In a groundbreaking study published in Science Advances, researchers have unveiled how personal care products like lotions and fragrances profoundly alter the delicate chemistry of the air immediately surrounding the human body. This invisible but critical chemical environment, known as the "human oxidation field," plays a vital role in shielding humans from harmful pollutants such as ozone. The international team, including experts from Penn State University, demonstrates that these everyday products disrupt this protective chemical shield in ways previously unknown, raising important questions about indoor air quality and human health.
At the heart of this discovery lies the intricate interplay between human skin oils and ozone, a common air pollutant that seeps indoors from outdoor environments. Under normal conditions, our skin chemistry reacts with ozone molecules present in indoor air to produce hydroxyl radicals (OH radicals). These radicals are highly reactive molecules that generate a natural "chemical field" around a person, effectively serving as a defensive barrier by reducing the amount of ozone that penetrates directly into the respiratory system. Donghyun Rim, associate professor of architectural engineering at Penn State and co-author of the study, explains that this process is akin to an invisible shield, a continuous reaction zone moderated by the body's own temperature and biochemical emissions.
Human bodies, typically warmer than the surrounding environment, induce air movement towards the skin surface, facilitating these chemical reactions. This zone of interaction -- the human oxidation field -- is a dynamic, three-dimensional space where air quality is locally modified by the wearer's own skin chemistry. However, the research reveals that personal care products, despite their commonplace use, introduce complex organic compounds that significantly alter this protective chemical mechanism. Fragrances and lotions change both the concentration and reactivity of hydroxyl radicals, effectively destabilizing the shield that helps mitigate ozone exposure.
During carefully controlled experiments, volunteers were placed inside a chamber infused with ozone to simulate real-world indoor environments. Initial measurements captured a baseline of hydroxyl radical production and human oxidation field characteristics without any external substances applied to the skin. Following this, participants applied either unscented lotions or scented fragrances, allowing the researchers to observe how these widely used personal care products reshape the chemical landscape of the air closely surrounding the body.
What emerged was a striking pattern: unscented lotions caused a profound increase -- approximately 170% -- in OH radical reactivity but paradoxically led to a roughly 140% reduction in hydroxyl radical concentration around the wearer. This means that although the chemical reactions accelerated, the effective concentration of protective radicals that form the ozone barrier diminished significantly. The study demonstrates that these radicals were being carried away from the skin into the surrounding air, weakening the immediate defense against ozone exposure.
In contrast, fragrances exhibited a different temporal dynamic. The volatile organic compounds present in scented products, such as ethanol, rapidly emitted into the air and initially caused stronger disruptions in hydroxyl radical chemistry. However, their effects were less persistent over prolonged periods compared to lotions. Such differentiation highlights that not all personal care products influence indoor air chemistry equally, and their impact fluctuates over time depending on their chemical makeup and volatility.
The implications of these findings extend beyond mere curiosity about personal fragrance preferences. Since research shows that people spend up to 90% of their time indoors, often in environments where outdoor ozone infiltrates continuously, understanding how everyday personal care routines modify the human oxidation field is critical. These modifications potentially influence actual inhaled pollutant doses and may lead to previously unrecognized health outcomes related to indoor air pollution.
To complement experimental findings, the team developed a sophisticated three-dimensional computational fluid dynamics model capable of simulating the evolution of the human oxidation field in indoor environments. This model incorporated human physiology, skin chemistry, air flow dynamics, and the influence of organic compounds emitted from personal care products. By doing so, it provided unprecedented insight into how chemical reactions unfold in the breathable microenvironment directly surrounding the human body, reaffirming the observed experimental trends and projecting their consequences in real-world indoor settings.
Although the study pioneers understanding in this niche field, the researchers emphasize that many questions remain about the secondary chemical byproducts generated throughout these complex skin-ozone interactions. Some reaction products could have unknown toxicity or could contribute to indoor secondary pollution, affecting air quality and respiratory health. The intricate balance between beneficial ozone absorption by skin and the unintended emission of reactive gases demands further inquiry.
This multifaceted project also showcases the power of interdisciplinary collaboration, bringing together atmospheric chemists, engineers, and environmental health scientists from institutions across the globe. Penn State researchers Rim and Youngbo Won contributed with cutting-edge experimental and modeling expertise, supported by colleagues at the Max Planck Institute for Chemistry, the University of California Irvine, and the Technical University of Denmark. This international effort broadens the scope of indoor air quality research, potentially informing better guidelines for personal care product formulations and indoor environmental standards.
Funded in part by the Alfred P. Sloan Foundation, the work bridges engineering, chemistry, and health sciences, representing a leap forward in understanding how chemical microenvironments around the human body affect overall exposure to pollutants. These novel insights may catalyze the development of new personal care products designed to minimize disruption of the human oxidation field or advanced indoor ventilation strategies that consider occupant-emitted chemistry.
As this emergent area of research gains traction, the hope is to empower consumers with knowledge about how their personal care habits unintentionally influence indoor air quality and health. The invisible chemistry shaped by lotions and perfumes might hold the key to mitigating ozone-related health risks in everyday settings, redefining the relationship between personal grooming and environmental exposure.
Subject of Research: People
Article Title: Personal care products disrupt the human oxidation field
News Publication Date: 21-May-2025
Web References: https://www.science.org/doi/epdf/10.1126/sciadv.ads7908
References: Rim, D., Zannoni, N., Won, Y., Williams, J., Wang, N., Arnoldi-Meadows, T., Ernle, L., Tsokankunku, A., Lakey, P.S.J., Shiraiwa, M., Weschler, C.J., Bekö, G., Wargocki, P. (2025). Personal care products disrupt the human oxidation field. Science Advances. DOI: 10.1126/sciadv.ads7908
Image Credits: Jeff Xu/Penn State
Air pollution, Indoor air quality, Ozone, Hydroxyl radicals, Human oxidation field, Personal care products, Fragrance chemistry, Indoor environmental health, Computational fluid dynamics, Skin chemistry, Reactive oxygen species, Pollutant exposure