Summer is almost here, which means it’s time for picnics, pool parties, and every parent’s favorite pastime: chase-after-your-kid-with-the-sunscreen-bottle. But what’s arguably more arduous than slathering lotion onto a screaming 3-year-old is picking out the right sunscreen at the store. Not only are we presented with hundreds of choices—does your child prefer a cool mist of oily sunscreen or a squirt of lotion? Does she have sensitive skin or extra sensitive skin? SPF 30, 50, or 75?—many are apparently unsafe, too. Some warn that sunscreens can cause cancer while others claim that certain ingredients increase the risk of infertility. Dr. Oz says your sunscreen might be poisonous. In its 2013 Guide to Sunscreens, the nonprofit Environmental Working Group says that only 25 percent of sunscreens on the market are “free of ingredients with serious safety concerns.” So should we keep our kids indoors for the next three months?
There is some scientific evidence to support the safety risks, but it’s hardly conclusive. And many media outlets have overinterpreted research results, making broad statements that don’t reflect what scientists actually know. (Perhaps you have seen these statements on your Facebook feed?) Plus, while there is research to support steering clear of controversial ingredients like oxybenzone and retinyl palmitate—the Environmental Working Group’s guide is an excellent resource for identifying sunscreens without them—some experts warn that other sunscreen compounds could pose similar risks we don’t yet know about, because only a few compounds have been extensively studied.
It helps to have a short primer on sunscreen and how it works. By far the most popular sunscreens are the “organic” ones, so-called because they contain carbon, not because they were grown without pesticides or on a free-range farm. These include most Coppertone and Banana Boat products. These sunscreens protect us from harmful ultraviolet (UV) radiation by absorbing rays before they penetrate deep into our skin. (Not all organic sunscreens absorb both UVA and UVB rays, which have different wavelengths, so it’s important to pick “broad spectrum” versions that protect against both types.) Inorganic “mineral” sunscreens, on the other hand, are typically comprised of coated titanium dioxide or zinc oxide molecules or a combination of the two. These formulations, which can be found in Badger and California Baby products, typically protect against UVA and UVB light by reflecting or scattering the rays.
Organic sunscreens often contain oxybenzone, and one of the most well-publicized claims about oxybenzone, which is also an ingredient in some cosmetics and in plastic food packaging, is that it acts as a hormone disruptor, tweaking natural hormone levels in ways that could potentially be harmful. A 2008 study found traces of oxybenzone in the urine of 96.8 percent of a representative sample of the U.S. population, which suggests that the molecule is widely used and that it’s absorbed into the body after being applied onto the skin. But how confident can we be that its hormone-changing effects are actually harming us? Most studies have been conducted on cells or animals and are difficult to draw conclusions from—one study, for instance, found uterine changes in rats that were fed extremely high doses of oxybenzone and other organic sunscreens, but people don’t typically eat sunscreen for lunch, so it’s hard to know whether these products pose the same risks to us as we use them.
One 2004 intervention study was, however, conducted in humans. Researchers repeatedly measured blood hormone levels in 32 people before and after they applied lotion that contained two commonly used organic U.S. sunscreen ingredients. The subjects’ blood levels of several hormones, including testosterone, changed after using the lotion. But the hormone differences were found only at certain points of time after lotion application and not others, which led the researchers to conclude that the changes “did not seem to be related to the exposure to sunscreen compounds.” Huh.
Organic sunscreens have another potential downside: When they absorb UV light, they become “excited” and unstable. Research has shown that the common sunscreen ingredients oxybenzone, octocrylene, and octylmethoxycinnamate (OMC) dissipate that extra energy in ways that lead to the production of molecules called reactive oxygen species that could damage the lower layers of skin and our DNA. This finding is quite ironic, because UV light is thought to increase the risk of cancer and accelerate aging in part because it does the exact same thing. You cannot win.
To put these findings into perspective, keep in mind that UV light also produces these damaging molecules after penetrating unprotected skin. And researchers argue that if you re-apply sunscreen, as you’re supposed to, these potentially damaging effects of reactive oxygen species could be mitigated, because re-application prevents UV rays from reaching the sunscreen molecules that have penetrated deepest into the skin. Sunscreen manufacturers also try to optimize their formulations so that they stay on the surface of the skin rather than penetrating deep as they did in some of these experiments.
Some sunscreen companies add antioxidants like vitamin E and vitamin C to their formulations as well to absorb some of these reactive compounds. One 2011 study found that the addition of antioxidants to SPF 15 or 50 sunscreen formulations reduced the numbers of reactive oxygen species in skin more than two-fold. (To find sunscreens with added antioxidants, look for inactive ingredients such as sodium ascorbyl phosphate, tocopherol, tocopheryl acetate or diethylhexyl syringylidenemalonate.)