JAMA Study Shows Sunscreen Chemicals Are Absorbed Into the Bloodstream

As we warned nearly two years prior to the publication of this study, emerging scientific evidence suggested that many of the active ingredients used in sunscreens may penetrate the skin and enter systemic circulation. A study conducted by FDA scientists and published in the published in the Journal of the American Medical Association (JAMA)¹ confirmed that this is exactly what occurred when this question was put to the test. Read on to find out why this is important to your health.

The specific active ingredients evaluated in the study were: avobenzone, oxybenzone, octocrylene, and ecamsule. Commentary provided by JAMA editors offered additional important context: “The authors found evidence of measurable systemic absorption of all 4 sunscreen ingredients at levels meeting the US Food and Drug Administration (FDA) guidelines to trigger a requirement for further systemic safety testing.”² In other words, by the FDA’s own standards, these ingredients reached levels that warrant additional safety evaluation beyond what is typically required for topical over-the-counter products.

Here is a key insight from the JAMA commentary, which we believe also applies more broadly to many personal care products: “Sunscreen users reasonably presume that companies that manufacture and sell sunscreens have conducted basic studies to support the safety and effectiveness of their products and that the medical profession would demand high-quality evidence. However, sunscreens have not been subjected to standard drug safety testing, and clinicians and consumers lack data on systemic drug levels despite decades of widespread use.” […]
These concerns are not new. As far back as 2014, a public advisory panel convened by the FDA concluded that “insufficient evidence existed to confirm the safety of many sunscreen ingredients and formulations.”³

This study was also summarized in a more approachable article published on Wired.com, which provides additional historical and regulatory context. For example, the Wired article notes that many sunscreen active ingredients were originally approved decades ago, before the possibility of meaningful systemic absorption was fully considered under modern testing standards. Also from the Wired article:

“Everyone had always thought that because these are intended to work on the surface of the skin that they wouldn’t be absorbed, but they are,” says Theresa Michele, director of the FDA’s division of nonprescription drug products and coauthor on the FDA-funded study. Her team found that it took only a few hours after application for these chemicals to enter the bloodstream and reach concentrations above the FDA threshold that triggers further safety testing.

“They discovered that while it took only a few hours for the UV-blocking chemicals to exceed the target threshold, for three of the four formulations, those levels remained elevated through the end of the study—three days after participants had ceased applying the products.”

However, where we diverge from the conclusions of both the Wired article and the JAMA commentary is in how this systemic exposure is interpreted. While they emphasize the need for additional data before drawing conclusions about harm, there is already a substantial body of research demonstrating that several of these compounds exhibit biological activity consistent with endocrine disruption and other adverse effects in experimental models. The difference in interpretation is not the absence of evidence, but how that evidence is weighed. Regulatory agencies tend to require large-scale, long-term human data before making definitive safety determinations, whereas we believe the existing evidence raises sufficient concern to warrant a more cautious approach.

Importantly, these concerns have not been resolved in the years since this study was published. The FDA has continued to acknowledge significant gaps in safety data for many commonly used sunscreen active ingredients, particularly regarding systemic absorption and long-term health effects. In subsequent regulatory updates, the agency has reiterated the need for additional data to determine whether these ingredients can be considered generally recognized as safe and effective (GRASE).⁴ In other words, despite decades of widespread use, the question of systemic safety for several of these compounds remains open.

Situations like this are not without precedent. In many areas of public health, early signals of potential harm are often met with uncertainty, debate, and a demand for more data before action is taken. While this cautious approach is understandable, it can also result in prolonged periods where widespread exposure continues despite unresolved safety questions. In this case, hopefully it does not take years for regulatory agencies to fully evaluate and respond to the implications of these findings.

So what potential harm could these sunscreen active ingredients be causing?

Below are just a few examples of studies available in PubMed demonstrating that several of these compounds exhibit biological activity consistent with endocrine disruption and other potential adverse effects.

Avobenzone, which is perhaps one of the most commonly used non-mineral “UV filter” sunscreen ingredients, has demonstrated anti-androgen activity in in vitro studies⁵. This means it can interfere with androgen (male hormone) signaling pathways under experimental conditions. While these findings do not directly establish effects in humans, they raise important questions about potential hormonal impacts that warrant further investigation. We have published a separate article discussing the broader issue of chemical influences on hormone function and male reproductive health.

Animal studies have shown that octocrylene exhibits both antiandrogenic and antiestrogenic activity⁶. In other words, it has the potential to interfere with normal hormone signaling pathways in both males and females under experimental conditions.

Additional animal studies have demonstrated that homosalate and several other “UV filter” sunscreen ingredients can antagonize (block) the androgen receptor⁷, further supporting concerns about endocrine-disrupting activity within this class of compounds.

Oxybenzone has been shown to exhibit estrogenic activity and has been associated with adverse effects on reproductive systems in animal models⁸. In addition to these biological concerns, oxybenzone has also been linked to environmental damage, particularly to coral reef ecosystems, which contributed to restrictions on its use in places such as Hawaii.

This is not solely an animal or environmental concern. The Environmental Working Group (EWG) provides a useful summary of research on sunscreen ingredients, including human exposure data. For example, in an analysis of CDC-collected biomonitoring data, researchers found that adolescent boys with higher oxybenzone levels had significantly lower total testosterone concentrations⁹. While this type of observational data does not establish causation, it adds to a growing body of evidence suggesting potential endocrine-related effects in humans.

Compared to other sunscreen active ingredients, there is relatively limited publicly available research on ecamsule, a newer compound in the sunscreen industry that has historically been protected under patent. This lack of widespread toxicological data in the public literature does not indicate that the compound is either safe or harmful, but rather that there is insufficient information available to make a well-supported determination.

Some studies have suggested that ecamsule may be susceptible to photodegradation when exposed to UV radiation¹⁰, which could impact its stability and duration of effectiveness under real-world conditions. Taken together, the combination of limited safety data and questions regarding stability highlights a broader issue: absence of evidence should not be interpreted as evidence of safety. Until more comprehensive data are available, a degree of uncertainty remains regarding both the safety and long-term performance of this ingredient.

For the FDA and JAMA editors to conclude that there is insufficient evidence to determine harm highlights a fundamental gap between emerging scientific evidence and the level of proof required for regulatory action. A substantial body of research already demonstrates biological activity and potential adverse effects associated with several of these compounds. The issue is not that evidence is absent—it is that it does not yet fit neatly within the framework required for definitive regulatory conclusions.

In the meantime, widespread exposure continues. That reality makes it all the more important for individuals to take an active role in understanding the products they use. Read both active and inactive ingredients carefully, and choose products from companies that prioritize transparency and safety. Our Shield SPF15 sunscreen is formulated with this approach in mind, but there are certainly other options available. The key is to make informed decisions rather than assuming safety has already been fully established. 

For Health, 

Rob