Exposure to UV rays can happen just by sitting near a window: You 'don't even feel or know it,' dermatologist says—how to stay protected

Skin cancer is prevalent in the United States, and still there are many misconceptions about skin protection — especially when it comes to sunscreen.

There are plenty of things people aren’t aware of when it comes to how sun exposure can affect the skin, says Dr. Adam Friedman, professor and chair of dermatology at GW School of Medicine and Health Sciences. From where on the body you should apply sunscreen to how often you should be reapplying throughout the day.

A fact that would surprise many people when it comes to sunscreen, Friedman says, is what SPF actually protects against.

“SPF only refers to UVB, the type [of sun rays] that burn,” he says. SPF doesn’t factor in ultraviolet A radiation which can penetrate into the skin deeper than UVB rays.

UVA rays are “actually more associated with accelerated skin aging. It damages collagen, elastin. [It’s] also associated with skin cancer, but it doesn’t burn like ultraviolet B does,” Friedman says.