When perfume is applied to the skin, fragrance compounds enter the air and reach the nose. What chemical reactions take place around the skin along the way? In 2025, Nora Zannoni and colleagues investigated how perfumes and body lotions alter the oxidizing capacity generated close to the human body.
Central to the study is a highly reactive chemical species called the hydroxyl radical, or OH. The researchers measured air in an occupied experimental chamber and combined models of chemical reactions and airflow. They found that not only perfume’s fragrance compounds but also its solvent, ethanol, and ingredients in lotion strongly influence the amount of OH.
What is the oxidation field around the skin?
Ozone entering a room reacts with compounds such as squalene in skin oils. Some of the resulting substances are emitted into the air, where further reactions with ozone produce OH. The authors call this region around the body, where OH-driven oxidation reactions occur, the human oxidation field.
It is neither a visible membrane surrounding the body nor a measure of skin aging. It is a reaction environment in which chemicals in the surrounding air are transformed into other substances. Earlier research restricted personal care product use, so this study asked what happens when everyday perfumes and lotions enter that environment.
Comparing conditions with and without products in a room occupied by four people
The experiment used a 22.5-cubic-meter indoor chamber. Four men aged 19–27 sat in the chamber during each experiment, at about 26°C and 25% relative humidity, with 2.9 air changes per hour. The researchers examined conditions without ozone and with added ozone producing approximately 38–45 ppb in the occupied room.
Lotion and perfume were tested in separate participant groups. In the lotion experiments, a commercially available fragrance-free product was applied to the exposed skin of all four participants and compared with a baseline without application. In the perfume experiments, commercially available ck one was sprayed once on the back of each hand of two of the four occupants. Conditions included application 5–7 minutes before entering the chamber and application while inside.
Measurements covered airborne volatile organic compounds, ozone, and OH reactivity: how rapidly airborne substances consume OH. OH concentration itself was calculated from these measurements under the assumption that production and consumption were balanced. A chemical model also compared conditions with and without products, while a fluid-flow model estimated concentration distributions around the body.
In perfume, ethanol mattered more than fragrance compounds
Terpenes in perfume, such as limonene, can produce OH by reacting with ozone, but can also consume OH by reacting with it. Fragrance compounds alone therefore do not determine whether OH increases or decreases. What mattered in this study was ethanol, emitted in far greater quantities.
Immediately after perfume was applied inside the chamber, ethanol reached approximately 3,740 ppb and total monoterpenes approximately 10.6 ppb. Ethanol made the largest contribution to OH consumption at that point, with a calculated contribution of 76%. OH concentration estimated from the measurements fell by about 86% when perfume was applied. The explanation is that consumption, mainly by ethanol, outweighed OH production from fragrance compounds.
However, this large change occurred immediately after spraying. In the experiment with perfume applied before entry, the model indicated that many readily volatile compounds had already entered the air before the participants entered, making the subsequent effect on OH smaller. Even when perfume was sprayed indoors, ventilation removed compounds, and OH reactivity fell to about one-third within roughly 30 minutes. The same state of wearing perfume can therefore have different effects depending on elapsed time and where it was applied.
Lotion changes both production and consumption
Lotion ingredients such as phenoxyethanol entered the air and consumed OH. The pathways leading to OH formation also changed. A substance called 6-MHO, produced by oxidation of skin oils, is an important source of OH, but its steady-state chamber concentration was 34% lower with lotion than under baseline conditions.
The authors interpret this as lotion diluting skin-oil constituents and making reactions between ozone and skin oils less likely. The model represented this process by assuming that lotion mixes with skin oils. Lotion thus appears both to add OH-consuming compounds and to reduce the supply of substances from which OH forms.
In simulations combining perfume and lotion, perfume had the stronger effect immediately after application, while lotion became more important later. Ethanol quickly enters the air and is removed by ventilation, whereas phenoxyethanol in lotion is released relatively slowly. This time-dependent pattern for combined use was a modeling result.
Does less OH mean a health benefit?
The authors consider these changes important because OH transforms indoor chemicals, potentially affecting the kinds and quantities of substances we inhale or that contact our skin. A model incorporating airflow also showed product emissions traveling upward in the thermal plume generated by body heat and accumulating near the breathing zone. Room-average measurements may not adequately represent the air near the face.
The paper discusses how oxidation products can sometimes be more water-soluble than their parent compounds and transfer more readily into lung fluids. The authors therefore note that suppressing OH could reduce some harmful reaction products. Conversely, oxidation can sometimes reduce toxicity, and exposure to substances emitted by the products themselves must also be considered.
This experiment did not measure health symptoms, lung effects, or odor intensity, pleasantness, or unpleasantness. It examined one perfume and one lotion under limited indoor conditions with young men present. Although the authors anticipate broader relevance to products such as ethanol-based perfumes, they did not measure every product. Reduced OH alone does not establish either that perfumes or lotions should be used for health reasons or that using them is dangerous.
Summary
Perfumes and lotions do more than simply evaporate from the skin. They join reactions beginning with skin oils and ozone, changing both the rate at which OH is produced and the rate at which it is consumed. In the perfume tested here, ethanol immediately after spraying explained the effect; for lotion, interactions with skin oils and slowly released ingredients were important.
The study shows that understanding air around people requires considering solvents, products remaining on the skin, elapsed time since use, and ventilation, not just the names of fragrance compounds. The next challenge is to establish which substances these changes actually produce in the breathing zone and what effects each has.
References
Zannoni, N., Lakey, P. S. J., Won, Y., Shiraiwa, M., Rim, D., Weschler, C. J., Wang, N., Arnoldi-Meadows, T., Ernle, L., Tsokankunku, A., Bekö, G., Wargocki, P., & Williams, J. (2025). Personal care products disrupt the human oxidation field. Science Advances, 11(21), eads7908. DOI: 10.1126/sciadv.ads7908 / Full original article.
Original article: © 2025 The Authors. Exclusive licensee: American Association for the Advancement of Science. CC BY 4.0.
