Concern: “Why does the message on the bag from my yoga clothing store say that sunscreen absorbed into skin might be worse than sunshine?”
Some of Lululemon’s tote bags are emblazoned with that message, followed by “Get the right amount of sunshine.” The statement lacks details, but we looked into the science. Three chemicals (and possibly others) commonly used as UV filters in sunscreens have been shown to cause ROS (reactive oxygen species) to generate. Kerry Hanson, a senior research chemist at University of California, Riverside, who researches sunscreen and ROS, explains that we produce ROS in our bodies both naturally and upon exposure to UV light, to help signal important biochemical processes. “The bad side of ROS is that they also react with cellular components like cell membranes or collagen and possibly with DNA. Over a lifetime, this could potentially increase the oxidative load on the skin, and lead to skin damage.”
The UV filters in sunscreen studied by Hanson and shown to cause ROS to generate were oxybenzone and octylmeth-oxycinnamate (primarily used to block UVB rays, which penetrate the outer layer of skin and are responsible for most skin cancers and cataracts), and octocrylene (used to stabilize avobenzone, one of the only UV filters approved by governments to filter UVA). UVA rays have longer wavelengths and are more prevalent than UVB; UVA also plays a role in certain skin cancers. (This is why you should choose sunscreens labelled “broad spectrum” or “UVB/UVA”; otherwise, you are protected only from UVB rays.) But there is a huge caveat when it comes to ROS production: “Certain conditions must be met before the molecules in any chemical can generate it,” says Hanson. “Those conditions include the molecule penetrating the skin, and then UV light reaching that molecule.”
You can prevent ROS from being generated if you reapply sunscreen every two hours, says Hanson, citing the Skin Cancer Foundation guidelines. Consistent reapplication ensures that UV light will not reach the molecule because there is a constant coating of UV filters on the top layer of your skin, she says (important, since it is known that UV filters can penetrate into skin).
The goal of sunscreen formulators, Hanson adds, is to find a formula that “acts more like latex paint on a wall, and just sits on the surface of the skin.”
Bottom Line: So is absorption of sunscreen putting you in danger? The amount of chemical that penetrates the skin varies by individual because skin barrier properties are different from person to person. “It’s important to emphasize that the FDA deems UV filters to be safe [so does Health Canada], and when used correctly they prevent sunburns that can lead to potentially deadly skin cancer,” says Hanson.