Researchers Uncover Hidden Risk in Popular Summer Skincare Combo

Mixing sunscreen with insect repellent may lower UV protection, according to a CNRS study using AI and skin biopsies.

Researchers from the CNRS have conducted a groundbreaking study on the combined use of sunscreen and one of France’s top-selling insect repellents. Their findings reveal that mixing the two products leads to a reduction in UV protection after application.

As tiger mosquitoes continue to spread across many countries, it’s become increasingly common for people to apply both products together during outdoor activities to guard against sun exposure and insect bites. This is the first scientific study to examine the effects of this combination. The research was recently published in the journal Parasites & Vectors.

Realistic Skin Testing and Advanced Imaging

In order to reproduce the real conditions to which the human epidermis is subjected as faithfully as possible, scientists have used skin biopsies. 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 study, they were analyzed in the form of thin slices corresponding to the different layers of the skin. This software, a deep-learning artificial intelligence system, made it possible to measure the stress response of skin cells to the radiation.

Findings and Future Research

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.

Reference: “Computational histology reveals that concomitant application of insect repellent with sunscreen impairs UV protection in an ex vivo human skin model” by Sophie Charrasse, Titouan Poquillon, Charlotte Saint-Omer, Audrey Schunemann, Mylène Weill, Victor Racine and Abdel Aouacheria, 4 March 2025, Parasites & Vectors.
DOI: 10.1186/s13071-025-06712-3

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