A non-invasive technology for assessing the allergenic potential of chemical compounds found in cosmetics

Elena Giménez-Arnau specializes in the study of the chemical and molecular mechanisms underlying skin sensitization and contact allergy induced by substances foreign to the body (known as xenobiotics). As a member of the “Optical and Magnetic Properties of Molecular Architectures” (POMAM) laboratory in Strasbourg, she works at the intersection of chemistry and biology. 

“These skin reactions are very specific allergies for which there is no treatment other than avoiding the allergenic substances. Unlike food or respiratory allergies, different components of the immune system are involved, and desensitization is not possible,” explains the researcher, emphasizing the importance of regulating the molecules used in cosmetics. “The immunotoxicity process characteristic of allergic contact dermatitis begins when the allergenic molecule interacts with skin proteins to form an antigenic entity (that is, a molecular complex recognized as foreign by our immune system). This entity then activates the immune system, which triggers a defensive reaction upon subsequent contact with the allergen. In the case of certain allergenic molecules, this reaction with skin proteins occurs through the formation of free radicals—unstable molecules that are highly reactive and can react with skin proteins, thereby inducing sensitization.”

For many years, Dr. Giménez-Arnau has been studying the free-radical mechanisms that trigger skin dermatitis, in close collaboration with Dr. Bertrand Vileno, also a researcher at PONAM. Recently, she has focused specifically on photoallergic and photoirritant reactions triggered by sun exposure. “Certain cosmetics, perfumes, and even over-the-counter medications can trigger severe inflammatory skin reactions when exposed to the sun. This is the case with ketoprofen, a nonsteroidal anti-inflammatory drug used in creams for muscle and joint pain, as well as with certain sunscreens used in cosmetic products,” the researcher warns, noting that some products labeled “natural” may seem safer but can still contain allergenic compounds when exposed to the sun.

Elena Giménez-Arnau points out that it is not always the same types of free radicals that trigger skin reactions: “Oxygen-derived radicals (known as ROS) are already known to play a role in skin aging and have been identified as the cause of photoirritant dermatitis (an immediate reaction resulting in redness, a burning sensation, and itching). Carbon-centered radicals, on the other hand, may be responsible for photoallergic dermatitis (a delayed reaction that can lead to eczema, blisters, or patches).” These are two types of reactions that manufacturers must be able to identify when testing their products, and Elena Giménez-Arnau’s laboratory has focused on them to develop new tests that are essential for consumer safety.