Textile scientists provide new insights into why some garments become smellier

Ever notice that a polyester T-shirt stinks more than a cotton one after you work out? 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, cellulose fibers or vegetable fibers absorbed and then released smaller amounts of odor-causing substances than polyester, nylon and wool.

The main finding from the research, published in the Textile research journalexplains why some commonly worn fibers become more odorous than others when people sweat, says Rachel McQueen, an apparel and textile scientist in the Faculty of Agricultural, Life and Environmental Sciences who conducted the research with colleagues at the University of Otago in New Zealand.

“While we know that polyester smells worse after wearing next to sweaty armpits compared to cotton T-shirts, we didn’t really know why. Now we have a better understanding of how odorants are transferred and selectively absorbed by different fiber types in sweat.”

The study’s methodology, which uses simulated liquid sweat, also offers an important new approach to investigating the problem, she notes.

“Body odor is often transferred to clothing via liquid sweat, but research into odor retention in fabrics often ignores this route of exposure in testing procedures,” says McQueen, who notes that standard scientific methods only involve examining how the odor travels through the air to the fabric. “If you had a sweaty armpit that never touched the shirt you were wearing, the fabric wouldn’t smell very bad.

“By studying the transfer of odorants to fabrics using a liquid sweat solution, we were able to gain a more realistic understanding of how these smelly compounds actually end up on our clothes.”

In the study, the researchers soaked the fibers in the sweat solution for varying amounts of time. They then examined the release of various odor-causing compounds from those fibers using analytical equipment that can detect odorants in the air in real time, much like the human nose.

Overall, the study showed that the cellulose fibers picked up less of the compounds as they were transported through the sweat solution than textiles made from wool, nylon and polyester fibers, which in turn initially released larger amounts of the smelly compounds.

Sweat, which is mostly water, also contains oily compounds that bacteria convert into odors, McQueen explains. “These oily compounds and odorants in the watery sweat can interact with textiles in different ways, depending on the fiber chemistry.

“Although water-loving cellulose fibers like cotton and viscose absorb more water from sweat than polyester, polyester doesn’t want to absorb water,” McQueen notes. “It’s more oil-loving and will absorb more of the odor compounds, which don’t dissolve in water, and more of the oily compounds, which can also break down and smell later.”

The study results help explain why clothing made from cellulose fibers generally smells less after wearing than synthetic clothing.

The study also showed that although nylon and wool initially absorbed much of the odor from sweat, they dispersed it more quickly than polyester. After 24 hours, wool and nylon had much lower intensities of odor and were more similar to cellulose fibers.

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

If consumers know more about why sweat causes some fibers to smell, they can make more informed choices when buying clothes, she says.

“This is not only important for sportswear, but also for our everyday clothes,” she adds, stressing that most of the clothing is fast fashion and contains polyester.

“If you’re concerned about your clothes smelling bad, stay away from polyester. Even with some anti-odor claims on some clothing labels, you may want to be careful. If the anti-odor property is due to an antimicrobial agent, it may not be as effective as you think because there’s another mechanism at play, namely the fiber chemistry and its interaction with odorants.”

The research findings could also potentially be useful to textile scientists and manufacturers, for example in developing polyester that is more resistant to water and less attracted to oily substances, she adds.