We all know that sunscreen is important. But there’s plenty of confusion about it, starting with that SPF (sun protection factor) label: Is a higher SPF always better?
Not necessarily. Once SPF goes over 30, the increase in protection is negligible, according to the Skin Cancer Foundation. But in recent years, sunscreen manufacturers have been in an arms race, marketing products with SPFs of 70 or 100 or even higher. Unfortunately, high SPFs can give people a false sense of security.
SPF refers primarily to a sunscreen’s ability to block the sun’s ultraviolet-B (UVB) radiation, the main cause of non-melanoma skin cancer and sunburn; ultraviolet-A (UVA) is mostly responsible for skin aging but also contributes to skin cancer. When properly applied, a product with SPF 15 blocks 93 percent of UVB; SPF 30 blocks 97 percent; SPF 50 blocks 98 percent; SPF 100 blocks 99 percent.
Super-high SPF products may block more UVB than UVA. Thus, they are better at preventing sunburn than lower SPFs. This was seen in a recent study in the Journal of the American Academy of Dermatology, which found that use of sunscreen with SPF 100 resulted in half as much facial sunburn as one with SPF 50. But super-high products don’t necessarily reduce other kinds of skin damage besides sunburn. And because people using them aren’t turning red, they may think they’re fully protected and thus may stay in the sun longer or re-apply the sunscreen less often.
Even apart from SPF, sunscreen labeling has long been confusing. But things have improved, thanks to 2011 FDA guidelines that made the labels uniform and banned misleading terms.
The term “broad-spectrum” ensures that a sunscreen protects against both UVA and UVB. Products must pass the FDA’s standardized test to be labeled with this term. Broad-spectrum sunscreens with SPF of 15 or higher may state that, besides reducing sunburn, they decrease the risk of skin cancer and early aging when used with other sun-protective measures (such as wearing a hat and protective clothing). Higher SPF values on broad-spectrum sunscreens indicate greater protection against both UVA and UVB. Sunscreens that are not broad-spectrum, or are broad-spectrum but have SPFs below 15, must carry an alert that they only help prevent sunburn, not skin cancer or early skin aging.
“Water-resistant” means the sunscreen is effective for a specified time—40 or 80 minutes, as listed—while you’re swimming or if you sweat a lot, after which it needs to be reapplied. If it doesn’t say water-resistant, reapply more often if you swim or sweat.
Here are more facts about how to protect yourself from the sun’s damaging rays—debunking some common myths and misconceptions:
Myth: It doesn't matter how you apply sunscreen.
Fact: The way you apply it makes a big difference. You’re supposed to apply about one ounce—enough to fill a shot glass—to your face and exposed parts of your body, which approximates the amount used in SPF testing. But in the real world, most people use only half as much—that’s what was seen in the previously mentioned study. In addition, sunscreens that chemically absorb UV rays (such as those containing avobenzone or oxybenzone) should be applied at least 15 minutes before going out into the sun. (Sunscreens containing zinc oxide or titanium dioxide don’t need to be applied in advance since they act immediately as a physical sunblock.) Sunscreen should be reapplied every two hours. Failing to apply it evenly can cause you to receive a far lower SPF than advertised.
Myth: People with dark skin can spend more time in the sun without harm.
Fact: Melanin, the compound that colors one’s skin, provides the equivalent of an SPF of about 1.5 to 2, which lowers the risk of skin cancer in people of color. However, this does not eliminate the risk. Because people of color tend to assume they’re naturally protected, they’re often diagnosed with skin cancer when it’s more advanced and potentially fatal. It is essential that people of color use sunscreen to protect themselves from skin cancer, sunburns, and aging.
Myth: Using sunscreen lowers vitamin D levels in your body.
Fact: In order to get your daily Vitamin D, you need to be exposed to the sun for about 15 minutes a day, depending on latitude and season. After the needed amount of time, your body’s production of Vitamin D stops. We do not continuously make and produce Vitamin D every time we are exposed to the sun. If you are unable to get those 15 minutes of exposure a day, some foods with Vitamin D are salmon, tuna, mackerel, cheese, and fortified milk.
Myth: Sunscreens will work at their advertised SPF.
Fact: More than 40 percent of sunscreens tested by Consumer Reports in 2016 fell short of their advertised SPF. Indeed, two sunscreens advertised as having an SPF of 50 actually had an SPF of 8. The good news? Consumer Reports found 17 sunscreens that lived up to their claims, and most are inexpensive and widely available.
Myth: Sunscreen is toxic and puts dangerous chemicals on your skin.
Fact: Some lab studies suggest that chemicals in sunscreens such as oxybenzone may cause skin allergies or mimic hormones, but no studies have convincingly established health problems in people. Meanwhile, it’s well proven that damage from UV rays can cause skin cancer. The FDA considers sunscreen an over-the-counter drug, and thus it is subjected to more scrutiny and testing than cosmetics, fragrances, or creams.
Myth: If you put on sunscreen, you can stay out in the sun longer.
Fact: While a broad spectrum sunscreen with SPF of 15 or above protects against sunburns, it does not protect you from all the sun’s damaging rays. No sunscreen can block all UV rays. Plus, regardless of the SPF, sunscreen is effective for only about two hours (unless reapplied). The American Academy of Dermatology recommends that you wear protective hats and clothing to shield your face, arms, and legs from harmful rays.
Myth: SPF is the most important factor to consider when buying sunscreen.
Fact: SPF refers to the sunscreen’s effectiveness against UVB rays, but says nothing about the product’s ability to shield you from UVA rays. Look for the words “Broad Spectrum” on the sunscreen label. That means you’re buying a sunscreen that protects against both UVB and UVA radiation.
Myth: If you sit under a beach umbrella, you don’t need sunscreen since the beach umbrella blocks the sun’s rays.
Fact: Actually, the sand reflects 17% of UV radiation. You still need to wear sunscreen and protective clothing if you’re relaxing under an umbrella on the beach. A 2017 study in JAMA Dermatology found that nearly 80 percent of people who sat under a beach umbrella (6.5 feet diameter) for 3.5 hours without sunscreen had some degree of sunburn the next day, compared to 25 percent of people who used a high-SPF sunscreen and stayed out in the sun. This was despite the fact that the umbrella material allowed no UV to penetrate and the participants in the umbrella group were monitored to ensure that they got no direct sun exposure.
Myth: Having a base tan helps protect your skin.
Fact: A suntan doesn't provide your skin with nearly enough protection. Moreover, the tan itself is a sign of skin damage. (After being hit by UV rays, the cells in your skin produce melanin to prevent greater damage.) In particular, it’s risky to use tanning beds before summer. Tanning beds emit a lot of UVA radiation, which is less likely to burn the skin than UVB, but which penetrates deeper into your skin.
Myth: 80% of my exposure to damaging UV rays occurs before the age of 18.
Fact: Only 25 percent of total UV exposure occurs before the age of 18, according to research conducted by the Skin Cancer Foundation. You’ll protect your skin at any age when you start applying sunscreen and wearing protective clothing.
Originally published July 2016; updated June 2017 and July 2018.
Also see How to Buy the Best Sunscreen.