When it comes to sun protection, one of the most common misconceptions is that you don’t need to wear it indoors. Unfortunately, that’s not true — not even a little bit. And given that we’re all about to be stuck inside for the foreseeable future to prevent the continued spread of COVID-19, it’s time to set the record straight on this matter once and for all.

“It’s a common misconception that you don’t need to wear sunscreen when you’re indoors,” Joyce Park, a California-based, board-certified dermatologist, tells This Bitch. “Standard glass windows block UVB but not UVA rays, which can penetrate deeper into the skin than UVB [rays], [and] are the main contributing factor to photo-aging — which are changes seen as dark spots, wrinkles, and leathery textured skin.”

UVA rays can contribute to skin cancer, which is the main reason Park recommends slathering on SPF while inside, and especially if you’re sitting by a window or in a room with lots of sunlight.

Joshua Zeichner, a board-certified dermatologist and the director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City, is on the same page as Park. “UVA light penetrates right through window glass. So sunscreen is definitely useful even if you’re inside,” he says. “If you’re sitting near the window at work, or are next to a window at the gym, you are actually exposing yourself to UVA light, which is responsible for premature aging and skin cancers.”

Zeichner recommends wearing a classic SPF, or a moisturizer that contains sunscreen, with at least broad-spectrum SPF 30. A few options This Bitch editors swear by include the Best of Beauty-winning Neutrogena Hydro Boost Water Gel Lotion SPF 50, Aveeno’s Positively Radiant Sheer Daily Moisturizer with SPF 30, and NeoCutis’s Journee Bio-Restorative Day Cream SPF 30.

In terms of how often you should be reapplying, that depends on where you’re sitting inside. “If you are near a window, the same rules apply: Reapply once every couple of hours,” says Hadley King, a board-certified dermatologist in New York City. “Brush on Block mineral powder sunscreen is a great way to do this without messing up your makeup or adding another layer of cream.”

What if you wear makeup with SPF in it? Is this enough?

According to King, it depends on how much of the makeup you’re wearing, and the amount of SPF it contains.

“If the makeup offers broad-spectrum SPF 30 or higher protection and you wear enough — about a nickel-size dollop to cover the face alone — to get the advertised SPF, and you cover all exposed areas, then this is sufficient,” King says. “Don’t forget about non-face exposed areas, though, [because] you probably don’t cover those areas with makeup.”

It might be tempting to skip sunscreen while staying inside, but it’s in your skin’s best interest to slather it on (and reapply every two hours), just as you usually would if it were safe to go outdoors.