Sunscreens, Sunscreen Chemical and Systemic Absorption
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New study on sunscreen absorption into the blood
A new 2019 study has not only provided us all with a good reminder that things that we put on our skin have the potential to get absorbed into the blood but have also triggered the US Food and Drug Agency to demand further toxicology testing of sunscreen ingredient from manufacturers.
The study was a randomized study of 24 patients (12 men and 12 women) who applied sunscreens 4 times a day to 75 % of their body surface area for four days. 6 patients use a lotion, 6 used a cream, 6 used a spray and 6 used a second type of sunscreen spray. These sunscreens contained ingredients avobezone, oxybenzone, octocrylene, and ecamsule. The sunscreen was applied at the current recommend amount - namely 2 mg per cm2. The study researchers collected 30 blood samples from study subjects not only for the 4 days that the sunscreen was applied but also 3 additional days as well. The study was conducted indoors in a somewhat artificial setting without exposure to heat, sunlight, or moisture.
What were the main results of the study?
Matta and colleagues found that after 4 applications on day 1, 23 of 24 subjects had systemic concentrations greater than 0.5 ng/mL for all active ingredients in the formulation applied. This concentration is important because 0.5 ng/mL is the so called “Threshold of Toxicological Concern (TTC)” that the FDA adopted to approximate the highest plasma level below which the carcinogenic risk of any unknown compound would be less than 1 in 100,000 after a single dose. The average levels of avobenzone was 4.0 and 3.4 ng/mL in the 2 sunscreen sprays studied, 4.3 ng/mL in the lotion. Interestingly, the avobenzone concentration in the blood in those using the cream was lower at 1.8 ng/mL.
The numbers for the other sunscreen ingredients were also higher than the 0.5 ng/mL cut off. For oxybenzone, the corresponding values were 209.6 ng/mL for spray 1, 194.9 ng/mL for spray 2, and 169.3 ng/mL for lotion. The the ingredient octocrylene, the concentrations were 2.9 ng/mL for spray 1, 7.8 ng/mL for spray 2, 5.7 ng/mL for lotion, and 5.7 ng/mL for the cream cream. Finally for ecamsule, the systemic concentration was 1.5 ng/mL for the one product that contained it (cream).
The researched showed that the blood levels above this “0.5 ng/mL” level were reached quickly: within 6 hours after the first application of avobenzone, 2 hours after application of oxybenzone, and 6 hours after application of octocrylene. In addition, there was evidence that these drugs accumulated in the blood after more and more exposure.
I actively follow the sunscreen research field because it may (or may not) be related to at least some of the hair conditions I treat. The links to the hair loss are still not clear and so this makes it even more important to dive in an understand what these products do and don’t do in the body and to the body. What was really interesting to me about this study was that it was actually created because the FDA could not get sunscreen manufacturing companies to provide good toxicology data. Some have even suggested that the fact the the FDA did the testing indicates that the FDA has some amount of concern for the paucity of good data on safety. One should be aware that the FDA does not normally do testing - it is mainly a regulatory agency.
The authors of the present study did not conclude that we should not be using sunscreen - only that more safety type studies are needed. Sunscreen clearly reduce the risk of us developing certain types of skin cancers and reduce our risk of photoaging and burns.
There are many important questions that need to be considered when thinking about the role of sunscreens in hair loss medicine. First, sunscreen block ultraviolet radiation which is naturally immunosuppressive to the skin. When this in turn affects inflammation in the skin and hair in patients with inflammatory hair loss disorders is not known. In addition, we must keep in mind that animal studies have raised concerns that chemicals like oxybenzone might disrupt normal hormone patterns in humans. More study is needed to understand the effects in humans. It’s important to emphasize again and again that the precise link (or lack of a link) of sunscreens to hair loss issues (like frontal fibrosing alopecia) is still not known.
We’ll be hearing a whole lot more about safety and toxicology data of sunscreens as the FDA has given sunscreen manufacturers a deadline of November 2019 to provide them with safety data. This includes data on how they are absorbed, the risk of cancers, risks to reproductive health. This is a reminder to us that really solid human safety data on sunscreen use by humans is lacking. Hopefully the new data coming soon will clarify things.
Matta et al. Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients. A Randomized Clinical Trial. JAMA. 2019;321(21):2082-2091. doi:10.1001/jama.2019.5586
Moreno-Arrones OM et al. Factors influencing frontal fibrosing alopecia severity: a multicentre cross-sectional study.J Eur Acad Dermatol Venereol. 2019 Mar 21. doi: 10.1111/jdv.15590.
Califf RM, Shinkai K. Filling in the Evidence About Sunscreen. JAMA. 2019 May 6. doi: 10.1001/jama.2019.5528.
Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Whistler office at 604.283.1887