Sunscreen is a unique body care product: consumers are directed to apply a thick coat over large areas of the body and reapply frequently. Thus, ingredients in sunscreen should not be irritating or cause skin allergy, and should be able to withstand powerful UV radiation without losing their effectiveness or forming potentially harmful breakdown products. Sunscreens commonly include ingredients that act as “penetration enhancers” and help the product adhere to skin. As a result, many sunscreen chemicals are absorbed into the body and can be measured in blood, breast milk and urine samples.

Active ingredients in sunscreens come in two forms, mineral and chemical filters. Each uses a different mechanism for protecting skin and maintaining stability in sunlight. The most common sunscreens on the market contain chemical filters. These products typically include a combination of two to six of these active ingredients: oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate. Mineral sunscreens use zinc oxide and/or titanium dioxide. A handful of products combine zinc oxide with chemical filters.

Lab studies indicate that some chemical UV filters may mimic hormones or cause skin allergies, which raises important questions about unintended effects on human health from frequent sunscreen application. The most worrisome is oxybenzone, added to nearly 70 percent of the non-mineral sunscreens in EWG’s 2016 sunscreen database.

The Centers for Disease Control and Prevention has detected oxybenzone in more than 96 percent of the American population, based on a representative sampling of children and adults (Calafat 2008). Participants who reported using sunscreen have higher oxybenzone exposures (Zamoiski 2015). Oxybenzone can cause allergic skin reactions and may disrupt hormones (Rodriguez 2006, Krause 2012).

Americans’ exposures to oxybenzone appear to be increasing over the past decade, based on analysis of CDC’s multi-year NHANES study (Han 2012). Investigators at UC Berkeley recently reported a dramatic drop in teen girls’ exposure to oxybenzone and other ingredients of concern in cosmetics when they switched from their usual products to replacements that did not contain those chemicals (Harley 2016).

EWG recommends that consumers avoid sunscreens with oxybenzone. But other chemical filters show similar indications of hormone disruption or skin allergy. Two European studies have detected oxybenzone and other sunscreen filters in mothers’ milk, indicating that the developing fetus and newborns may be exposed to these substances A 2010 study of Swiss mothers by Margaret Schlumpf of the University of Zurich found at least one sunscreen chemical in 85 percent of milk samples.

Experts caution that the unintentional exposure to and toxicity of active ingredients erode the benefits of sunscreens (Krause 2012, Schlumpf 2010). But most conclude that more sensitive tests are needed to determine whether sunscreen chemical ingredients pose risks to users (Draelos 2010, Gilbert 2013).

Dr. Lawrence Jaeger is a board certified dermatologist who has a practice in New York. Dr Lawrence Jaeger specializes in the treatment of all skin, hair and nail disorders including all skin growths.