The trouble with ingredients in sunscreens

Sunscreen products are intended to be applied to the body every day, for a lifetime. The companies that make and sell sunscreen ingredients and products should test them thoroughly for potential short-term and long-term health effects. This includes toxicity testing for irritation and skin allergies, as well as testing for skin absorption and the potential to cause cancer, disrupt the hormone system and cause harm during reproduction and development.

In 2019, when the federal Food and Drug Administration – the agency that governs sunscreen safety – proposed its most recent updates to sunscreen regulations, it found that only two ingredients, zinc oxide and titanium dioxide, could be classified as safe and effective, based on the currently available information. But in the past year, numerous new studies have raised new concerns about endocrine-disrupting effects from three other ingredients: homosalate, avobenzone and oxybenzone.

Within the past year, the European Commission has published preliminary opinions on the safety of three organic UV filters, oxybenzone, homosalate and octocrylene. It found that the levels of two of them were not safe in the amounts at which they are currently used, and proposed a concentration limit of 2.2 percent for oxybenzone and 1.4 percent for homosalate. U.S. sunscreen manufacturers are legally allowed to use these two chemicals at concentrations up to 6 and 15 percent, respectively, and hundreds of sunscreens manufactured in the U.S. use them at concentrations that far exceed the European Commission’s recommendations.

The ingredients oxybenzone, octinoxate, octisalate, octocrylene, homosalate and avobenzone are all systemically absorbed into the body after one use (Matta 2019, Matta 2020), according to studies published by the FDA, which also found that they could be detected on the skin and in the blood weeks after no longer being used (Matta 2020). Previous studies detected many sunscreen ingredients in breast milk and urine samples (Schlumpf 2008, Schlumpf 2010). In addition, it’s possible for sunscreen users to inhale ingredients in sunscreen sprays and ingest some of the ingredients they apply to their lips, so the ingredients must not be harmful to the lungs or internal organs.

This constant exposure to sunscreen chemicals raises concerns, especially because there is not enough safety data for most ingredients. We have even more concerns about ingredients such as oxybenzone, which have been linked to hormone disruption by numerous studies.

Active ingredient toxicity

This table outlines human exposure and hazard information for eight common FDA-approved sunscreen chemicals, often referred to as active ingredients because they provide ultraviolet, or UV, protection. Sunscreen products typically include a combination of active ingredients, except for those formulated with zinc oxide.

Chemical	FDA 2019 proposed classification as safe and effective	Skin penetration	Hormone disruption	Skin allergy and or other concerns
Oxybenzone	No	+	+	+
Octinoxate (Octyl methoxycinnamate)	No	+	+	+
Homosalate	No	+	+	+
Octisalate	No	+	–	–
Octocrylene	No	+	–	+
Avobenzone	No	+	+	+
Titanium dioxide	Yes	–	–	Inhalation concerns
Zinc oxide	Yes	–	–	Inhalation concerns

+ = evidence; – = no or weak evidence

The science on ingredient toxicity

Oxybenzone

The most worrisome sunscreen active ingredient is oxybenzone, according to publicly available scientific research. It is readily absorbed through the skin (Matta 2019, Matta 2020) and the Centers for Disease Control and Prevention found it in nearly all Americans, with higher levels in those who report applying sunscreen (Zamoiski 2016). Oxybenzone causes allergic skin reactions (Rodriguez 2006), behaves like an endocrine disruptor in many studies (Krause 2012, Ghazipura 2017) and is potentially of greater harm to children (FDA 2019).

In an evaluation of CDC-collected exposure data for American children, researchers found that adolescent boys with higher oxybenzone measurements had significantly lower total testosterone levels (Scinicariello 2016). Three other studies reported statistically significant associations between oxybenzone exposure during pregnancy and birth outcomes. One reported shorter pregnancy in women carrying male fetuses, two reported higher birth weights for baby boys and one found lower birth weights for baby girls (Ghazipura 2017). Female exposures to oxybenzone and related chemicals have been linked to an increased risk of endometriosis (Kunisue 2012).

According to the latest proposed FDA sunscreens monograph, the agency needs further data to determine whether oxybenzone can be considered safe and effective, since:

[the] available literature … indicat[es] that oxybenzone is absorbed through the skin to a greater extent than previously understood and can lead to significant systemic exposure.… The significant systemic availability of oxybenzone … is a concern, among other reasons, because of questions raised in the published literature regarding the potential for endocrine activity.

Four studies published in 2020, after the FDA released its draft proposal, support previous findings that oxybenzone can act as an endocrine disruptor and may increase the risk of breast cancer and endometriosis (Kariagina 2020, Peinado 2020, Rooney 2020, Santamaria 2020). In addition, the National Toxicology Program found equivocal evidence of carcinogenicity in rats after observing increases in thyroid tumors and uterine hyperplasia in females with high exposure to oxybenzone (NTP 2020).

Investigators at the University of California at Berkeley reported a dramatic drop in teen girls’ exposure to oxybenzone in cosmetics when they switched from their usual products to replacements that did not contain this chemical (Harley 2016).

Recently, the European Commission found current human exposure levels to oxybenzone to be unsafe and proposed a concentration restriction of 2.2 percent (SCCS 2020) – lower than the limited amount allowed in U.S. sunscreens, which is up to 6 percent. Several countries ban the sale of sunscreens that contain this ingredient, because it may be harmful to aquatic life.

EWG recommends that consumers avoid sunscreens with oxybenzone.

Octinoxate (Octyl methoxycinnamate)

Octinoxate is an organic UV filter. It is readily absorbed into the skin and continues to be absorbed after the sunscreen has been applied. It has been found in blood 16 times above the proposed FDA safety threshold (Matta 2019, 2020). Animal studies have shown the chemical has hormone effects on the metabolic system and affects thyroid hormone production (Seidlova-Wuttke 2006), with some evidence for other endocrine targets, including androgen and progesterone signaling (Krause 2012). Octinoxate can also cause allergic reactions after exposure to ultraviolet light (Rodriguez 2006).

Several countries ban the sale of sunscreens made with octinoxate, because they may be harmful to aquatic life.

Homosalate

Homosalate is an organic UV filter widely used in U.S. sunscreens. The FDA has proposed that there is insufficient data to evaluate whether it is safe and effective to use in sunscreens. Homosalate has been found to penetrate the skin, disrupt hormones and produce toxic breakdown byproducts over time (Krause 2012, Sarveiya 2004, SCCNFP 2006, Matta 2020).

A recent opinion from the European Commission found that homosalate was not safe to use at concentrations up to 10 percent and recommended a maximum concentration of 1.4 percent, because of concerns for potential endocrine disruption (SCCS 2020). The FDA allows U.S. sunscreen manufacturers to use it in concentrations up to 15 percent.

Octisalate

Octisalate, an organic UV filter, readily absorbs through the skin at levels 10 times more than 0.5 nanograms per milliter, the FDA’s cutoff for systemic exposure. This cutoff is the maximum concentration that may be found in blood before there are potential safety concerns. The FDA has requested additional safety testing when a sunscreen is absorbed above this level (Walters 1997, Matta 2020).

The FDA 2019 proposed update suggests there is insufficient data to determine whether octisalate can be classified as safe and effective to use in sunscreens (FDA 2019). A case report showed that the chemical has been linked to allergic contact dermatitis (Singh 2007). Analysis of high throughput screening assays by the Environmental Protection Agency suggests octisalate may have endocrine effects, weakly binding to the estrogen receptor.

Octocrylene

Octocrylene readily absorbs through the skin at levels about 14 times the FDA cutoff for systemic exposure (Hayden 2005, Matta 2020), but the agency suggested there is insufficient data to determine whether it can be classified as safe and effective (FDA 2019).

Studies have found that octocrylene causes relatively high rates of skin allergies (Bryden 2006). It has been linked to aquatic toxicity, with the potential to harm coral health (Stein 2019), and it is often contaminated with the known carcinogen benzophenone. According to a recent study, its levels can increase when it is stored (Downs 2021). The European Commission recently concluded that although there was some evidence of octocrylene’s endocrine-disrupting potential, current use concentrations up to 10 percent were considered safe.

Avobenzone

Avobenzone is a widely used organic filter that provides protection from UVA rays and is often used with other organic active ingredients in products offering broad spectrum protection.

Because avobenzone is not stabile, it must be paired with other ingredients that act as stabilizers to prevent it from breaking down in the sun. Breakdown products of avobenzone can cause allergic reactions (Nash 2014). Avobenzone can disrupt the endocrine system and has been shown to block the effects of testosterone in cellular studies (Klopcic 2017).

In one study, avobenzone was detected in serum samples at levels nine times above the FDA's cutoff for systemic exposure (Matta 2020).

Titanium dioxide and zinc oxide

Mineral sunscreens are made with titanium dioxide and zinc oxide, usually in the form of nanoparticles. The FDA proposed that both titanium dioxide and zinc oxide be classified as safe and effective. Evidence suggests that few if any zinc or titanium particles penetrate the skin to reach living tissues (Gulson, 2012, Sadrieh 2010).

Titanium dioxide is classified as a possible human carcinogen by the International Agency for Research on Cancer, because of the potential of exposure through inhalation. For this reason, powdered or spray formulations containing titanium dioxide are of concern. Zinc oxide also carries inhalation concerns when used in spray and powder products

In general, mineral sunscreens tend to rate better than chemical sunscreens in the EWG sunscreen database. However, it is important that manufacturers use forms of minerals coated with inert chemicals to reduce photoactivity. To minimize the risks to sunscreen users and maximize these products’ sun protection, EWG supports stronger guidelines and restrictions on the types of used zinc and titanium in sunscreens. Our detailed analysis of nanoparticles in sunscreens is available here.

Other active ingredients

Mexoryl SX, an uncommon active ingredient in U.S. sunscreen, offers strong UVA protection. The FDA’s analysis indicated there was insufficient data to classify the ingredient as safe and effective. Public research provides no evidence of hormone disruption and rare incidence of skin allergy.

Aminobenzoic acid, or PABA, and trolamine salicylate are active ingredients that are no longer commonly used in U.S. sunscreens. The FDA’s 2019 proposal concluded that the risks of these chemicals outweigh their benefits and proposed classifying them as unsafe.

Inactive ingredients

The FDA should look closely at the so-called inactive ingredients in sunscreens, which typically make up half to 70 percent of a sunscreen. EWG recommends the FDA launch a thorough investigation of the safety of all sunscreen ingredients to ensure that none of them damages skin or causes other health harms.