Boost your sunscreen IQ

Hot-button sunscreen news has been making headlines recently. In this guide, the GH Beauty Lab and top skin doctors answer your top sunscreen questions, helping you keep your skin protected (and youthful!) all summer long. Do I really need SPF in the shade?

You should never skip sunscreen: A new study found that 78 percent of people who used only an umbrella on a sunny beach day experienced sunburn, versus 25 percent of those who used only SPF — likely because shade doesn’t block UV light from all angles. Your best bet is tripling up, says GH Beauty Lab Director Birnur Aral. “Apply sunscreen, stay in the shade and wear sunprotective clothing and sunglasses.” Do sunscreens cause cancer?

Despite negative rumors about certain sunscreen ingredients (like oxybenzone), “there’s no data to suggest that any ingredients in U.S. sunscreens are in amounts that could potentially cause cancer,” said Elizabeth K. Hale, a New York City dermatologist and a senior vice president of the Skin Cancer Foundation. “They are proven safe and effective for preventing skin cancer and premature skin aging with regular use.” Are high SPFs actually necessary?

Some sources have stated that as SPF numbers increase, the boost in protection is minimal. But that doesn’t mean you should rely on SPF 15 only. “Our tests have shown that people apply about onethird the amount of sunscreen necessary to achieve the SPF listed on the label,” Aral said. “So we recommend using at least broad-spectrum SPF 50 to compensate.” More reason to go high: “SPF 30 filters 96.7 percent of UV rays, meaning it allows 3.3 percent to reach skin, while SPF 60 filters 98.3 percent, allowing 1.7 percent through,” explained Steven Q. Wang, dermatologist and cofounder of Dr. Wang Herbal Skincare. “So SPF 30 actually lets twice as much UV reach skin as SPF 60.” But high SPF numbers can give you a false sense of security, so remember to reapply at least every two hours. Can SPF stand up to water and sweat?

Only for a certain amount of time. While the FDA used to allow sunscreens to be labeled water- and sweat-proof, regulations now mandate that they can be labeled as “waterand sweat-resistant” (up to 40 or 80 minutes), because no sunscreen can be com- pletely impervious to water and sweat ( just as no sunscreen can totally “block” the sun’s rays). According to Dr. Wang, the labeling means the formula maintained its SPF level on testers’ skin in a water bath for the indicated time. Beyond that, it should be reapplied. Is it true that not all sunscreens stop burns?

You may have seen reports that people burned when using certain sunscreens. But our experts agree: Sunscreens work if used correctly — and you have to reapply them at least every two hours. “Sunscreens are very effective at preventing sunburn,” Dr. Hale said. “Burns are more likely a reflection of people not using enough sunscreen with a high enough SPF and not reapplying regularly.” For the best protection, apply sunscreen liberally on all exposed areas before going outdoors (a shot glass-full for the body, a nickel-size dollop for the face; spread sprays evenly by hand), Aral said. Layer on a second coat “to help cover spots you missed the first time,” Dr. Wang suggests.