by Liz Szabo, Reprinted from the August 4, 2010 edition of USA Today
With an ever-growing number of sun-protection products on the market, many consumers wonder which offer the best defense against wrinkles, burns and cancer. Here, experts explain the science behind some of these products - and whether they're really worth the money.
Q: What does the SPF number on sunscreens mean?
A: The sunburn protection factor, or SPF, measures protection against only ultraviolet radiation B, UVB, which causes burning, says Henry Lim, chairman of dermatology at Henry Ford Hospital in Detroit.
The SPF level doesn't measure protection against ultraviolet radiation A, UVA, which causes aging of the skin, says Otis Brawley, chief medical officer of the American Cancer Society. Both types of UV rays cause cancer, he says. Experts say consumers should look for sunscreens that protect against both UVA and UVB rays.
Q: How protective are sunscreens?
A: Sunscreens can give people a false sense of security, Brawley says. He says people shouldn't use sunscreen to stay in the sun extra long. While sunscreen is important, covering up with a hat and long sleeves offers more protection, he says.
"You can actually use sunscreen to avoid sunburn, so you can get more UV radiation and increase your risk of melanoma," Brawley says.
Q: Do sunscreens offer everyone the same protection?
A: No. Brawley notes that SPF ratings are averages. For someone who's prone to burning, a sunscreen that's labeled SPF 30 may act more like an SPF 10. For another person, the same product may act like an SPF 60, he says.
Q: Do the new SPF 100 sunscreens offer twice as much protection as SPF 50?
A: Not necessarily. The SPF testing system may not accurately measure anything above SPF 50, according to the Food and Drug Administration. In 2007, the FDA proposed limiting the maximum l abeled SPF value to 50. Sunscreens with additional protection could be labeled "SPF 50+," according to the proposed rule, which is still being developed.
The SkinCancer Foundation, which promotes sun protection, says that in most cases, "SPFs beyond 50 are unnecessary."
Q: So how much SPF do you really need?
A: The American Academy of Dermatology recommends both adults and children use a sunscreen with an SPF of at least 30. Babies under 6 months shouldn't get any direct sunlight, according to the American Academy of Pediatrics.
It may be even more important to use enough sunscreen, Lim says. He notes that most people get much less sunburn protection than they might think simply because they don't use enough of the product.
The average person needs about 1 ounce of sunscreen - enough to fill a shot glass - to cover the body. Most people use only one-quarter to one-half that amount, Lim says.
Q: Is there any advantage to wearing clothing labeled UPF 50?
A: Yes, Lim says. Sunscreens can rub off or wash away over time. But clothing labeled UPF 50, or ultraviolet protection factor 50, offers long-lasting protection against UVA and UVB rays.
Q: What about UPF 50 umbrellas?
A: You still need sunscreen or protective clothing under these umbrellas, Lim says. That's because the umbrella protects people only from direct sunlight, not the ultraviolet rays reflected up from the sand or pavement.
Q: What kind of ingredients should you look for?
A: In addition to buying sunscreen with "broad spectrum" protection against both UVA and UVB rays, the Skin Cancer Foundation recommends choosing a sunscreen with "some combination" of these ingredients, which block UVA rays:
avobenzone (also known as Parsol 1789), ecamsule
(also known as Mexoryl), titanium dioxide and zinc
Q: Are chemicals in sunscreens safe?
A: Although scientists disagree, most doctors say there's no clear evidence that sunscreen ingredients are harmful.
A report in May from the Environmental Working Group, an advocacy organization that studies chemicals in consumer products, raised concerns about two ingredients: retinyl palmitate, a form of vitamin A that has been linked to skin cancer in laboratory rats, and oxybenzone, an estrogen-like chemical that, in animal studies, can cause allergies and alter the body's hormone system.
The Skin Cancer Foundation says none of these chemicals has been shown to cause harm in people.
Though Lim says he's "keeping an open mind" about the environmental group's concerns, he notes that dermatologists have used retinyl palmitate to treat acne and wrinkles for many years. "There haven't been any concerns about cancer," Lim says. "It's always a significant jump to draw conclusions from animals about humans."