Personal care products protect users from their own oxidation areas

Simple behavior of applying lotions or perfumes can not only moisturize the skin or add pleasant odors—it creates protective barriers to potentially harmful “oxidation fields” surrounding the body, according to new research published Wednesday in Science Advances.

Scientists at the University of California, Irving, the Max Planck Institute for Chemistry and Penn State have found that when skin oils interact with indoor ozone, daily personal care products can significantly reduce the concentration of highly reactive hydroxyl radicals formed around our bodies.

Previously unknown lotions and perfume benefits bring a surprising twist to our understanding of indoor air chemistry and our understanding of products for body applications, which can impact health beyond our health.

How your body creates its own chemistry cloud

When ozone, a common indoor air pollutant, is on our skin, especially the scaly ozone reaction, human oxidation fields form. This reaction produces hydroxyl radicals, which are extremely reactive molecules that are comparable to outdoor contamination levels at certain locations. These radical molecules can convert many compounds in the surrounding environment into new chemicals.

How powerful is this effect? In a ventilation chamber, a typical indoor ozone level is about 40 portions per billion, and a young person creates an oxidation field with a concentration of about 200,000 molecules per cubic centimeter, matching the levels found outdoors in a contaminated environment.

But what happens when we apply personal care products? That’s what researchers want to know.

Lotion and perfume produce chemical shields

The team conducted experiments on volunteers in a controlled room environment to measure chemistry with or without personal care products. They found two different mechanisms in their work:

• Body lotion creates a physical barrier between ozone and skin oil, reducing the production of hydroxyl radicals by diluting the skin oil component to 7% of its original concentration
• The ethanol solvent in the perfume acts as a large hydroxyl radical “sinking” to absorb these reactive molecules before interacting with other compounds
• Preservatives in lotions, such as phenoxyethanol, further help inhibit human oxidation fields
• Even pure essential oils can show some effect, although much less than alcohol-based perfumes

The science behind the shield

To understand how these products affect our field of personal oxidation, researchers have developed sophisticated computer models that track the movement and concentration of different chemicals around the human body in an indoor environment.

“Our team has adopted a unique approach to simulate the concentration of compounds near humans in indoor environments,” said Manabu Shiraiwa, a chemistry professor who jointly studied the study. “We have developed a state-of-the-art chemical model that simulates how ozone reacts with human skin and clothing, which may lead to formation [hydroxyl radicals] and semivolatile organic compounds. ”

These models suggest that the application of perfume may result in a decrease in hydroxyl radical concentration by as much as 86%, while body lotions can be reduced by 30-140% depending on the specific product and amount of application.

Why is this important for health?

These implications go beyond interesting chemistry. Studies have shown that these oxidation fields may affect the chemical composition of air in the respiratory region and may affect the compounds we expose in indoor environments.

“If we buy sofas from major furniture companies, we have tested harmful emissions before they are sold. But when we sit on the sofa, we naturally change some of them due to the oxidation areas we produce,” said lead author Jonathan Williams. “This can create many other compounds in our breathing areas, and their properties are not well studied. Interestingly, both body lotions and perfumes seem to reduce this effect.”

These findings are especially important considering that people spend up to 90% of their time indoors, where they use complex chemicals from their own bodies from furniture, cleaning products, cooking and now their own bodies.

Double-edged sword?

Researchers noted that while reducing the field of oxidation seems entirely beneficial, personal care products also introduce their own chemicals into the environment. The study notes that as of 2024, personal care products represent a $646.2 billion global industry, with widespread consumption affecting indoor and outdoor air quality.

The researchers believe that in some cases, chemical conversion caused by increased levels of hydroxyl radicals compared to precursors may produce products with reduced toxicity. However, the net consequences of elevated hydroxyl levels appear to be healthy indoor environments.

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This work was conducted as part of the Indoor Chemistry Human Emissions and Reactivity Project, bringing international collaborators together with computer modeling provided by the UC Irvine Indoor Chemistry Modeling Alliance. Both efforts received funding from the Alfred P. Sloan Foundation.

As researchers continue to uncover the complex chemical reactions of indoor environments, this study provides a study on how the products we use every day silently alter the air quality in our surroundings in previously unknown ways.

What other aspects of our daily work may significantly change our chemical exposure? This is a problem that future research needs to solve.