The Truth About Mineral vs. Chemical Sunscreens
Exploring the science — and lack thereof — behind sunscreen safety
For a 2019 study, researchers at the U.S. Food and Drug Administration had healthy people apply common, commercially available sunscreens.
For four days — and four times each day — the people in the study sprayed or rubbed sunscreen onto their bodies. Most sunscreen labels advise people to reapply “at least every two hours,” so the study was designed to assess what would happen inside the body if people followed this guidance. For example, if someone went on a beach vacation and slathered on sunscreen throughout the day, as directed, what, if anything, might show up in their blood?
To find out, the study team collected blood samples from each of the participants. They measured the samples for “systemic absorption,” or evidence that the active sunscreen chemicals had leached through the skin and into a person’s blood. Per FDA rules, systemic absorption above 0.5 ng/mL necessitates follow-up research to determine whether a chemical could be cancerous or associated with any developmental or reproductive harms.
The blood samples revealed that all three of the common sunscreen chemicals — avobenzone, oxybenzone, and octocrylene — exceeded the 0.5 ng/mL limit, and all three did so within hours of the first application. But really, “exceeded” is too weak a word. For the people who used a sunscreen containing oxybenzone, blood concentrations swelled to roughly 210 ng/mL, or more than 400 times the safety threshold. The results were less dramatic for the other two chemicals, but all of them easily crossed the limit of scrutiny. Even after people stopped applying the sunscreens, all three of the chemicals continued to circulate in their blood for days.
What all this means for human health is unclear; the study team explained that all of these chemicals lack “safety assessment data.” But prior work — some in people, some in animals or lab settings — has linked these chemicals (particularly oxybenzone) to hormone changes, skin allergies, altered birth weights, and other potential health concerns.
These sorts of findings have led many to ditch these “chemical” sunscreens in favor of “mineral” (also known as “physical”) sunscreens, which provide protection from the sun using fundamentally different methods and ingredients.
Are mineral sunscreens safer?
For many, the findings of the study, published in the Journal of the American Medical Association, were both satisfying and frustrating.
Consumer watchdog groups had for years called on the FDA — the regulatory agency that conducted the study and also oversees the safety of consumer products — to take a closer look at the chemicals in sunscreens, many of which have been around for decades. The nonprofit Environmental Working Group (EWG) has led those calls. And they continue to pressure the FDA to restrict the sale of these chemicals until further work can determine whether they’re safe. While some raise eyebrows at the EWG for overstating the risks of certain chemicals, independent experts confirm more research is needed.
“The big question is are these chemicals dangerous? We just don’t know,” says Adam Friedman, MD, a professor and chair of dermatology at George Washington University.
While researchers are sorting that out, he says that people who don’t want to take any risks truly can feel at ease using mineral sunscreens. These usually contain titanium dioxide and zinc oxide, mineral-derived ingredients that offer protection in two ways. First, they scatter ultraviolet (UV) radiation, which is the energy found in sunlight that can damage the DNA and fats in skin cells. This damage can cause tanning or burning in the short term and scarring, wrinkles, and skin cancer in the long term. Along with deflecting this UV energy, Friedman says that mineral sunscreens also absorb UV radiation and therefore restrict its damage.
The big hassle with mineral sunscreens, as most know all too well, is that they tend to coat the skin in a visible layer of white gunk. Product makers have tried to combat this problem by formulating mineral sunscreens that employ incredibly small nanoparticles of titanium and zinc dioxide, which are less visible and easier to spread on the skin. But the size of these particles have raised concerns that they may be able to slip into the skin and bloodstream.
“That’s BS,” Friedman says. While some people freak out a bit when they hear the word “nano,” he says that the research to date has found that mineral sunscreens featuring nanoparticles do not penetrate above the outermost layers of the skin — even when applied to damaged skin.
Choosing a safe sunscreen
While it’s fair for people to wonder and worry, Friedman says that, for now, it’s unclear whether oxybenzone and other “chemical” sunscreen ingredients cause harm when they’re absorbed into the body. “We do know that some of these chemicals can be irritating to diseased skin,” he says. “So for people with acne, psoriasis, eczema, etc., I usually recommend a mineral sunscreen.”
For those who aren’t comfortable using a chemical product whose safety is uncertain, he says mineral sunscreens — including those made using nanoparticles, which is most of them — appear to be safe. “The only concern with these is if you inhale them,” he says. “We don’t know if that’s dangerous, but if you inhale a nanoscale mineral sunscreen, it’s possible that could be an issue.”
When using these products, he recommends spraying them into your palm and then rubbing them onto your skin. This lowers the odds that you’ll inadvertently inhale them, and it also helps ensure you’re applying enough to safeguard your hide from the sun. “I tell people to buy SPF 50 because most people don’t apply enough to get the full SPF labelled on the product,” he says. Also, be sure to buy a product labelled “broad spectrum,” which designates a sunscreen that provides complete UVA and UVB protection.
If you’re shopping for sunscreens, the EWG offers a comprehensive consumer guide.