Sunscreen is a summertime must. It protects against ultraviolet light exposure that has been linked to skin cancers, as well as changes commonly associated with aging. Because of these proven benefits, sunscreen has remained largely uncontroversial for much of its nearly century-long history.
In recent years, however, chemicals found in the vast majority of sunscreen have come under scrutiny by the U.S. Food and Drug Administration (FDA) and others. While the subject still needs further study, concerns include ingredients making their way into the bloodstream, possible hormonal effects on humans—especially in young people—and the potential degradation of coral reefs when certain sunscreens make it into the ocean. A committee at the National Academies of Sciences is exploring some of these health and safety questions and is expected to release a report in the coming months.
Here’s what experts say is the healthiest approach to sun protection.
How does sunscreen work?
There are two basic types of sunscreen: physical and chemical.
Physical sunscreens, which are also known as mineral sunscreens, sit on top of the skin and block UV rays. “They are instantaneously effective,” says Dr. Julie Karen, a dermatologist and spokesperson for the Skin Cancer Foundation; users don’t have to wait the 15 minutes or so that chemical sunscreens require before the ingredients offer full protection. There are also only two active ingredients in physical sunscreens—zinc oxide and titanium dioxide—and these are generally good for sensitive skin, she says.
The main downside of physical sunscreen, Karen explains, is that it can leave a chalky or pasty appearance on the skin. Chemical sunscreen solves that issue because it is absorbed into the skin, where it then absorbs ultraviolet light and converts it to non-damaging heat. There are currently about 16 chemical blockers approved for use in the United States, and many more than that in other countries.
“The chemical sunscreens are much more elegant,” says Karen, though both can be effective at blocking short- and long-wave ultraviolet light.
Which sunscreen is safest?
Many dermatologists say that the best sunscreen is the one people will tolerate and actually use. But there are open questions about the human and environmental health impacts of chemical sunscreens.
The chemical that has perhaps garnered the most attention is oxybenzone. “That is the one that is shown to have the most penetration,” says Dr. Henry Lim, a dermatologist at the Henry Ford Medical Center and former president of the American Academy of Dermatology. “And it’s the one that’s been shown to have the most environmental effect.”
In a 2020 study published in the Journal of the American Medical Association, FDA researchers studied six active ingredients in chemical sunscreens—oxybenzone, avobenzone, octocrylene, homosalate, octisalate, and octinoxate—and found that the skin absorbed all of the chemicals at “concentrations that surpassed the FDA threshold for potentially waiving some of the additional safety studies for sunscreens,” the study authors wrote. “While additional data are needed, results showed that all six active ingredients were absorbed into the body’s bloodstream—even after a single use,” the FDA wrote of the findings, and “once absorbed, these active ingredients can remain in the body for extended periods of time.” Other studies have shown that oxybenzone can affect hormone production, though many of those look at relatively high concentrations in rats. However, the FDA continues to consider products with all of these chemicals safe.
“The FDA has reiterated that absorption does not equal risk and advises for the continued use of sunscreen while they work with industry to study the issue,” says Karen. But, she emphasizes, “if you are concerned about oxybenzone for any reason, I recommend choosing a sunscreen without it.”Oxybenzone also has an impact on the health of the ocean, says Katie Day, environmental science and policy manager at the Surfrider Foundation, a nonprofit organization focused on protecting beaches and water. When the chemical is exposed to ultraviolet light, it can lead to coral bleaching. One study published in the Archives of Environmental Contamination and Toxicology in 2016, found that it “poses a hazard to coral reef conservation and threatens the resiliency of coral reefs to climate change.” The National Oceanic and Atmospheric Association lists oxybenzone among ten chemicals found in sunscreen that “can harm marine life.”
In 2018, Hawaii became the first state to ban the sale of sunscreens containing oxybenzone and octinoxate. Other places, from Key West, Florida, to the U.S. Virgin Islands, have followed suit with similar or even more restrictive bans.
In 2019, the FDA requested more research from sunscreen manufacturers, and the National Academies of Sciences also has a committee looking into effects of chemical sunscreens. Day, however, isn’t waiting for the results to tell people to avoid chemical sunscreens. “I would advise against their use completely,” she says.
What to know about benzene
In 2021, the Internet was abuzz with headlines questioning the safety of sunscreen. The impetus was the discovery of the cancer-causing chemical benzene in certain sunscreens, which were mostly sprays. The online pharmacy and lab Valisure tested nearly 300 batches on sunscreen from more than five dozen manufacturers and found that 27% of them contained the carcinogen, even though benzene was not a listed ingredient. Some manufacturers, such as Johnson & Johnson and Coppertone, issued voluntary recalls for their products.
“The contamination may be related to inactive ingredients in drugs such as carbomers (thickening agents), isobutane (a spray propellant), or other drug components made from hydrocarbons (chemicals made of hydrogen and carbon),” the FDA wrote on its website. Karen stresses that the issue was not inherent to sunscreen, but rather a manufacturing problem that companies have taken steps to correct. “This should not make people fearful of sunscreen,” she says.
What sunscreen should I use if I’m concerned?
Lim tells his patients that all approved sunscreens are safe to use, but that anyone who is concerned about the health or environmental impacts of particular chemicals must carefully read the label’s ingredient list. Even the term “reef safe” can’t be taken at its word because it’s unregulated, he says.
“It’s simpler and more practical to go with mineral sunscreen,” he says, which does not contain any of the chemical filters. Day agrees and also recommends looking for the label “broad spectrum,” because it will provide protection against the widest range of ultraviolet light.
Experts add that sun management starts even before a person’s choice of sunscreen. People should seek out shade and wear long, light clothing as well as wide-brimmed hats, saving sunscreen for the areas that are still exposed. Then, they should make sure to continue to reapply every couple of hours when exposed to the sun—and Karen, Day, and Lim all expressed an aversion to spray sunscreens, which can be difficult to properly apply and run the risk of unintended inhalation during application.
“Sun protection is a total package,” says Lim. “Sunscreen is an important component, but not the only component.”
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