Dr. Hirsch says there’s still a common misconception that there’s very little difference between SPF 30 and SPF 50, but “there is a meaningful difference.” Specifically, when you wear SPF 30, 1.5 times more UV is getting through the filter. Therefore, she recommends a minimum of SPF 50 for both face and body when you’re outside.
In addition to seeking out a high SPF number, make sure your sunscreen is labeled “broad-spectrum.” That means it protects against both UVB and UVA rays.
When should you use sunscreen?
It may sound silly, but unless it’s nighttime and you’re in bed, sleeping, you should probably wear sunscreen.
“No matter the time of year, the sun is always emitting harmful UV rays,” says board-certified dermatologist Mary Lupo, MD. “Even though you may not receive a sunburn in colder months, it’s important to keep the skin protected year round as these rays can cause premature aging and DNA damage.”
DNA damage, which can lead to skin cancer, is specifically caused by UVB rays. “They are highest in intensity between 10 A.M. and 4 P.M.,” says board-certified dermatologist Carolyn Stull, MD. UVA rays, on the other hand, “are present throughout the day and penetrate more deeply in the skin, causing damage to collagen and elastin and leading to photodamage.”
If you’re inside most of the day and anywhere near a window, that window may block UVB rays, but it won’t block UVA rays. Board-certified dermatologist Azadeh Shirazi, MD, says to make indoor application a habit. “After all, we all go outside to check the mail, walk the dog, and sit next to a window. Over time, this accumulation of UV radiation takes a toll on the health and appearance of our skin.”
And remember, you’re not just protecting yourself against skin damage caused by UVA rays when you’re indoors. “While the majority of blue light exposure is from the sun, our digital devices emit high energy visible light, and some sunscreens may offer protection against this,” Dr. Garshick says.
How often should you reapply your sunscreen?
In a word: very. “Reapply every two hours at a minimum but more often if sweating or immersed in water,” board-certified dermatologist Roberta Del Campo, MD, tells Allure, echoing the recommended reapplication frequency of every expert we spoke to. This is true for sunscreen that claims to be water-resistant, too.