Dermatologist Warns UVA Rays Can Damage Skin Indoors, Urges Use of Broad-Spectrum Sunscreen

Skin cancer remains widespread in the United States, yet misconceptions about sun protection continue to put people at risk. One of the most overlooked dangers, experts say, is that ultraviolet (UV) exposure can occur even indoors — including while sitting near a window. Dr. Adam Friedman, professor and chair of dermatology at the George Washington University School of Medicine and Health Sciences, explained that many people misunderstand what sun protection factor (SPF) actually measures.

“SPF only refers to UVB, the type [of sun rays] that burn,” Friedman said, noting that it does not account for ultraviolet A (UVA) radiation. Unlike UVB, UVA rays penetrate deeper into the skin, damaging collagen and elastin, accelerating aging, and contributing to skin cancer.

Woman applying sunscreen | Source: Pexels

“The tricky thing about UVA rays is that they can affect your skin health even when you’re indoors,” Friedman said. “When you stand next to a window, UVB might be filtered out, but UVA isn’t. So you can get exposure and not even realize it.” He added: “UVA gets through clouds, so it’s kind of the silent killer. You’re getting exposed and being harmed, and don’t even feel or know about it.”

To reduce risk, Friedman recommends sunscreen with SPF 30 or higher, in line with the American Academy of Dermatology’s guidance, and stresses the importance of choosing broad-spectrum formulas that protect against both UVA and UVB rays.

While Friedman personally applies sunscreen once daily when not near windows, he advises more frequent application for those spending extended periods outdoors or indoors near natural light. “Technically, you should be reapplying every two hours. I say technically, because I’m a realist and who’s going to actually do that,” he said. “Do the best you can.”