Summer wouldn't be summer without the ritual of gooping on even more sunscreen than usual. But if you're relying on the lotion (or spray, or stick) to safeguard your skin from the cancer-causing effects of UV rays, then we need to fill you in on some crucial info. A new study from the journalNature found that sunscreen alone, even a high-number SPF, isn't a guarantee that you won't at some point develop melanoma, the rarest yet deadliest form of skin cancer.
Researchers applied sunscreen with an SPF of 50 to mice who were bred to be predisposed to melanoma. Compared to a group of mice sans sunscreen, the first group took 30 percent longer to develop melanoma. The takeaway: Though high-factor sunscreen helped reduce the damage UV rays do to skin cells on a molecular level, which in turn can lead to cancer, it wasn't enough to offer complete protection, researchers concluded.
That comes as no surprise to dermatologists, who have long reminded patients that protecting your skin also means having other weapons in your cancer-fighting arsenal, says New York City dermatologist Albert Lefkovits, M.D., associate clinical professor of dermatology at the Mount Sinai School of Medicine. That includes covering up with clothes or a broad-brimmed hat, staying under an umbrella or awning, and totally avoiding being outside during peak UV hours between 10 a.m. and 2 p.m. Sure you've heard these strategies before, but combined with regular use of a broad-spectrum sunscreen (meaning it repels UVA and UVB rays) of at least 30 SPF, they really will keep your skin healthy.
The other thing to know about melanoma is that unlike basal cell and squamous cell carcinoma—two more common, less lethal forms of skin cancer that are almost always caused by unprotected sun exposure—melanoma can appear on places on the body where, well, the sun doesn't shine, such as your butt, pubic area, and the bottoms of your feet, says Lefkovits. This suggests that melanoma is caused by other factors, like genetics, and bathing yourself in sunscreen may not even make a difference. In fact, the Environmental Protection Agency notes that there is no evidence that sunscreen protects against malignant melanoma like it protects against other types of skin cancer (like basal cell and squamous cell carcinoma). So even though this study was done on mice who were already more susceptible to melanoma, the results show that sunscreen alone may not prevent skin cancer, especially if you have a genetic predisposition for the disease.
Of course, this doesn't mean you should toss your SPF. Broad-spectrum sunscreens are still highly recommended as they protect against cancer-causing UVA and UVB rays. According to the researchers, a combination of sunscreen and careful covering up will reduce your risk of skin cancer. To fully protect against melanoma, it's important to go for yearly skin checks and have any weird spot or mark checked out ASAP so you can catch a growth before it becomes malignant, says Lefkovits.