Skin cancer accounts for nearly half of all cancers in the United States. Each year more than 5.4 million cases of basal and squamous cell skin cancer are found and melanoma, the most serious type of skin cancer, is expected to account for more than 76,000 cases of skin cancer in 2016, according to the American Cancer Society.

Roughly 90 percent of non-melanoma skin cancers and 65 percent of melanoma skin cancers are associated with exposure to ultraviolet (UV) radiation from the sun.

Given those statistics, it doesn’t take a rocket scientist to recognize that minimizing sun exposure is a prudent step in lessening the risk of skin cancer, not to mention decreasing premature aging of the skin. Obviously this doesn’t mean we need to move into caves or begin to take cues from the vampire set. But aside from avoiding peak sun (10 a.m. to 2 p.m.) and employing protective clothing, it’s smart to get a grasp on the basics about the increasingly complicated world of sunscreen.

With that in mind, here’s the skinny on how the Food and Drug Administration’s (FDA) labeling works, what different types of sunscreen are available, and how to apply it — all which might just save your hide.

What the labels mean

Broad-Spectrum: Sunscreens that pass the FDA’s broad-spectrum test may be labeled as “Broad-Spectrum SPF [value]” on the label. Broad-spectrum products provide protection against both ultraviolet B radiation (UVB) and ultraviolet A radiation (UVA) – and offer the best protection. Sunburn is mostly caused by UVB, while both UVB and UVA can cause sunburn, skin cancer and premature skin aging.

Sun Protection Factor (SPF): The SPF value indicates the level of sunburn protection provided by a product. All sunscreens must be tested according to an SPF test, which measures the amount of UV radiation exposure it takes to cause sunburn when a person is using a sunscreen, in comparison to how much UV exposure it takes to cause a sunburn when they are not using a sunscreen. Higher SPF values mean better protection against sunburn.

The FDA has proposed a regulation that would require sunscreen products that have SPF values higher than 50 to be labeled merely as “SPF 50+.” They do not have adequate data proving that products with SPF values higher than 50 provide additional protection compared to products with SPF values of 50.

Consumer Reports recently tested more than 60 lotions, sprays and sticks claiming to have SPF 30 or higher, which is the minimum level recommended by the American Academy of Dermatology. They found 43 percent of them did not meet the SPF claim on the label. “The most problematic products were Banana Boat Kids Tear-Free, Sting-Free Lotion and CVS brand Kids Sun Lotion, which were both labeled as SPF 50 but were found to have only SPF 8,” CNN reports. From Consumer Reports:

Those results aren’t a fluke; we’ve observed this pattern in our testing over the past four years. Of all the sunscreens we’ve tested over that stretch of time, fully half came in below the SPF number printed on the label, and a third registered below an SPF 30.

Broad Spectrum SPF 2-14: Only broad-spectrum sunscreens with an SPF value of 15 or higher can claim to reduce the risk of skin cancer and early skin aging. Non-broad-spectrum sunscreens and broad-spectrum sunscreens with an SPF value between 2 and 14 can only claim to help prevent sunburn.

Waterproof, sweatproof, sunblock, instant protection: Manufacturers can no longer label sunscreens as “waterproof” or “sweatproof,” or call their products “sunblocks,” because these claims are misleading. Sunscreens also cannot claim to provide sun protection for more than two hours without reapplication, or claim to provide protection immediately after application (“instant protection”) without submitting data to support these claims and obtaining FDA approval.

Water Resistant: Water resistance claims on the front label must indicate whether the sunscreen remains effective for 40 minutes or 80 minutes while swimming or perspiring, based on standard testing. Sunscreens that are not water resistant must include directions instructing consumers to use a water-resistant sunscreen if swimming or sweating. A recent study by researchers at Northwestern and Duke universities found that nearly 40 percent of popular sunscreens don’t meet the American Academy of Dermatology’s sunscreen criteria, due to their lack of water resistance. Industry groups released a statement however, arguing that sunscreens do not have to be water resistant to be effective.

Basic types of sunscreen

The two basic components of sunscreen that make it work are either chemical ingredients or physical ingredients (many sunscreens use a combination of both).

Chemical ingredients: As the Environmental Protection Agency describes it, broad-spectrum sunscreens often contain a number of chemical ingredients that absorb UVA and UVB radiation. Many sunscreens contain UVA-absorbing avobenzone or a benzophenone (like dioxybenzone, oxybenzone, or sulisobenzone) in addition to UVB-absorbing chemical ingredients. In rare cases, chemical ingredients cause skin reactions, including acne, burning, blisters, dryness, itching, rash, redness, stinging, swelling and tightening of the skin. These reactions are most commonly associated with para-aminobenzoic acid (PABA)-based sunscreens and those containing benzophenones. Some sunscreens also contain alcohol, fragrances or preservatives, and should be avoided by people with sensitive skin.

Physical ingredients: The physical compounds titanium dioxide and zinc oxide reflect, scatter, and absorb both UVA and UVB rays. These ingredients generally do not cause allergic reactions. Unlike the white greasepaint look of older physical sunscreens, new technology allows the particle sizes of zinc oxide and titanium dioxide to be reduced, making the new formulas more transparent.

Which is best?: Healthy living watchdog Environmental Working Group has paid diligent attention to sunscreens as part of its comprehensive Skin Deep database. The group’s top-rated sunscreens (the ones they consider healthiest) all contain physical ingredients. They recommend these as, “the right choice for people who are looking for the best UVA protection without any sunscreen chemical considered to be a potential hormone disrupter. None of the products contain oxybenzone or vitamin A and none are sprayed or powdered.”

If you choose spray sunscreen, especially on children, make sure to first spray on your hands and then apply it. (Photo: sakkmesterke/Shutterstock)

A note on spray sunscreens: The FDA has requested additional data to establish effectiveness and to determine whether spray sunscreens present a safety concern. According to Consumer Reports, the particular concern is the possibility that people might accidentally inhale the ingredients, a risk that’s greatest in children. The group recommends not using sprays on children, unless no other product is available. Another area of concern is just how effective are spray sunscreens. Many dermatologists agree that lotion-based sunscreen is a better choice than a spray. Dr. John Zampella told Business Insider that spray sunscreens provide less even coverage and most of it ends up in the air rather than on one’s body.

How to apply sunscreen lotion

While you may think you’re slathering enough sunscreen on your skin, more than likely you’re probably not. A 2018 study from King’s College in London shows that most people apply sunscreen too thinly and miss entire sections on their body. To receive the optimal level of protection, scientists suggest using 2 mg per square centimeter of skin. (One dermatologist breaks down the math and shows exactly how much that is.) They also recommend using a higher SPF to account for the likelihood of not using enough sunscreen.

“This research demonstrates why it’s so important to choose an SPF of 30 or more. In theory, an SPF of 15 should be sufficient, but we know that in real-world situations, we need the additional protection offered by a higher SPF,” said Nina Goad of the British Association of Dermatologists. “It also shows why we shouldn’t rely on sunscreen alone for sun protection, but we should also use clothing and shade. An extra consideration is that when we apply sunscreen, we are prone to missing patches of skin, as well as applying it too thinly.”

Here are some recommendations:

• Apply sunscreen around 30 minutes before being in the sun for best absorption by the skin; it will be less likely to wash off when you perspire.
• Shake well before use to mix particles that might not be mixed well in the container.
• Make sure to apply an ample amount. (See above)
• Use on all parts of your skin exposed to the sun, including the ears, back, shoulders, and the back of the knees and legs. Don’t forget beneath straps or your eyelids, one of the most-missed areas, according to research published in 2019 in PLOS One.
• Reapply sunscreen at least every two hours — and more if you’re sweating or getting in and out of the water.
• Try a sunscreen with different chemicals if your skin reacts badly to one that you are using.
• Use a water-based sunscreen if you have oily skin or are prone to acne.
• Some sunscreen ingredients can degrade over time, so check the expiration date.

If you really want to know how well you’re applying sunscreen, go find a UV light and prepare to be amazed. And if you don’t have one handy, just watch Thomas Leveritt’s film (above), in which the filmmaker and artist showed people what they looked like in UV light — and invited them to put on some sunscreen already!

Editor’s note: This story has been updated since it was originally published in May 2012.

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A user’s guide to smart sunscreen use

From what the new labels mean to how to properly apply it, here are the essentials to help keep your skin healthy in the sun.