Mineral bases like zinc oxide, on the other hand, are natural and even healthy. (In fact, we need zinc for normal everyday health and function.) Studies show that zinc oxide tops the list for broad-spectrum protection. So what are the main culprits to be wary of?
The most common active ingredient in chemical-filter sunblocks penetrates the skin, going straight into the bloodstream. It can trigger allergic skin reactions, act like estrogen in the body, and has been linked to endometriosis.
Octinoxate, Homosalate + Octocrylene
These widespread chemicals have been found in mother’s milk. Octinoxate has been shown to cause thyroid and behavioral alterations in animals. Homosalate disrupts such hormones as estrogen, androgen, and progesterone. And octocrylene shows high rates of skin allergy.
This widespread ingredient is the best for filtering skin-damaging UVA rays, but it must be stabilized with other chemicals (most commonly octisalate). Used alone, it will break down when exposed to sunlight. Peterson considers this one “the best of the worst” when it comes to chemical filters.
Unlike zinc, our bodies aren’t conditioned to break down this titanium dioxide that might be absorbed through the skin. Titanium dioxide raises the SPF of products but breaks down more easily than zinc oxide when exposed to light.
Non nano (original form found in nature) is best when it comes to titanium dioxide; watch out for the powdered version of this ingredient, which is highly controversial because of inhalation risks.
In addition to potentially toxic active ingredients, it’s wise to check product labels for certain red-flag inactive ingredients (which can make up more than half of a sunscreen product). Retinyl palmitate, a vitamin A derivative, is one you want to look out for, as it can promote tumor growth on skin when exposed to the sun, according to government studies. It also goes by the names of retinyl acetate and retinyl linoleate. (Retinol, or whole molecule vitamin A, on the other hand, has beneficial anti-aging properties and may help prevent cancer but should be used at night or with very limited sun exposure.)
While research about the potentially harmful effects of ingredients in sunscreen is still very much in its infancy, it’s still wise to be a smart shopper and know what you’re putting on your skin. After UVB and UVA protection, the third defense against sun exposure is antioxidant support. “Sunscreens with antioxidants are great because they eat up the free radicals that cause inflammation from the sun,” Peterson says. She recommends avoiding citrus oils, which can photosensitize the skin, and looking instead for ingredients such as green tea oil, red raspberry seed oil, green and white tea, and astaxanthin (a beneficial carotenoid found in microalgae). With so many sunscreen options, it’s hard to know where to begin. For starters, try Elemental Herbs’ coconut sunscreen stick (SPF 30), which provides good UVA protection, is a low health risk, and tops the list of the Environmental Working Group’s best sunscreens. Shopping for natural products is ideal, but remember to not to rely solely on sunscreen to protect yourself. First and foremost, you want to cover up, seek shade, and plan outdoor activities when the sun isn’t at its strongest.