Does sunscreen save skin — or damage it?

By Laurel Naversen Geraghty

updated 9:35 a.m. ET Feb. 5, 2009

I was no different from most college students: During spring breaks, my friends and I applied our competitive streaks — we were teammates on Brown University’s swimming and diving team — to beach tanning. Who could get the darkest over a week in the Caribbean? Being pale, I never could. But that didn’t stop me from trying, or from picking up blistering sunburns as souvenirs. What an idiot — especially considering my father is a dermatologist. Now, after many years as a beauty editor and writer, I’m in medical school, studying to be (you guessed it) a dermatologist. Needless to say, I wear sunscreen religiously.

Which is why a particular piece of research came as a shock: A small but impossible-to-ignore study, published in Free Radical Biology & Medicine, has suggested that while sunscreen prevents free-radical damage to the skin from the sun, it also might cause damage.

According to this 2006 study from the University of California, Riverside, certain sunscreen ingredients may cause more free radicals to form than no sunscreen at all. If the findings are confirmed, the implications will be enormous — and sobering, given that women have been told for decades that regular sunscreen use is one of the best ways to minimize aging and the risk of skin cancer. The whispers started back in 2006, but they’re beginning to grow louder now; it took two years for news of the study to reach the public consciousness, because some doctors have been shying away from discussing the findings, loath to cause panic when the study was neither double blind, randomized, nor conducted on humans — nor has it been repeated. (In other words, don’t toss your sunscreen.)

Here’s the backstory: When we bake in the sun, the skin absorbs ultraviolet radiation (UVA and UVB rays) that can cause instability in the molecules of the body tissue, releasing harmful compounds called free radicals. Free radicals are molecules with an unpaired electron that, in an attempt to locate its electron “mate,” can disrupt the cells’ functions (seriously disrupt — if these electrons were at a bar, there would be smashed glasses, overturned bar stools, you name it).

When sunscreen is slathered on the skin, molecules in the sunscreen — the UV filters — cut down on the amount of radiation that can penetrate the skin. But according to this UC Riverside study, helmed by lead author Kerry Hanson, three commonly used, FDA approved sunscreen filters — octyl methoxycinnamate, octocrylene, and benzophenone-3, which is also known as oxybenzone — can boost the number of free radicals over time when they break down and are absorbed into the skin.

According to my analysis of the study findings, one hour after a ten-minute session of UV exposure, the ingredient benzophenone-3 elevated free radicals by 64 percent compared to the control, while octyl methoxycinnamate and octocrylene boosted free radicals by 33 percent and 16 percent, respectively. The rate of free-radical elevation caused by the sun itself has not been studied, according to several dermatologists.

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And it may not be just these three ingredients that cause problems, notes Hanson. The UC Riverside scientists chose to test these chemicals because they are “three of the most commonly used ingredients in sunscreens worldwide, and their chemical structures are very similar to other molecules that we know generate free radicals,” Hanson says. It seems that any sunscreen has the potential to create free radicals — including even the newer, more photostable versions and the purely physical blocks zinc and titanium dioxide, according to Hanson — but further study is needed. “We don’t have enough data yet to judge which sunscreens do not generate free radicals,” Hanson says.

Ironically enough, failure to reapply frequently seems to compound the damage to skin. “Using sunscreen once in the morning could potentially be worse than not using any at all if you spend a lot of time in the sun,” Hanson says. “Not reapplying every two hours would mean that you would have minimal sun protection, and the sunscreen itself could generate free radicals.” Trouble is, few of us reapply as often as we should (every two hours and after swimming, excessive sweating, and toweling off).

Great. For a medical student like me, this is like discovering the Easter Bunny doesn’t exist — or that it has fangs and claws. But how scared should I be?

Some dermatologists pooh-pooh the free-radical study at UC Riverside as small and inconclusive, noting that it didn’t use actual sunscreen — just individual ingredients. And some point out that the study used epidermal model tissue — genetically engineered skin — rather than a real human sample. “This study uses a skin model, and this sort of thing happens all the time: You get quirky findings that we can’t replicate because those things don’t happen in people,” says James M. Spencer, a clinical professor of dermatology at Mount Sinai School of Medicine in New York.

Hanson’s response to these criticisms? She says the study wasn’t done on people because the free-radical detecting technology is not approved for use on humans — and notes that the fake skin was “irradiated for only about the equivalent of ten minutes of unprotected time in the noonday summer sun” — quite a conservative test, considering the hours that some of us bake out there. Hanson adds that the study builds upon ten-year-old test-tube research that also suggested that some sunscreen ingredients contribute to free radicals.

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