UNIVERSITY PARK, Pa. — Everyday personal care products like perfumes and even unscented lotions may interfere with the body’s natural defense against air pollution, according to a new study led by an international team including Penn State researchers.
Published in Science Advances, the study found that these products disrupt the “human oxidation field”—an invisible chemical shield created by reactions between skin oils and indoor ozone. This shield, rich in hydroxyl (OH) radicals, plays a crucial role in reducing harmful ozone exposure near the skin and breathing zone.
“Think of it like a protective bubble formed around your body,” said Donghyun Rim, associate professor of architectural engineering at Penn State. “Our skin reacts with ozone, which helps prevent us from inhaling it directly.”
However, Rim noted that this process also produces secondary chemicals, whose health effects are not fully understood.
To investigate, researchers had volunteers sit in a chamber with ozone present, first without using any personal care products, then after applying either an unscented lotion or a common fragrance. The team used advanced 3D modeling to simulate and measure the resulting changes in the oxidation field.
They found that unscented lotion increased OH reactivity by 170%, leading to a 140% drop in OH concentration near the skin—meaning the natural ozone barrier was significantly weakened. Fragrances had a more immediate but shorter-lasting effect, dispersing quickly into the air.
“Lotions tend to linger and continuously emit compounds, making their impact on the oxidation field more persistent,” said study lead author Nora Zannoni of the Institute of Atmospheric Sciences and Climate in Bologna.
This research is especially relevant given that people spend up to 90% of their time indoors, where air quality is heavily influenced by chemical interactions with the human body.
The Penn State portion of the study was funded by the Alfred P. Sloan Foundation. Other co-authors include scientists from the Max Planck Institute for Chemistry, University of California, Irvine, and the Technical University of Denmark.
The findings highlight a new dimension of indoor air chemistry and raise questions about the long-term health effects of common personal care products.
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