If you're at the beach or pool, applying sunscreen before and after you've been in the water is a must, a cancer specialist says.
The intensity of exposure to harmful ultraviolet (UV) rays "is higher under water than it is above water," said Dr. Arun Mavanur. He is a surgical oncologist at the Alvin & Lois Lapidus Cancer Institute at LifeBridge Health, in Baltimore.
"UV rays also are reflected off the surface of the water, so overall you tend to get more exposure while you're in the water," he added. That's why it's essential to apply sunscreen to exposed skin 15 to 30 minutes before heading outdoors. Reapply every two hours while outdoors and after swimming, Mavanur advised.
He noted that some people mistakenly believe they need to apply sunscreen just once a day if it has a high sun protection factor (SPF) rating. But the SPF rating isn't an indicator of how long you can stay in the sun or how often you should apply your sunscreen. It's simply a rating of the sunscreen's effectiveness in protecting the skin from UV light, Mavanur noted.
And while some sunscreens are labeled water-resistant, Mavanur pointed out that "there really is no such thing as a waterproof sunscreen, so once you get out of water, it's important to reapply it."
Water-resistant sunscreen lasts only 40 to 80 minutes on wet skin, which is why you need to reapply it after spending time in the water or sweating heavily.
"If you're out in the sun and working in the garden and sweating, you still have to apply sunscreen every couple of hours," Mavanur said.
He recommends using a broad-spectrum, water-resistant sunscreen with an SPF of 30 or higher. Broad-spectrum means it protects against the two main types of UV light that contribute to skin cancer risk: ultraviolet A (UVA) and ultraviolet B (UVB).
UVA is associated with skin aging. UVB is associated with sunburn and is believed to cause most skin cancers. An SPF-30 sunscreen blocks 97% of the sun's UVB rays.
The American Cancer Society has more on sun safety.
SOURCE: LifeBridge Health, news release, Aug. 13, 2021