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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
Hair products used in hair salons release aerosols that can cause respiratory tract irritation if inhaled. Under a contract from industry, researchers at the Fraunhofer Institute for Toxicology and Experimental Medicine ITEM investigated the effects of aerosols produced when using heated chemical hair products. Using an innovative cell-based in vitro inhalation method, the researchers can estimate effects on the respiratory tract and identify potentially harmful substances. This non-animal testing method supports safe product development that is fully in line with the safe-by-design approach, which integrates safety in product development right from the start.
Hairstylists are exposed to inhalable substances such as chemical fumes or ultrafine particles in the air. In some cases, inhalation of the aerosols released when using heated hair products may lead to respiratory discomfort. But there were previously no in vitro methods for verifying the health effects of these aerosols on the respiratory tract. What is the role of product composition? Does the nature of the application have an effect on possible health risks? What are the effects of the quantity of aerosols released? These questions could not be investigated or clarified using any of the previously available methods. EU regulations only permit the use of methods that do not involve animal experimentation for toxicological testing of cosmetics. Alternative methods are therefore needed. Researchers at Fraunhofer ITEM in Hannover have developed just such a method: a cell-based in vitro inhalation approach that helps industry develop products that are safe by design and meet regulatory requirements.
Optimizing products before placement on the market
Working under the industrial contract, the experts used the in vitro inhalation method to clarify the respiratory effects of heated hair treatment products. The liquid chemical is applied to the strands of hair and is then smoothed over the hair with an iron heated to approx. 200 degrees Celsius. This process releases aerosols that could potentially affect a hairstylist’s respiratory tract. While some products indicated an elevated potential for such effects, it was not previously possible to establish any clear relationship between the product and the application method. The study aimed to use the new approach to better understand respiratory effects without animal testing, realistically assess the inhalation risk posed by aerosols and test existing products before market launch, improving them where necessary.
Fraunhofer ITEM research scientist Detlef Ritter says: “The in vitro inhalation method can be used to investigate everything that can be inhaled, regardless of the source. The substances tested can be exhaust gases, nanoparticles, PFAS or, as in this case, aerosols from cosmetic sprays or hairstyling products. For example, in a previous project, we were already able to modify the formulation of a room spray for a client to render it harmless for human health. We managed to identify and replace an unsuitable component in the spray product.”
Using human lung cells to realistically evaluate the inhalation risk of aerosols
Ritter and his team investigated four different test materials in their study of chemical hair products. The aerosols were generated by applying the products to strands of real hair and were tested and analyzed under optimized conditions by exposing human lung cells to them in the patented P.R.I.T.® ExpoCube® system. The exposure unit developed at Fraunhofer ITEM enables in vitro testing of volatile chemicals or aerosols that cannot be investigated using traditional submersive cell culture methods in which the cells are covered by culture medium. The lung cells are cultivated at the air-medium interface, precisely as in the human respiratory tract. A sophisticated system using micropumps, electronic heaters, aerosol lines and sensors is used in the ExpoCube® to enable controlled and reproducible exposure of the cell cultures to the various aerosols at the air-liquid interface, just as in the actual human lung.
In vitro results correlate with hairstylists’ experiences
Dose-response tests were used to investigate cell viability, mitochondrial function, cellular stress and the release of interleukin-8 as a representative marker for the body's inflammatory response. Some of the four test materials had caused nonspecific symptoms, such as mild discomfort or a scratchy throat, when used by hairstylists. Conversely, other products never caused any discomfort. “Characterization of the aerosols released when the four hair products were applied to strands of real hair under realistic conditions revealed significant differences in aerosol formation rates and dose response. Cell viability and mitochondrial function remained unaffected, but there were significant differences in cellular stress and IL-8 release,” Ritter summarizes. “What is critical is that the product characteristics determined in our test results correlated exactly with the feedback provided by the hairstylists. The in vitro results aligned with the observations in real-world conditions.” Furthermore, the research team was able to demonstrate that although the extent of aerosol release also depends on the method used to treat the strands of hair (more intense at higher temperatures and with many passes; more moderate at lower temperatures and with few passes), the test material used was the determining factor and significantly influenced the biological effect. “The degree of aerosol release and the respiratory effect is especially determined by the specific properties of the product, such as the composition of its ingredients,” says the researcher.
The results were obtained with a very compact in vitro model, opening up the possibility of routine use, integration in product development strategies and further use in toxicological research. This approach contributes substantially to the refinement and acceptance of alternative methods within safe-by-design concepts and safety assessment strategies.
https://www.fraunhofer.de/en/press/research-news/2026/august-2026/non-animal-tes...
The liquid chemical is applied to the strands of hair and is then smoothed over the hair with an iro ...
Copyright: © Fraunhofer ITEM/Ralf Mohr
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The liquid chemical is applied to the strands of hair and is then smoothed over the hair with an iro ...
Copyright: © Fraunhofer ITEM/Ralf Mohr
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