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Sunscreen’s Active Ingredients Effect on the Body and Blood Plasma Concentrations

Kimberly England's picture
Sunscreen on a human leg

As we move into the summer months, many consumers will want to reduce the risk of sun exposure by using a topical sunscreen. But apparently, sunscreens have serious risks.

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We are often prompted with advertisements and medical suggestions to avoid the risk of UV rays and possible skin cancer by using sunscreen. However, new studies seem to suggest that sunscreen may be causing more harm than good. So, what do we really know about the risk of sunscreen and how it affects us?

In a small new pilot study, JAMA published online research findings of clinical significance on May 6, 2019 that demonstrated some ingredients of sunscreens which are absorbed into the body and bloodstream. Although the study used 24 healthy volunteers and concluded the systemic absorption of sunscreen ingredients prompting a need for further studies, it did not show a study on unhealthy volunteers. The preliminary study involved 4 commercially available sunscreens under maximal use conditions which resulted in plasma concentrations that exceeded the threshold established by the FDA. It did conclude and reveal the systemic absorption of sunscreen ingredients supports the need for further studies.

Objective
To determine whether the active ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule) of 4 commercially available sunscreens, are absorbed into systemic circulation.

Design, Setting, and Participants
A randomized clinical trial conducted at phase 1 clinical pharmacology unit in the United States and enrolling 24 healthy volunteers. Enrollment started in July 2018 and ended in August 2018.

Intervention

Participants were randomized to 1 of 4 sunscreens: spray 1 (n=6 participants), spray 2 (n=6), a lotion (n=6), and a cream (n=6). Two milligrams of sunscreen per 1 cm2 was applied to 75% of body surface area 4 times per day for 4 days, and 30 blood samples were collected over 7 days from each participant. The primary outcome was the maximum plasma concentration of avobenzone. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, and ecamsule.

Results

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Among 24 participants randomized (mean age, 35.5 [SD, 1.5] years; 12 (50%] women; 14 [58%] black or African American; 14 [58%]), 23 (96%) completed the trial. For avobenzone, geometric mean maximum plasma concentrations were 4.0 ng/mL (coefficient of variation, 6.9%) for spray 1; 3.4 ng/mL coefficient of variation 77.3%) for spray 2; 4.3 ng/mL (coefficient of variation, 46.1%) for lotion, and 1.8 ng/mL (coefficient of variation, 32.1%). For oxybenzone, the corresponding values were 209.6 ng/mL (66.8%) for spray 1, 194.9 ng/mL (52.4%) for spray 2 and 169.3 ng/mL (44.5%) for lotion; for octocrylene, 2.9 ng/mL (102%) for spray 1, 7.8 ng/mL (113%) for spray 2, 5.7 ng/mL (66.3%) for lotion and 5.7 ng/mL (47.1%) for cream; and for ecamsule 1.5 ng/mL (166.1%) for cream. Systemic concentrations greater than 0.5 ng/mL were reached for all 4 products after 4 applications on day 1. The most common adverse event was rash, which developed in 1 participant with each sunscreen.

Conclusion and Relevance

The Conclusions and Relevance in this preliminary study, involved healthy volunteers, an application of 4 commercially available sunscreens under maximal use conditions. It resulted in plasma concentrations that exceeded the threshold established by the FDA for potentially waiving some nonclinical toxicology studies for sunscreens. The systemic absorption of sunscreen ingredients supports the need for further studies to determine the clinical significance of these findings. The results do not indicate that individuals should refrain from the use of sunscreen but question the effects of toxic ingredients on the body and plasma. More information on the Abstract of study can be found here.

doctors studying sunscreen

Blood levels of all four compounds exceeded the level above which the US Food and Drug Administration, FDA, recommendations that companies should test for toxic effects. In almost all volunteers, all the tested compounds reached blood levels higher than the required threshold level of 0.5 ng/ml and sometimes much higher with a single day sunscreen use. The FDA has tried and failed to get sunscreen manufacturers to conduct toxicity testing according to an expert reaction. “The authors suggest their findings mean we should do further testing to determine the clinical significance of these findings. There is no evidence from this study that there is any health risk. And at maximal use, any theoretical risk is almost certainly far smaller than the reduced risk of skin cancer that has been shown to be associated with sunscreen use. Indeed, the authors themselves say that their results do not suggest that people should refrain from using sunscreen. “Furthermore, each participant in the study applied the equivalent of two standard bottles of sunscreen over four days. This is considerably greater than typical use as people who use sunscreen go through only about one bottle per year per person.”

Prof Dorothy Bennett, Director of the Molecular and Clinical Sciences Research Institute, St. George’s, University of London, said: "Please note: my expertise is in skin cancer and UV light rather than toxicology. However I can understand the article and the analysis. The editorial appears to comment in a fair way on the limitations of the study. The press notice seems a reasonable summary and the science looks reliable."

Assessment of the Human Systemic Absorption of Sunscreen Ingredients by U.S. National Library of Medicine, Clinical Trial Identifier: NCT03582215.

Natural Sunscreens
Fortunately, there are sunscreens that exclude the above-mentioned active ingredients. Consumers may find alternative sunscreens that use titanium dioxide and zinc oxide minerals required by the FDA in commercial sales. These ingredients tend to provide a physical barrier rather than a chemical barrier between the UV rays and your skin. The problem is these two products in this category have consistently performed less effectively in testing than their chemical cousins. If you want a sunscreen without chemicals, consider California Kids #Supersensitive Lotion SPF 30+. It was the highest-performing “natural” sunscreen. It has an overall Good rating, a Very Good score for UVB protection. This is rated only Fair for UVA protection according to Consumer Reports.

Follow Kimberly England on Twitter at @MrCarrotTopG2W and Instagram at Author Kimberly England and send her tips for upcoming health news stories.

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