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Have you ever noticed that a polyester t-shirt is smellier than a cotton one after a workout? New research from the University of Alberta now shows why.

Analysis of various fibers soaked in a solution of simulated sweat showed that cotton and viscose, which are cellulosic or plant fibers, absorb – and therefore release – smaller amounts of odor-causing compounds than polyester, nylon and wool.

The main conclusion of the study, published in Journal of Textile Researchexplains why some commonly worn fibers are smellier than others when people sweat, says Rachel McQueen, a clothing and textile scientist in the Faculty of Agriculture, Life and Environmental Sciences, who conducted the research with colleagues at the University of Otago in New Zealand.

“Although we know that polyester is smellier after being worn to sweaty armpits compared to cotton T-shirts, we don’t really know why. We now have a better understanding of how fragrances are transported and selectively absorbed by different types of fibers in sweat.”

The study’s method of using simulated liquid sweat also offers an important new approach to studying the problem, she notes.

“Body odors are typically transferred to clothing via liquid sweat, but the study of odor retention in textiles often neglects this route of exposure in test procedures,” says McQueen, noting that standard scientific methods only involve examining how odor transfers through the air to the textile. “If you have a sweaty armpit that has never touched the shirt you’re wearing, then the fabric won’t smell much.

“By studying the transfer of fragrances to fabrics using a liquid solution of sweat, we were able to give a more realistic picture of how these odorous compounds actually get into our clothes.”

In the study, the researchers soaked the fibers in the sweat solution for different periods of time, then examined the release of various odor-causing compounds from those fibers using analytical equipment that can detect odors in the air in real time — rather like the human nose does.

Overall, the study showed that cellulose fibers took up smaller amounts of the compounds as they passed through the sweat solution than textiles made from wool, nylon and polyester fibers, which, conversely, initially released larger amounts. of the odorous compounds.

Sweat, which is mostly water, also has oily compounds that bacteria transform to form odors, McQueen explains. “These oil compounds and aromas in watery sweat can interact differently with textiles, depending on the chemistry of the fibers.

“While water-loving cellulosic fibers like cotton and viscose absorb more water from sweat than polyester, polyester doesn’t want to absorb water,” notes McQueen. “It’s oilier and absorbs more of the odors that don’t dissolve in water and more of the oily compounds that can also later break down and become smelly.”

The results of the study help explain why clothes made from cellulose fibers are less smelly than synthetic clothes after wear.

The research also showed that although nylon and wool initially absorb many of the odors from sweat, they dissipate them more quickly than polyester. After 24 hours, wool and nylon have a much lower intensity of aromas and are more similar to cellulose fibers.

“This tells us that while polyester still needs to be washed, for nylon and wool garments, people may be able to refresh them by simply airing them instead of washing them every time.”

Knowing why sweat makes some fibers smellier can help consumers make more informed choices when shopping for their clothes, she says.

“This has implications not only for exercise wear, but also for our everyday wear,” she adds, noting that most of it is fast fashion containing polyester.

“Basically, if you’re concerned about smelly clothes, then stay away from polyester. Even with some of the anti-odor claims on some clothing labels, you may want to be cautious. If the anti-odor property is due to an antimicrobial agent, it may not be as effective as you think because there is another mechanism that has to do with the chemistry of the fibers and the interaction with the aromas.”

The study’s findings could also potentially be useful to textile scientists and manufacturers, perhaps in developing polyester that is more hydrophilic and less attracted to fatty compounds, she adds.