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Is it true that "waterproof" sunscreen doesn't need to be reapplied after swimming?

Answer by:
Karyn Grossman, MD

Dermatologist, WebMD Medical Expert
St. John's Hospital

FALSE. It's no surprise researchers at the Colorado School of Public Health recently found that vacations near the water were associated with a 5% increase in small skin moles, which in turn boosts a person's risk of melanoma. While the FDA recognizes the term "water resistant" (which means a sunscreen offers SPF protection after 40 minutes of exposure to water), it does not acknowledge the term "waterproof." 

"No sunscreen is truly waterproof," says Amy Wechsler, MD, dermatologist and author of The Mind-Beauty Connection: 9 Days to Reverse Stress Aging and Reveal More Youthful, Beautiful Skin. Sunscreen should be reapplied every two to three hours and every time you get out of the water if you're doing laps in the pool or splashing around in the ocean, she says.