'Water-Resistant' vs 'Waterproof': A Guide to Understanding Sunscreen Labels

The risk of developing the deadliest form of skin cancer, melanoma, may be more closely related to sun exposure in early life than in adulthood, researchers say. (Image credit: Ron Sumners | Dreamstime)

Sunscreens labeled as water-resistant have replaced those labeled as waterproof, in one of several changes in sun care product labeling that the U.S. Food and Drug Administration (FDA) recently introduced.

Year-round protection from the sun is the best way to lower the risk of skin cancer, experts say. Skin cancer is the most common type of cancer, and more than 3.5 million Americans will be diagnosed with the disease this year.

Under the rules that went into effect last summer, sunscreens that were labeled as water- or sweatproof are now labeled as either 40- or 80-minute "water-resistant" products. The reason behind this change is that these products only protect from the sun for a limited period of time once a person is exposed to water, Adam Friedman, director of dermatologic research at Montefiore Medical Center, said in a statement.

"Choose an 80-minute water-resistant sunscreen, and reapply after getting out of the pool, ocean or even toweling off from a good workout," Friedman advised. [Infographic: What to Look for on New Sunscreen Labels]

There has also been a change in the labeling of sunscreens with a low Sun Protection Factor (SPF) number. Products with SPF 2 to SPF 14 now must carry a warning label, stating that they can help prevent sunburn, but fail to protect skin against skin cancer or premature aging.

The FDA now also regulates sunscreens for their ability to protect against both UVA and UVB radiation, whereas before the agency only regulated products for their rating of protection against UVB radiation. Under the new rules, the phrase "broad spectrum" can appear only on products that proven to protect against both UVA and UVB rays.

Although it is UVB light that causes sunburn, UVA light may be "the silent killer," as Friedman called it, because "it does not cause sunburns, so it is hard to tell if you are getting harmful exposure," he said.

Research has shown that the skin's aging process progresses more slowly in people who apply UVA and UVB sunscreen every day, all year-round, he said.

“The most important things to remember are to generously apply a shot-glass worth of broad spectrum [including both UVA and UVB filters] SPF 30-50 sunscreen at least 15-20 minutes before sun exposure, and every two hours thereafter,” Friedman said. People should also wear hats, sunglasses and protective clothing, and avoid being in the sun between 10 a.m. and 4 p.m. in the summer.

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Staff Writer