Myth: “Anything above SPF 15 is a waste.”
The FDA is still debating the merits of super-high SPFs, but many derms agree that there are meaningful differences between 15, 30, and 50, especially because we’re just so bad at applying sunscreen properly. “If you use SPF 50, you really get the protection of an SPF 20 based on how people actually apply it,” says New York City dermatologist Doris Day, MD. That includes both applying too little in the first place and not reapplying often enough (every two hours or so when you’re at the beach or pool all day).
The doctors we talked to generally recommended a minimum of SPF 30 for everyday sunscreen and SPF 50 for long stints outside.
Myth: “But I need sun to get enough vitamin D.”
This is a common misconception. First, most people don’t apply sunscreen well enough to prevent skin from producing vitamin D. Second, you need much less time in the sun to make adequate levels than you might think. If your skin just kept making vitamin D in response to sunlight, it would reach toxic levels, explains Day. After 15 minutes or so, the system overloads and production stops. Being tan isn’t a good indicator of healthy vitamin D levels, says Ronnie Klein, MD, assistant professor, Yale Dermatology.
One classic study of Hawaiian surfers found that although all participants were tanned, many were still vitamin D deficient. “You can get enough vitamin D from a mix of diet, supplements, and incidental sun exposure,” says Klein.
Myth: “I don’t need sunscreen if it’s not ‘peak tanning hours.’”
Your likelihood of burning is worse when the sun is directly overhead—from about 10 a.m. to 2 p.m.—but dermatologists were unanimous that tanning at any hour of the day isn’t safe. Although UVB rays, which cause burning and some skin cancers, peak at mid-day, UVA rays, which contribute to aging and some skin cancers—are constant all day long, Klein says. And Day says that she often sees the worst sunburns on cloudy days. “Clouds block infrared rays, so you don’t feel hot, but they only block 20 per cent of UV rays so you can still get burned,” she says, noting that people often spend more time outdoors and skip sunscreen on cloudier days, which makes matters worse.