Welcome to Ask a Derm, a series from SELF in which board-certified dermatologists answer your pressing questions about skin, hair, and nail health. For this installment, we tapped Susan Massick, MD, FAAD, an associate professor of dermatology at The Ohio State University College of Medicine focused on patient care, resident education, and community engagement. Her specialties include acne, moles, skin cancer, and eczema.
Regularly applying sunscreen may be important for your health, but frankly, it’s tedious as hell. You have to generously slather the stuff on every body part that sees the light of day, and then reapply it every couple of hours if you’re spending time outdoors. Not to mention that finding a formula you love that works for your skin tone and type can take a lot of trial and error. Given how not fun those SPF steps are, we don’t blame you for wondering if you still have to put yourself through them if you’re holed up indoors in the winter (or any time of year, for that matter).
It makes sense that you still need sun protection if you’re commuting to work or braving the cold for a morning run, say, but what if you’ll only be opening your front door to check your mail or accept your Seamless delivery? We asked Susan Massick, MD, board-certified dermatologist and associate professor of dermatology at The Ohio State University College of Medicine, for some guidance.
“Consistently protecting your skin from UV light exposure can help prevent skin cancer and photodamage, including signs of premature aging, like wrinkles, and hyperpigmentation,” Dr. Massick says. Unfortunately, yes, that means “it is always a good idea to wear sunscreen daily—whether it’s sunny or cloudy, summer or winter, warm or cold, or you’re planning on being outside or staying indoors,” she adds.
The why behind this golden rule requires a refresher that might bring you back to science class: Ultraviolet (UV) light includes UVA rays (the biggest instigator of premature skin aging and UVB rays (which cause sunburns and play the biggest role in the development skin cancer), as SELF previously reported.
“Window glass will generally block UVB rays but does not block all UVA rays, so even if you’re staying indoors, natural sunlight will be coming through your windows,” Dr. Massick explains. She adds that the percentage of UVA rays (which can also contribute to skin cancer, by the way) that reach your skin depends on a variety of factors, including the type, color, and thickness of the glass, as well as whether or not it’s coated. “High-energy visible light, such as the blue light that makes the sky appear blue on sunny days, can also penetrate windows and contribute to hyperpigmentation,” she says.
On that note: Blue light is also what helps make the screens on your laptop, phone, TV, and other precious devices clear and bright. We need more research on how repeated exposure to this particular form of blue light affects the skin, but Dr. Massick suggests playing it safe: Even if your space doesn’t get much sun or you’re not hanging out anywhere near a window, if you’re regularly staring at a screen throughout the day, your skin can still benefit from a layer of SPF, she says.