Perfume and Lotion Can Disrupt the Human Oxidation Field

A spritz of perfume or an application of lotion may interfere with the highly reactive chemicals surrounding the body, new research suggests, with health consequences that remain unknown.

This chemical layer, called the human oxidation field, is believed to react rapidly with nearby molecules and neutralise certain volatile compounds.

However, a new study indicates that applying perfume or lotion to the skin can alter the chemistry of the immediately surrounding air. This could allow toxic chemical byproducts to rise towards the nose or be absorbed through the skin.

"Given that the human oxidation field influences the chemical composition of air in the breathing zone and close to the skin, it affects our intake of chemicals, which, in turn, affects human health," says Max Planck Institute atmospheric scientist Nora Zannoni and colleagues.

The human oxidation field

Scientists still know relatively little about the human oxidation field or its effects on health. It was only discovered in 2022, when a team involving several of the same researchers found that skin oils react with ozone pollution in the air, creating a field of hydroxyl (OH) radicals around the body.

OH radicals are sometimes called an atmospheric ‘detergent’ because they are able to react with and neutralise a broad range of pollutants in the air.

Yet some of these reactions could also create potentially harmful byproducts immediately beside the skin and airways.

Understanding how the human oxidation field responds to chemicals in indoor and outdoor settings is an emerging area of health research.

Lotion and fragrance disrupt surrounding chemistry

For the new research, four young adults sat in a temperature-controlled indoor space while scientists measured chemicals around their bodies and in the air, both with and without personal care products having been applied.

When some volunteers had put on lotion shortly before entering, the researchers observed two chemicals - phenoxyethanol and ethanol - moving upwards from their skin in ‘thermal plumes’. Carried by body heat, these plumes dispersed the chemicals into the surrounding air.

Levels of the lotion-derived chemicals around each participant kept rising steadily, including 10 minutes after application. Concentrations close to the nose, for example, were 2.8 times greater than those in the ambient air.

The researchers then introduced ozone through an inlet in the floor beneath the participants. Ozone forms when sunlight reacts with volatile organic compounds and, although concentrations are higher outdoors, it can enter buildings and react with skin oils to produce a human oxidation field.

They found that body lotion reacted with the human oxidation field across the entire body. It hindered ozone’s production of an important OH precursor, cutting its concentration around participants by 34 percent.

A comparable effect was seen when participants applied fragrance to the backs of their hands before entering the controlled room.

Ethanol and monoterpenes both increased around the participants, reaching concentrations 10 times higher above their heads than in the surrounding ambient air.

These substances also reacted with the OH radicals around the body, lowering their levels within the oxidation field.

"This study has determined that the human oxidation field generated by people exposed to ozone indoors is substantially disrupted when personal care products are worn," write the authors.

Potential health effects remain unclear

The team examined chemical changes around the human body rather than health outcomes, but the volatile reactions taking place nearby concern the researchers.

"We need to rethink indoor chemistry in occupied spaces because the oxidation field we create will transform many of the chemicals in our immediate vicinity," said atmospheric chemist Jonathan Williams, project leader of the 2022 study that discovered the human oxidation field.

"OH can oxidize many more species than ozone, creating a multitude of products directly in our breathing zone with as yet unknown health impacts."

The study was published in Science Advances.