!, told Birchbox. Not to mention – old products often harbor bacteria and fungus because they’ve been sitting around for so long after being used.

The active ingredients in sunscreen also break down in high temperatures, so even if your stash is new, it might lose its effectiveness if you keep it in the car or leave it in the sun at the beach.

The solution? Keep something like COOLA – SPF 30 Face Classic Moisturizing Sunscreen Cucumber in your purse for daily use, then take a fresh bottle of PETER THOMAS ROTH – Max Sheer All Day Moisture Defense Lotion SPF 30 to the beach in an opaque beach bag.