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Experts React to Sunscreen Blood Absorption Warning: Keep Using Sunblock

Newsweek logo Newsweek 5/7/2019 Kashmira Gander

© nito100/Getty Images Scientists have urged the public to continue using sunscreen to protect against skin cancer, after a study showed the body can absorb ingredients found in common sunblock products. 

The study involved 24 healthy people who applied four common types of sunscreen on their skin. Researchers randomly assigned the participants one of four sunscreens: either one of two sprays, a lotion, or a cream. They put the cream on 75 percent of their bodies, four times a day, for four days. Over the course of 7 days, including the days sunscreen was used, the scientists collected 30 blood samples from the participants. The team looked at four ingredients: avobenzone,  oxybenzone, octocrylene, and ecamsule.

The research published in the journal JAMA was a randomized clinical trial, as well as what is known as a maximal usage trial. This is where researchers assess whether the active ingredients in a product applied to the skin are absorbed into the body when it is used at its maximum recommended level.

At the end of the study, the team found concentrations of the active ingredients in participants’ blood. These exceeded the levels set by the Food and Drug Administration which determine whether a product needs safety testing.

Past studies have found oxybenzone and octocrylene have been found in human breast milk, the authors wrote. Oxybenzone has also been identified in urine, blood and amniotic fluid. But scientists aren’t sure what this means for the health of sunblock users. More research is now needed to determine whether these levels are harmful, the authors said. 

The study was limited, the authors acknowledged, because the study was carried out in a lab where participants were exposed to sunlight, heat or humidity, which might affect how the product is absorbed. The next phase of the study will look at factors including how much of the ingredients are soaked into the body when a person applies sunscreen just once, and whether chemicals linger in the body 17 days after using such products.

The findings should not put people off using sunblock, the authors wrote: “these results do not indicate that individuals should refrain from the use of sunscreen.”

In a statement, the Food and Drug Administration said: “The fact that an ingredient is absorbed through the skin and into the body does not mean the ingredient is unsafe.

“Rather, this finding calls for further testing to determine the safety of that ingredient for repeated use. Such testing is part of the standard pre-market safety evaluation of most chronically administered drugs with appreciable systemic absorption.”

Professor Brian Diffey, emeritus professor of photobiology, dermatological sciences at Newcastle University commented: “It is important to note that each participant in the study applied the equivalent of two standard bottles of sunscreen over four days. This is considerably greater than typical use where it has been estimated that people who use sunscreen go through about one bottle per year per person.

"It is important to note there is no evidence from this study that there is any health risk. And even 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."

Dr. Andrew Birnie of the British Association of Dermatologists, who was not involved in the study, commented: "Sunscreen has been used by a large portion of the population for a number of decades and there has not been any epidemiological data that suggests users come to harm. We agree with the researchers that people should not make the knee-jerk decision to stop using sunscreen."

Birine said it is indisputable that sun exposure causes skin cancer, while the research into the potential harms of sunblock is at an early stage.

“The first line of defense against the sun should be shade and clothing, with sunscreen used for additional protection," said Birine.

According to the American Academy of Dermatology (AAD), skin cancer is the most common form of the disease in the U.S., with one in five Americans at risk of developing it in their lifetimes. Each day, around 9,500 are diagnosed with the disease.

The AAD says people should limit sun exposure and not use tanning beds in order to avoid harmful UV rays. Wearing protective clothing, and broad-spectrum, water-resistant sunblock with an SPF of at least 30 is also advised. 

Video: 5 Ways To Reduce The Risk Of Skin Cancer

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