In a breakthrough study published on May 21, 2025, in Science Advances, a team of international researchers from the University of California, Irvine, Germany’s Max Planck Institute for Chemistry, Pennsylvania State University, and other collaborators revealed compelling evidence that commonly used personal care products such as fragrances and body lotions can significantly alter a previously underexplored chemical phenomenon surrounding the human body known as the "human oxidation field." This discovery sheds new light on the complex interactions between human skin chemistry and indoor air quality, with implications spanning health, environmental science, and indoor living spaces.
The human oxidation field is a thin but chemically dynamic zone enveloping the body, arising from reactions between skin oils and indoor ozone molecules. Earlier research by the same interdisciplinary team, published in Science in 2022, identified the skin’s natural oils—most notably squalene—as critical reactants that engage with ambient ozone to produce highly reactive chemical species, including hydroxyl radicals. These radicals, known for their potent oxidative properties, catalyze cascades of chemical reactions that transform indoor air pollutants right in the immediate vicinity of a person’s breathing zone.
This newly-characterized microenvironment is influenced by numerous factors, among them emissions from everyday indoor sources such as cooking residues, cleaning agents, cigarettes, paints, upholstery fabrics, and furniture materials. Additionally, outdoor ozone infiltration further supplies necessary reactants. These reactive zones foster complex chemistry which until now was largely overlooked in assessments of indoor air quality and human exposure to airborne contaminants.
In the recent Science Advances publication, the researchers delve into how the application of personal care products alters this oxidation chemistry. Using a combination of advanced multiphase chemical kinetic modeling and computational fluid dynamics simulations, the team demonstrated that body lotions create a physical barrier on the skin surface. This barrier inhibits the reaction between ozone molecules and squalene, effectively suppressing the precursor formation of hydroxyl radicals. Consequently, the intensity of the human oxidation field is significantly diminished.
Moreover, the study found that ethanol, a common solvent in many fragrances, functions as a chemical sink for hydroxyl radicals. By reacting with and neutralizing these reactive species, ethanol reduces the overall concentration of hydroxyl radicals near the skin, further weakening the oxidation field. This dual mechanism reveals not only a physical but also a chemical mode by which personal care products modulate immediate human-environment chemistry.
Manabu Shiraiwa, UC Irvine professor of chemistry and co-corresponding author, spearheaded the development of the comprehensive chemical kinetic model, capturing multiphase interactions between skin secretions, airborne oxidants, and reactive intermediates. Collaborators at Penn State contributed fluid dynamic modeling to spatially resolve concentration gradients of reactive chemical species around the human form indoors. Together, these tools enabled unprecedented visualization and quantification of the human oxidation field’s behavior in realistic indoor settings.
According to Shiraiwa, “Our approach uniquely integrates skin surface chemistry with indoor atmospheric conditions to simulate the nuanced formation and transformation of reactive chemical species near humans.” This holistic modeling, combining chemical kinetics and fluid dynamics, advances understanding of how subtle chemical processes at the skin interface propagate into broader indoor air chemistry.
The implications of this research are far-reaching. Many indoor environments are tested for emissions from consumer products and furnishings to regulate exposure to harmful compounds before they reach occupants. However, these tests rarely consider the reactive transformations initiated by the human oxidation field upon contact with such emissions. The study points out that when a person interacts physically with furniture or objects, their skin chemistry can catalyze the generation of numerous secondary compounds whose health effects and chemical properties remain poorly understood.
Jonathan Williams, lead author and head of organic reactive species research at the Max Planck Institute, highlighted how this oxidation field modifies indoor air composition: “Even after emission testing, once a person is sitting on a sofa, the oxidation field generated by their skin actively transforms many of those materials, creating new compounds in their breathing zone. Notably, both body lotions and perfumes appear to attenuate this effect significantly.”
This insight compellingly suggests that everyday consumer products—beyond their cosmetic or olfactory roles—can modulate indoor chemical environments and human exposure risks. By mitigating the formation of reactive species, such products could potentially influence human health outcomes related to air quality, respiratory stress, and chemical sensitivities.
The research was conducted under the Indoor Chemical Human Emissions and Reactivity (ICHER) project, an international collaborative endeavor encompassing institutions across Denmark, Germany, and the United States. Computational modeling efforts were coordinated by the Modelling Consortium for Chemistry of Indoor Environments (MOCCIE) at UC Irvine, led by Shiraiwa. Funding was secured through grants from the Alfred P. Sloan Foundation, underscoring the strategic importance of deciphering indoor air chemical processes.
As indoor living continues to dominate human activity patterns globally, this work delivers critical new perspectives on how human-derived chemistry interacts dynamically with the built environment and the products within it. It establishes a foundation for future exploration into mitigating exposure to potentially harmful oxidation products and improving indoor air quality through informed use and design of personal care and furnishing materials.
Given the ubiquity of fragrances and lotions in modern life, the findings also open avenues for innovative product formulations aiming to harmonize personal care with environmental health. This intersection of chemistry, human biology, and indoor air science presents a frontier ripe for further interdisciplinary research and public health advancements.
Collectively, these findings redefine our understanding of the immediate chemical landscape surrounding the human body indoors. They invite a paradigm shift from viewing emissions and pollutants as static entities to recognizing the human occupant as an active chemical participant capable of modulating their personal air microenvironment in complex and consequential ways.
Subject of Research:
The influence of personal care products on the chemical dynamics of the human oxidation field and its impact on indoor air quality.
Article Title:
Personal care products disrupt the human oxidation field
News Publication Date:
21-May-2025
Web References:
https://www.science.org/doi/10.1126/sciadv.ads7908
https://www.chem.uci.edu/~mshiraiw/MOCCIE.html
References:
- Published article in Science Advances, May 21, 2025
- Previous related study in Science, 2022
Image Credits:
Not provided.
Keywords
Chemical compounds, indoor air chemistry, human oxidation field, hydroxyl radicals, skin-ozone interaction, personal care products, body lotion, fragrances, indoor pollutants, computational fluid dynamics, multiphase chemical kinetics, indoor environments
