Sunscreens can work their way into the bloodstream

Sunscreens are one of the most essential means to protect oneself from the harmful UV rays of the sun and protect oneself from skin cancer. Skin cancer, say health officials, remains one of the most common cancers diagnosed in the United States. Millions of people use sunscreens with an SPF of over 15 when stepping out. New studies are focussing on the safety of these sunscreens for long term use.

A recent trial called “MUsT” or maximal usage trial looked at the long term use and safety of sunscreens. The study was titled, “Effect of sunscreen application under maximal use conditions on plasma concentration of sunscreen active ingredients: a randomized clinical trial”. The study results were published yesterday (6th of May 2019) in the latest issue of the Journal of the American Medical Association. This pilot study was conducted by the Center for Drug Evaluation and Research, an arm of the US Food and Drug Administration.

Image Credit: Rawpixel / Shutterstock
Image Credit: Rawpixel / Shutterstock

The researchers looked at four commonly available sunscreen products that are used maximally in a population. They observed the amount of the drug absorbed via the skin when applied over it maximally as directed by the manufacturers. Results revealed that all of the four active ingredients present in the formulations of sunscreen were absorbed via the skin. The researchers add that there is no evidence that these ingredients are unsafe but say that more studies are necessary to evaluate the safety of these ingredients when they are absorbed via the skin.

They also state that most of the safety tests are part of a product’s approval and need to be conducted before it is available for use. Same is true for each of these ingredients, the authors of the study assure. The U.S. Food and Drug Administration (FDA) now strictly regulates sunscreens like other drugs and formulations and has the same stringent set of rules that go into their approval. As part of the new rule, the FDA has called upon manufacturers to come up with extensive safety data on 12 active ingredients present in commonly available sunscreen formulations. The FDA states that ingredients that are absorbed 0.5 ng/mL (nanograms per milliliter) or higher in blood need to undergo strict safety tests to see if they could lead to cancers or birth defects in the users. According to this latest study, these four ingredients in question have a higher than the 0.5 ng/mL absorption in blood. Their safety is not yet ascertained.

The study focuses on maximal use of these products as well as their use in young children and in pregnant women. The authors explain that as the sunscreens become more powerful and broad spectrum to protect against the UV rays of the sun, the concentrations of their key ingredients tend to rise.

First author Murali K. Matta and colleagues included 24 healthy participants who applied the 4 commercially available sunscreen formulations. The randomized clinical trial was conducted at a phase 1 clinical pharmacology unit. The four ingredients they studied included avobenzone, oxybenzone, octocrylene, and ecamsule. They were asked to apply 2mg of the sunscreen per 1 cm2 to 75% of body surface area 4 times per day for 4 days. The team collected 30 blood samples over 7 days from each of the participants. Maximum plasma concentrations of Avobenzone in the 2 sprays, lotions and creams respectively were 4.0 ng/ml, 3.4 ng/ml, 4.3 ng/ml and 1.8 ng/ml. For oxybenzone similarly the values were 209.6 ng/mL, 194.9 ng/mL, 169.3 ng/mL for spray 1, 2 and lotion respectively. For octocrylene absorption level was 2.9 ng/mL, 7.8 ng/mL, 5.7 ng/mL and 5.7 ng/mL for 2 sprays, lotion and cream respectively. For ecamsule the values were 1.5 ng/mL for the cream. Rash was the commonest side effect observed with the use of the sunscreens.

The authors conclude, “The systemic absorption of sunscreen ingredients supports the need for further studies to determine the clinical significance of these findings. These results do not indicate that individuals should refrain from the use of sunscreen.”

Dr. David Leffell, a spokesman for the American Academy of Dermatology and Yale School of Medicine dermatologist, in a statement said, “Studies need to be performed to evaluate this finding and determine whether there are true medical implications to absorption of certain ingredients.” Scott Faber, senior vice president for government affairs at the Environmental Working Group, or EWG, in his statement said, “The sun is the real enemy here... It's not news that things that you put on your skin are absorbed into the body. This study is the FDA's way of showing sunscreen manufacturers they need to do the studies to see if chemical absorption poses health risks.”

A decade old study from the US Centres for Disease Control and Prevention (CDC) had looked into the levels of oxybenzome in the urine samples of participants and found it in 97% of the samples. Oxybenzome present in the sunscreens is linked to hormonal changes in boys, shorter pregnancies and low birth weights of babies etc. Oxybenzone in sunscreens is also known to cause contact allergies. Hawaii has since then banned the use of oxybenzone and octinoxate in sunscreens because it could damage the marine ecosystem and bleach the corals. The European Union too has eliminated oxybenzone from sunscreen products. But oxybenzone remains in use in the US with at least two thirds of the sunscreens sold in nation containing the chemical.

Commeting on the latest study, former FDA Chairman Dr. Robert Califf assured that the results of the study do not “mean these ingredients are unsafe.” The Personal Care Products Council, the national trade council for sunscreen, cosmetic and personal care product chief scientist, Alex Kowcz said, “The presence of sunscreens in plasma after maximal use does not necessarily lead to safety issues. It's important for consumers to know that for the purpose of this study, sunscreens were applied to 75% of the body, four times per day for four days -- which is twice the amount that would be applied in what the scientific community considers real-world conditions.” She added that reports of this kind may dissuade the general population from using sunscreen.

The American Academy of Dermatology recommends application of at least 1 ounce of sunscreen on the exposed parts of the skin every two hours or after swimming.

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.

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