Memorial Day rings in the summer season and, along with barbecue equipment, beach toys and sandals, stores are beginning to pad their shelves with sunscreen. That's a great thing: sun damage is responsible for 90 percent of nonmelanoma skin cancers in the United States, itself the most common form of cancer in the country, according to the Skin Cancer Foundation. In fact, more than 3.5 million cases of skin cancer are diagnosed in the U.S. each year.

“The risk of skin cancer is very real," FDA Commissioner Dr. Margaret Hamburg said in a recent statement in support of the government's first annual "Don’t Fry Day" on May 25. “The FDA strongly recommends that consumers regularly use a Broad Spectrum sunscreen with an SPF value of 15 or higher in combination with other protective measures to more effectively protect themselves and their families whenever they are in the sun.”

But with so many options on store shelves -- not to mention an impending change in the way that sunscreens are labeled and rated -- selecting the appropriate sun protection can be a confusing endeavor. On the one hand, the block is essential to prevent the skin’s absorption of damaging sun radiation that can cause free-radical damage and lead to skin cancer and premature aging. But new research has suggested that some chemicals found in leading sunscreen brands can actually increase the risk of some melanoma skin cancers. So what should you do?

We asked top dermatologists for their tips on what to look for as you stock up on your summer sunscreen supply:

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  • What Is Sunscreen Made Of?

    Sunscreens follow one of two formulas. So-called "chemical free" sunscreens are made with a heavy metal -- usually oxidized zinc, though sometimes titanium oxide. Zinc and titanium sit on the surface of the skin, serving as a reflective, protective cover against damaging sun rays. Think of them almost like a giant reflector, says Dr. Darrell Rigel, Clinical Professor of Dermatology at New York University Medical Center. "They're just like a mirror, reflecting ultraviolet light off," he says. <br><br> The other type of sunscreen is typically made with the chemical Oxybenzone, and is referred to as "organic" or "chemical" sunscreen.

  • Are Chemical Sunscreens Dangerous?

    Some people prefer chemical-free sunscreens to the more common lotions and sprays, made with Oxybenzone. That's because old research in rodents has shown a relationship between oxybenzone and melanoma, though the link is inconclusive and most accredited medical organizations <a href="http://www.skincancer.org/prevention/sun-protection/sunscreen/if-recent-attacks-on-sunscreen-concern-you" target="_hplink">do not consider it viable</a>. Additionally, oxybenzone is an endocrine disruptor that mimics estrogen -- a concern for many people who try to avoid synthetic hormones. <br><br> "Oxybenzone is one of the oldest and most used sunscreen ingredients in the world, having been in use since the 1970s, and to date there have been no human cases of hormonal disruption documented," says Dr. Jessica J. Krant, MD, MPH, founder of the Art of Dermatology in New York City, and an assistant clinical professor of dermatology at SUNY Downstate Medical Center.

  • Is One Type Better Than The Other?

    While the cancer link to oxybenzone isn't clear, there are other reasons a person might not want to use a chemical-based sunscreen: first of all, they have a shorter half-life, according to Rigel. Their protection begins to degrade after two hours, compared to zinc-based lotions' eight hours. <br><br> But Zinc and titanium lotions are by no means perfect: because they sit on the surface of the skin, they are less resistant to water. Swimmers and other active people will have to reapply frequently. Additionally, as they degrade, the metals form clumps on the skin's surface -- this leads to patches of protected skin and patches without any protection at all. By contrast, oxybenzone-based creams degrade evenly. <br><br> One additional problem with zinc and titanium based creams? They don't look great. Especially for the dark complected among us, the metal formulas can leave a noticeable white coating. If aesthetics are a concern, a beachgoer may forgo the lotion altogether -- and that's the only form of unacceptible sunscreen: none. <br><br> "Honestly, the best sunscreen is whatever the patient uses," says Dr. Bobby Buka, a dermatologist in private practice in New York City. "I'm not going to fight the battle about formulation."

  • What SPF Do I Need?

    While some sun lotions may offer SPFs as low as two, the general consensus is that, to be effective, a lotion must have an SPF of at least 15, though the American Academy of Dermatology recommends a sunscreen with an SPF of 30 or more. "Remember this only applies to UVB coverage and requires sufficient amounts," cautions Krant.

  • Is UVA Protection As Important As UVB?

    SPF applies only to UVB rays, but we now know that UVA rays can be just as damaging -- and may be even more closely associated with premature skin aging. The new FDA label regulations require manufacturers to rate their UVA protection on a scale of five stars, but until those rules go into effect next year, make sure you look for a broad-spectrum sunscreen that protects against both types of ultraviolet rays. <br><br> Though beware: broad-spectrum doesn't necessarily mean you're in the clear. As Rigel explains, companies need only provide a tiny amount of UVA protection to give their product that label. "What's really important is proportionality," he explains, and that's factored into the future labels, but not the current ones. Using the current labels, "you'd basically have to be organic chemists to figure it out," Rigler says. <br><br> Any label that discusses proportionality or the test used to arrive at UVA protection scoring, the critical wavelength test, may be the best bet.

  • Should I Use Waterproof Block?

    There's no such thing as waterproof sunscreen. In fact, the new FDA guidelines will require that sunblocks reduce their claims to "water resistant," "water resistant 40" and "water resistant 80." The numbers connote how many minutes they are able to uphold protection after getting wet. Older bottles may still say "waterproof," but don't believe the hype. <br><br> If you're spending a great deal of time splashing around -- or you happen to sweat more than the average person, up your frequency of applications.

  • How Much And How Frequently Should I Apply?

    Most recommendations suggest reapplying every two hours, because that's the point of degradation for oxybenzone-based sunscreens, which are the most common. But a zinc sunscreen can be applied every four, six or even eight hours, according to Dr. Bobby Buka. <br><br> However, as Buka explains, all testing of sunscreens is done at a higher concentration that we don't replicate on the beach, at two milligrams per square centimeter. Given that discrepancy, it's better to reapply more frequently -- and that's especially true for those who are sweating, swimming or otherwise exposing their skin to water. <br><br> The American Academy of Dermatology <a href="http://www.aad.org/media-resources/stats-and-facts/prevention-and-care/sunscreens" target="_hplink">recommends</a> using about one ounce (enough to fill a shot glass) to cover all exposed parts of the body, though that should be adjusted based on size.

  • Do I Really Need To Wait 20 Minutes After Applying For My Sunscreen To Work?

    Sometimes. Oxybenzone-based sunscreens need that long to penetrate the dermis and become active. But if you're wearing a barrier sunscreen like zinc, you're ready to go as soon as you apply.

  • Are Sprays As Good As Lotions?

    Yes. Sprays, lotions, oils -- whatever you truly use, as long as you are thorough, is a good product, agreed the experts. People who use sprays are slightly more likely to miss some spots, so Rigel recommends spraying two coats.