The combined use of insect repellent and sunscreen reportedly reduces UV protection

Conducted by CNRS researchers¹, an unprecedented study on the combined use of sunscreen and an insect repellent that is among the best selling in France during summer concludes that UV² protection decreases after application of the mixture. With the spread of tiger mosquitoes in many countries, it has become increasingly common for people to combine these two products during outdoor activities³ to protect themselves from both the sun and these pests. This is the first paper that studies the effects of such a mixture. It has just appeared in Parasites and Vectors.

In order to reproduce the real conditions to which the human epidermis is subjected as faithfully as possible, scientists have used skin biopsies⁴. Optimally preserved ex vivo, these samples were subjected to artificial and natural UV rays emitted by the Sun, after application of sunscreen and repellent. Thanks to a new computer tool developed by one of the partner companies of this study⁵, they were analyzed in the form of thin slices corresponding to the different layers of the skin. This software, a deep-learning artificial intelligence system⁶, made it possible to measure the stress response of skin cells to the radiation.

The analysis of these data points to a decrease in UV protection in the case of a mixture of sunscreen and insect repellent. For "mixed" products, presenting themselves as carrying both protections at the same time, the data obtained are less categorical. Further studies are needed to consolidate and extend these initial results. Many other product mixtures, including cosmetics, have never been studied as such. This new analytical method, combining the use of biopsies (more reliable than tests on in vitro cultured cells) and artificial intelligence, would now allow the examination of their effects on human health.

Notes

1 – From the Institut des Sciences de l'Évolution de Montpellier (CNRS, IRD, Université de Montpellier).

2 – UV, which stand for Ultra Violet, are rays that are invisible to the naked eye. They carry more energy than visible light ; therefore, they can cause detrimental mutations to skin cells if one is exposed to them for too long.

3 – Tiger mosquitoes originate from South East Asia. They were accidentally transported to Europe during the 1990s and 2000s. Unlike their western cousins, they are livelier at daylight, hence why they tend to sting more during the day.

4 – Sample (a skin one here) collected from a living organism.

5 – This study was conducted in partnership with two French companies : QuantaCell and EDENCOS.

6 – Deep-learning is a methodology which is used to train artificial neuron networks. They are given a very large amount of data in order to learn about a phenomenon or to spot specific patterns that they are able to identify in future data sets.