A study by CNRS researchers highlights a drop in effectiveness of UV protection during the combined use of sunscreen and anti-mosquito repellents. Abdel AouacheriaResearch manager at the CNRS who directed this work, details them for Medscape.
Explore the consequences of a multiple exhibition
“Our study starts from a simple observation: more and more frequently, on the beaches of Occitania, people with outdoor activities tend to spread not only sunscreen, but also anti-mosquito in order to fight against insects that even bite during the day,” Abdel AouacheriaCNRS research manager at the Montpellier Institute of Evolution Sciences. “This observation raises the question of the consequences of a multiple exhibition. However, when manufacturers test the safety of their products, they do not do so in combination with other substances. Only research laboratories can do so, ”he notes. Another problem: the plethoric offer of products available on the market makes their analysis difficult. The research team therefore had to start by identifying the most commonly used products.
“We conducted an investigation around Montpellier, by visiting pharmacies and supermarkets and by studying products on the shelves and sales. This allowed us to take a panorama of the best -selling products in Occitania, ”explains the researcher. “We thus set our sights on a very used anti-mosquito, Tropic five out of five, and on a Nivea sunscreen. We added a product combining repellant and solar, ”he said.
By adding anti-mosquito repellants, the degree of protection offered by sunscreen has halved
Quantify the degree of damage to cells
Then, scientists used skin biopsies that they subjected to artificial, but also natural UV rays, emitted by the sun, after applying sunscreen and repellents. “This makes it possible to reproduce the human epidermis as faithfully as possible,” said Abdel Aouacheria.
The skin samples were then cut into very thin slices and observed under microscope. “We have collected images that we have made analyzed by an artificial intelligence driven by deep learning, capable of locating where the epidermis is located and quantifying the degree of damage to skin cells at this place,” he said. The criterion chosen was the number of haloed nuclei which condenses in damaged cells and are therefore markers of apoptosis, that is to say the death of cells.
“When you put sunscreen, we protect the skin from the effects of stress related to UV irradiation, in the laboratory or solar. On the other hand, the surprise came when we added anti-mosquito repellents. The degree of protection offered by sunscreen has halved, ”says the researcher. Regarding the “mixed” product, the results were more mixed.
Start by putting the sunscreen, then the repellent, and if possible 20 minutes between the two applications
Questions about the combined use of products
For Abdel Aouacheria, “this study questions the combined use of products. We could test other solar products, other repellents, but also mix with makeup products or creams. It is a vast subject that opens, for which we have no data, ”he believes. He hopes that other laboratories “grab this question to do tests on wider panels of individuals, with different degrees of pigmentation”. In the meantime, he advises consumers to “stick to the recommendations that exist: start by putting the sunscreen, then the repellent, and leave 20 minutes between the two applications if possible. You must also ensure the application frequencies. For sunscreen, you have to put it every two hours and after swimming. As for the anti-mosquito side, it’s every six hours, “he recalls.
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