Ask the Expert: What Number SPF Do I Actually Need?

May 18, 2017
By: Jackie Burns Brisman | by L'Oréal
Ask the Expert: What Number SPF Do I Actually Need?

By now, we should all be aware that wearing sunscreen with broad-spectrum SPF is key in protecting skin from the effects of UV ray damage—everything from wrinkles, fine lines, and discoloration to skin cancers like melanoma. But, with so many sunscreens with varying levels of SPF protection—we’re talking SPF 4 to 100+—it can have a person wondering, “What number SPF should I use?” Well, keep reading.

Before we answer your burning question—or, we suppose, the question that will keep you from literally burning—first things first, let’s have a quick refresh. SPF stands for Sun Protection Factor. It is indicative of the amount of time you can spend outside before your skin begins to burn. For example, in theory, an SPF 15 would allow one to stay under the sun for 15 times as long as they would otherwise be able to without any sunscreen. A higher SPF number reveals that the sunscreen can filter out a greater number of UV rays—SPF 15 filters about 93 percent of UV radiation, while an SPF 30 would filter roughly 97 percent. Finally, when looking for an SPF, always, always, always seek out sunscreens labeled as broad-spectrum which means that it filters both UVA and UVB rays.

Now for the good stuff. How much do you actually need? For years it was recommended that you never leave the house without layering on SPF 15, but recently the American Academy of Dermatology—as well as all of our experts—advise that you up the number to SPF 30. That is, however, if you have skin that isn’t prone to burning. If your skin starts to get red soon after venturing outside, use an SPF 50-65. And, if your day in any way involves water sports or sweating—and this summer, really…who’s day doesn’t include sweat?—be sure your SPF is also water-resistant and you re-apply as directed.

Think that higher numbers of SPF are safer? Think again. Sometimes those excessively high numbers—read: SPF in the triple digits—give a false sense of security, leading you to think you don’t have to reapply as often as you need to.

That brings us to our next point. Once you have a great sunscreen with broad-spectrum SPF you need to make sure you use enough—about 1 full shot glass full—and reapply often—at least every two hours. When you apply is another important factor to consider. Chemical sunscreens must be applied at least 20-30 minutes before venturing into the sunlight, whereas physical sunscreens—those formulated with zinc and titanium dioxide—work right away. 

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Up your protection factor by wearing sun-protective clothing (think hats, sunglasses, and long sleeves) and seeking shade anytime you’re spending lots of time outdoors. 

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