Yes, You Still Need To Wear SPF If You're Indoors All Day. Here's Why

It's no secret that wearing SPF is touted by experts as one of the best ways to protect your skin from premature aging and skin cancer, and we all (hopefully) know by now that slathering it on is a must before heading outside for a day in the sun. But do you still need to bother with it if you're inside? As it turns out, you receive far more sun exposure indoors than you might think, making it essential to work an SPF into your morning skincare routine (even if you aren't a lifeguard and your work involves taking Zoom meetings from your dining room table).

According to Nielsen, sunscreen sales declined by as much as 17% in the first two weeks of March 2020 during the initial onset of the COVID-19 pandemic as Americans began to plan for quarantine and prepare to not leave their homes for an extended period of time (via NPR). However, board-certified dermatologist Robyn Gmyrek told NBC News that it is "crucial" to wear SPF year-round, regardless if you even step foot outside, echoing a growing number of her colleagues in the industry — but why?

Windows don't filter UVA rays

It's a common thought that being indoors offers ample protection from the sun's harmful UV rays, but unless you are in a windowless room, that's not entirely true. According to Dr. Elizabeth Hale, a board-certified dermatologist and senior vice president of The Skin Cancer Foundation, "People classically think about UVB rays because they are what cause sunburns in the summertime," she told InStyle. "In reality, UVA rays are what cause sun damage regardless of the season of the weather because they have longer wavelengths that penetrate through clouds. By similar logic, UVA rays also penetrate through windows."

So, whether you work in a cubicle or take your Zoom meetings from the comfort of your own home, where there are windows, there, too, is sun exposure — even if it's a cloudy day and you spend the entirety of it inside responding to emails.

Without applying SPF to protect your complexion from the UVA rays that penetrate through your windows, your skin is more susceptible to sun damage and premature aging. "Because UVA rays penetrate deeper into the skin and cause DNA damage, they break down collagen and elastin," board-certified dermatologist Dr. Marie Hayag explained to InStyle. "This makes them responsible for accelerated photodamage including wrinkles, leathery skin, sunspots, and skin cancer."

Be extra diligent if you use these skincare products

Additionally, some prescription and over-the-counter skin care products can make your skin ultra-sensitive to sunlight and increase your risk of sun damage and burning, even if you never step foot outside. So, while experts recommend you take the proper precautions to protect yourself from the sun's rays that come in through your window(s), it's even more important if you are using a topical product with increased sun sensitivity listed as a side effect.

"Ingredients that exfoliate or encourage skin cell turnover are the biggest culprits of causing photosensitivity," says Deborah S. Sarnoff, MD, president of The Skin Cancer Foundation (via the Skin Cancer Foundation). "When you remove dead skin cells and expose the new, more delicate skin underneath, your skin becomes more susceptible to damage from UV rays." This includes retinols, AHA and BHAs such as glycolic and salicylic acid, and even certain antibacterial and anti-fungal topical medications.

Dr. Sarnoff also notes that in addition to retinol making your skin more sensitive to sunlight, the beneficial anti-aging effects of retinol can actually be made less effective by sunlight — making it "doubly important" for those who wear it to be proactive about applying SPF. "Regardless of if or when you use skin care products that cause photosensitivity, sun protection is important every day," she said. "You should be extra vigilant about applying sunscreen if you're also using a retinol, AHAs, BHAs or hydroquinone."

What kind of sunscreen should you wear?

When it comes to daily sun protection, experts generally recommend using SPF 30 or higher, as long as it is labeled as broad-spectrum (and yes, there is a difference in SPF numbers). Both chemical and mineral sunscreens are effective at protecting you against UV rays. Since UVA light does not lead to any sort of tan on your skin, it can be difficult for you to measure exactly how much sun exposure you are getting on a daily basis, which is why it's best to ensure you are protecting yourself with a blanket of at least SPF 30 every day.

According to the Skin Cancer Foundation, chemical sunscreens prevent UV rays from damaging your skin by absorbing them. In contrast, mineral sunscreens act as a physical barrier by sitting on the skin's surface and preventing the sun's harmful rays from penetrating it. 

While both are proven effective at combating some of the most damaging effects of UV radiation, Dr. Hale told InStyle that the zinc oxide and iron dioxide found in mineral sunscreens work to not only protect your skin from UV rays but from the harmful effects of blue light as well (which you are exposed to a lot of if you work from a computer). She also recommends looking for a formula that contains antioxidants, which can also aid in combating the effects of blue light exposure.