Sunscreen has just gotten a whole lot simpler. And safer. Why? New FDA rules are helping ensure that we get the protection we pay for, and with skin cancer on the rise (one in five Americans will develop skin cancer in the course of a lifetime), these changes couldn't come at a better time.

Key fixes: Sunscreens will now be labeled "water resistant" (as opposed to waterproof or sweatproof); they can no longer be called "sunblocks" (as it overstates their effectiveness); and they can no longer claim to provide instant sun protection or to last more than two hours without reapplication. On top of that, sunscreens can be labeled "broad spectrum" only if they protect equally against UVB (the main culprit of skin cancer) and UVA rays, which cause aging.

"Up until now, SPF measured only UVB protection, so a sunscreen could say it was broad spectrum even if it blocked a tiny bit of UVA," said Dr. Katie Rodan, a San Francisco dermatologist. Yet even with these changes, most of us still have questions. Here are the ones you sent to us, answered by our dermatologists.

How much sunscreen do I really need to put on?

Anytime you're planning to be outdoors, go with an SPF of at least 30 (45 for a little extra insurance) and put plenty on. The rule of thumb is one ounce (the size of a shot glass) on your body, and a teaspoon for your face, but derms advise being even more generous. Reapply every two hours—more often if you're in and out of the water.

Are there any sunscreens good for oily skin?

Yes. What you want is an oil-free mineral block in an ultralight gel or liquid. "Mineral sunscreens help mask redness, and because they reflect UV light, they help keep your skin surface cooler," Dr. Rodan noted. While you're at it, keep your skin clean by always washing your face after working up a sweat outdoors: Summer breakouts often have more to do with sweating than wearing sunscreen.

How do I know if I'm spraying on enough sunscreen? I feel like it all blows away!

Spray sunscreens aren't as powerful as lotions, so the trick is to look for one labeled "continuous spray" (no need to pump; it keeps spraying as long as your finger stays on the button) and apply two coats—not one—every hour, Rodan said.
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What should I look for in a sunscreen if I have sensitive skin?

All the dermatologists we interviewed recommend mineral-based or physical sunscreens made with micronized titanium dioxide and/or zinc oxide instead of chemical sunscreens because they're less likely to irritate sensitive skin. Plus, the latest mineral sunscreens give the gentle protection of a physical sunscreen without leaving a white cast.

Is sunscreen really necessary for lips?

Absolutely. In the past, it wasn't unusual for lip products to come with little or no SPF. Thankfully, many companies have upped the level of protection in lip balms. That's critical because skin cancers on the lower lip, in particular, are especially aggressive. "These cancers are dangerous, as they're more likely to spread," explained Dr. Jeremy Green, a Miami dermatologist. Look for a balm with an SPF of at least 30.

What's the easiest way to stay protected when I'm working out?

Dab an SPF (of at least 30) stick or gel on your face, neck, and chest, and on hot spots like shoulders and the backs of your hands. "The non-tacky sticks are great because they really stay put," said Washington, D.C.–based dermatologist Dr. Tina Alster. For the rest of your body, use a sunscreen spray. If you're swimming or perspiring a lot, opt for one of the new formulas that are marked "water resistant" for up to 40 or 80 minutes.

I hate reapplying! Can I throw on a long-sleeved T-shirt instead at the beach?

"Most cotton shirts are no substitute for sunscreen," Rodan said. "At best, they give you a UPF (ultraviolet protection factor, the equivalent of SPF for clothing) of 8—and if they get wet, that devolves to UPF 2." Instead, invest in a long-sleeved rash guard—a type of shirt made up of a spandex and nylon mix that was originally used for water sports, but is now popular as a sun protector. Look for one with a UPF rating of 50+. "Those things are lifesavers—total protection, even when wet," Alster said. Likewise, your sun hat should be floppy, wide-brimmed, and made from a tightly woven material.

Will my SPF foundation do the trick for workdays?

"You'd have to slap on a heck of a lot to make it truly effective," Green said. A better idea: Layer. Wash your face, swipe on a few drops of antioxidant serum to boost your protection, and apply a tinted moisturizer or foundation with SPF 15 or more. Top it with an ultrafine SPF mineral powder. Green recommends carrying the powder in your bag for touch-ups during the day—especially if you're lunching alfresco.