For decades, dermatologists have encouraged us to slather on the sunscreen before we expose our skin to the sun’s rays. The goal is to prevent premature aging and, more importantly, to reduce the risk of skin cancer.
How much of your sunscreen is absorbed into your body? You might think that question would have been answered decades ago. Surprisingly, we are just learning how much sunscreen passes through your skin and gets into your blood stream. A new study published in JAMA (May 6, 2019) reveals that all four of the ingredients tested resulted in systemic absorption. One in particular, oxybenzone, far exceeded the 0.5 ng/mL level that should trigger toxicological studies.
Everyone LOVES Sunscreen:
Americans are not always good about following public health pronouncements. They are pretty lax about cutting back on salt, washing hands after going to the bathroom or eating lots of vegetables daily. What people ARE good at is slathering on the sunscreen.
Sunscreens produce detectable benefits. You may not see immediate results from eating vegetables or lowering blood pressure, but you know within a few hours the consequences of spending hours in bright sunlight without sunscreen.
A bad sunburn hurts and looks awful. As a result, people are rewarded for regular sunscreen use. Add to that the constant reminders from dermatologists to always use sunscreen. The messages work! Americans spend over $650 million on sunscreen products each year.
Sunscreen Absorption Into Your Body:
Many Americans assume that what they put on their skin stays on their skin. The idea that the chemicals in skin care products penetrate the skin and get into the body seems foreign. But the skin is not an impenetrable barrier. It is truly astonishing that until now, very little research has been conducted on sunscreen absorption.
The FDA has recognized this lapse. In 2018, the agency told the sunscreen industry that it is time to find out whether sunscreen ingredients are absorbed (Guidance for Industry: Nonprescription Sunscreen Drug Products Safety and Effectiveness Data). FDA scientists took the first step with the current study.
How They Did the Study:
The researchers recruited 24 individuals as their study participants and divided them into four groups. Following proper sunscreen application procedures, each volunteer got sunscreen on 75 percent of their skin multiple times a day, just as if they were spending a vacation at the beach. (It was less fun, though, as they were not actually at the beach and did not leave the clinical facility to go out in the sunshine. Instead, they had blood drawn at regular intervals.)
The investigators used two different sunscreen sprays, one lotion and one cream. Each group of volunteers used the same type of sunscreen for the full week of the study.
When the scientists analyzed the blood samples, they found that sunscreen ingredients were detected in the volunteers’ blood within a relatively short time. They wanted to know about avobenzone, which is a primary sunscreen ingredient. Until now, no one knew whether or to what extent avobenzone might be absorbed through the skin. In addition, the investigators considered levels of oxybenzone, octocrylene, and ecamsule.
Oxybenzone has been controversial for years. It is a common ingredient in many sunscreens. According to EWG (the Environmental Working Group, a nonprofit nonpartisan organization), this is among the most worrisome sunscreen ingredients: “Oxybenzone can cause allergic skin reactions (Rodriguez 2006). In laboratory studies it is a weak estrogen and has potent anti-androgenic effects (Krause 2012, Ghazipura 2017)” (https://www.ewg.org/sunscreen/report/the-trouble-with-sunscreen-chemicals/)
What does “potent anti-androgenic effects” mean? Androgens are often called male hormones, but that is a misnomer. Men and women make testosterone. This critical hormone is essential for good health. The idea that a sunscreen ingredient can affect both estrogen AND testosterone is quite disconcerting, especially for young children.
EWG analysts note that:
“In a recent 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).”
“Given the pervasiveness of oxybenzone exposures, further study is needed to evaluate the association between oxybenzone and hormone disruption in children and adults.”
How much oxybenzone is absorbed through the skin? In the new JAMA study, the researchers found significant absorption of oxybenzone. Within two or three days, participants exposed to oxybenzone-containing sunscreens had levels nearing 200 ng/ml in their bloodstreams. A week later, blood levels were still between 20 and 35 ng/ml, on average.
In contrast, the highest concentration of avobenzone was 4.3 ng/ml, and it took much longer to reach that level. For octocrylene, maximum concentration was 7.8 ng/ml. And for the one sunscreen containing ecamsule, blood levels reached just 1.5 ng/ml with no residual concentration after a week.
Oxybenzone and Coral Reefs:
The state of Hawaii banned both oxybenzone and octinoxate last summer.
The legislation stated that these chemicals:
“have significant harmful impacts on Hawaii’s marine environment and residing ecosystems.”
“Studies have documented the negative impact of these chemicals on corals and other marine life. Our natural environment is fragile, and our own interaction with the earth can have lasting impacts. This new law is just one step toward protecting the health and resiliency of Hawaii’s coral reefs.”
What Should We Learn About Sunscreen Absorption?
The scientists conducting this study do not consider it the last word on sunscreen ingredient absorption. They present it as proof that such studies are feasible, however. The FDA may encourage manufacturers to carry out similar studies to demonstrate whether their sunscreen products are absorbed into the body. If they are, toxicity studies should be carried out. Do you not find it astonishing that this kind of research has not already been done?
Editorial in JAMA Interpreting the Results:
In the Same issue of JAMA there is an editorial by Robert Califf, MD, former FDA Commissioner and Kanade Shinkai, MD, PhD, Editor in Chief, JAMA Dermatology. These two heavy hitters note that there was evidence sunscreens were absorbed systemically over 20 years ago and that research reported:
“the presence of the common sunscreen ingredient oxybenzone in 97% of urine samples collected as part of the National Health and Nutrition Examination Survey.”
They go on to add:
“The demonstration of systemic absorption well above the FDA guideline does not mean these ingredients are unsafe. However, the study findings raise many important questions about sunscreen and the process by which the sunscreen industry, clinicians, specialty organizations, and regulatory agencies evaluate the benefits and risks of this topical OTC medication. First and foremost, it is essential to determine whether systemic absorption of sunscreen poses risks to human health.”
We find it astonishing that after all these years there are so many unanswered questions. These two authorities add:
“At a minimum, physicians should recommend use of sunscreen formulations containing GRASE [generally recognized as safe and effective] ingredients such as titanium dioxide and zinc oxide as part of a larger program of photoprotection that includes seeking shade, and wearing protective clothing, hats, and sunglasses, until meaningful answers to these questions are available.”
The authors of the research in JAMA note, the mineral ingredients titanium dioxide and zinc oxide are considered safe and effective. Manufacturers using other sunscreen ingredients (chemical filters such as avobenzone or oxybenzone) will be expected to produce absorption data. Learn more about zinc oxide at this link:
Share your thoughts about the latest research on sunscreen absorption in the comment section below.