Why Your Sunscreen Should Be SPF 100

Photo: Romano Cagnoni/Getty Images

What kind of health nut wears SPF 100 sunscreen? You, probably soon.

A recent study in the Journal of the American Academy of Dermatology might turn everything we thought we knew about sunscreen on its head. The study found that wearing SPF 50 sunscreen leads to significantly more sun-induced skin damage than SPF 100+. While this may sound like common sense, the study bucks industry-wide lore that sunscreens higher than SPF 50 offer nominal additional protection. For decades, SPF 100 sunscreens were pegged as crafty marketing ploys. Confused? Here’s a guide from the Cut.

So, why should I even care about sunscreen?

Sorry …
Fine. Sunscreen protects your skin from harmful ultraviolet (UV) sun rays. UV rays are divided into three groups: UVA, UVB, and UVC. UVC rays don’t travel past the Earth’s atmosphere and are irrelevant in the context of sunscreen. UVA ray exposure mostly leads to signs of premature aging, like wrinkles and sun spots, while UVB rays cause sunburns. Both UVA and UVB rays can cause skin cancer.

Okay, how do sunscreens work?
Most sunscreens offer a combination of mineral and chemical protection. Mineral ingredients like zinc oxide “block” sun rays from reaching your skin, while chemical sunscreen ingredients, like oxybenzone, absorb sun rays, so your skin doesn’t have to.

How does SPF relate to sunscreen?
Sun Protection Factor (SPF) measures how effectively sunscreens protect skin. There are two ways to think about this. One way compares how unprotected (sunscreen-free) skin reacts to sun exposure versus protected skin. Let’s look at SPF 30. It will take your skin 30 times longer to experience the same sun-exposure effects you would notice if you were to wear nothing at all. So if you normally burn after ten minutes in the sun without sunscreen, you will burn after 300 minutes (5 hours) in the sun with SPF 30.

Another way to consider this is is in terms of how many sun rays will hit your skin. SPF 15 prevents 93 percent of UVB rays from reaching your skin. SPF 30 stops 97 percent of UVB rays, SPF 50 keeps out 98 percent, and SPF 100 keeps out 99 percent. “It doesn’t sound like much of a difference, but if you look at it the other way, you’re getting twice the exposure with the 50 than with the 100,” Darrell Rigel, a dermatologist and co-author of the new SPF study, explains. “Cumulatively over time, that adds up. The analogy I give is: there are two taxis. In one taxi the meter is going twice as fast,” he says. “Over time, you’re going to damage your skin twice as fast.”

So what does the new sunscreen study say?
The study looked at 199 men and women. Doctors treated one half of the participants’ faces with SPF 50+, and the other half with SPF 100+. After about six hours of sun exposure, 110 participants were sunburned on their SPF 50 side, and ten were sunburned on the SPF 100 side. “We found that you had about 11 times the chance of burning on the SPF 50 side of your face versus the SPF 100 side of your face,” says Rigel. “It was statistically and clinically significant.”

Oh! And out of curiosity, what prompted this study?
“In 2011, the FDA came out with a bunch of new ruling proposals on sunscreens,” says Rigel. “The FDA proposed putting a cap on sunscreens over SPF 50 when it came to labeling, so anything over 50 would be labeled simply as 50+. The basis of that was the belief that there’s really not a big difference.” But now we know there is.

Why does it matter if there are SPF caps?
The biggest reason is that brands won’t make sunscreens higher than SPF 51 if they can get away with the same labeling treatment as SPF 100. In other words, there’s no economic incentive for them to invest in higher-SPF technology. This translates to weaker sun protection for you. And here’s something else to consider: Half of the world’s countries already have SPF labeling caps.

So did this study change the FDA’s mind?
“Based on our understanding, the FDA is not going to put a cap on SPF 50+ on sunscreens,” says Rigel.

Got it. So what does this study mean for me?
Am I talking to myself? Wear sunscreen! The higher the SPF, the better!

Forget SPF 30. Here’s Why Your Sunscreen Should Be SPF 100.