Is SPF 30 Sunscreen Really More Effective Than SPF 15?

The myth: SPF 30 sunscreen is far more effective than SPF 15. True or false? Mike Dawson has the answer.

Wearing sunscreen can help stave off burns, premature aging, and skin cancer. You know this. But what you may not know is that the whole sunscreen-labeling system was established way back in 1978. And even after some milquetoast tweaks by the FDA this year, it remains confusing and kind of bullshit—and may give you a false sense of security while you bake in the sun.

Of course, you'd think a sunscreen with SPF 30 would be twice as strong as one with SPF 15, right? It isn't. An SPF 15 blocks 93 percent of UVB rays (the cause of those skin-slapping red burns); SPF 30 blocks only 97. And SPF 50 blocks just 98 percent of UVB rays.

But UVB rays are only half the problem. There are also UVAs, which drive much deeper into your skin, causing wrinkles and increasing your risk of cancer. (Exposure to both types of rays simultaneously and unprotected can increase that risk even more.)

Many U.S. sunblock brands say "Broad-Spectrum Protection" on the bottle. But according to the FDA, a product need have only a "certain percentage" of UVA protection to make that claim on the packaging.

Is this indefinite quantity of protection enough? Not likely, says the independent research-advocacy organization Environmental Working Group, which annually tests all sunscreens on the market. In fact, according to its findings, more than half the brands currently sold in the U.S. would be illegal in Europe due to their their lack of UVA protection. (Europe has far stiffer—and less confusing—guidelines for sun protection and lotion labeling.)

So, what should you do to combat both types of rays, without sacrificing that sun-kissed glow altogether?

First, using an SPF 15 sunscreen is adequate, though you will get slightly more protection from an SPF 30. Either way, choose a brand that contains either mexoryl or zinc oxide, two ingredients that have been shown to work best against UVAs. And finally, when you hit the beach, be sure to apply a shot-glass-size amount every 40 minutes—even if your lotion is supposedly water- or sweat-proof.

Don't even get us started on that claim...

— Dawson is a magazine writer and editor and a regular contributor to Details.

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