Why do some clothes smell stronger than others?

Why do some clothes smell stronger than others?
Why do some clothes smell stronger than others?

Have you ever noticed that a polyester T-shirt smells worse after a workout than a cotton one? A new study from the University of Alberta shows why this is the case.

The analysis of various fibers soaked in a solution of artificial sweat showed that cotton and viscose (i.e. cellulose or plant fibers) absorbed and consequently released smaller amounts of odor-forming compounds than polyester, nylon and wool.

The study’s key finding explains why some commonly worn fibers smell stronger than others when people sweat, says Rachel McQueen, a clothing and textile scientist in the School of Agricultural, Life and Environmental Sciences who conducted the research with colleagues at the University of Otago in New Zealand.

“Although we know that polyester smells stronger when worn under 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.”

She points out that the method used in the study, which uses simulated liquid sweat, offers an important new approach to investigating the problem.

“Body odors usually get onto clothing through liquid sweat, but when studying odor retention in textiles, this exposure route is often neglected in testing procedures,” says McQueen, pointing out that traditional scientific methods only look at how the odor gets into the textile through the air. “If your armpits sweat and never touch the shirt you’re wearing, the fabric wouldn’t smell very strong.

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“By studying the transfer of odorants to textiles using a liquid sweat solution, we were able to provide a more realistic insight into how these odorants actually get into our clothes.”

In the study, researchers soaked the fibers in the sweat solution for different periods of time and then examined the release of various odor-causing compounds from these fibers using analyzers that can detect odors in the air in real time – similar to the human nose.

Overall, the study showed that the cellulose fibers absorbed smaller amounts of the compounds when passing through the sweat solution than textiles made of wool, nylon and polyester fibers, which in turn initially released larger amounts of the odorous compounds.

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

“While water-loving cellulosic fibers like cotton and rayon absorb more water from sweat than polyester, polyester doesn’t want to absorb the water,” notes McQueen. “It’s more oil-loving and absorbs more odorous compounds that don’t dissolve in water and more oily compounds that could also later decompose and stink.”

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

The study also showed that although nylon and wool initially absorbed many of the odors from sweat, they released them more quickly than polyester. After 24 hours, wool and nylon had a much lower odor intensity and were more similar to cellulose fibers.

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

Knowing more about why sweat makes some fibers smell worse could help consumers make more informed decisions when purchasing their clothes, she says.

“This is important not only for sportswear, but also for our everyday clothing,” she adds, pointing out that most of it is fast fashion with polyester content.

“If you’re worried about smelly clothes, you should generally stay away from polyester. Even if some clothing labels claim odor-inhibiting properties, be cautious. If the odor-inhibiting property is due to an antimicrobial agent, it may not be as effective as you think, because there is another mechanism at play that has to do with fiber chemistry and interaction with odorants.”

The study’s findings could also potentially be useful to textile scientists and manufacturers, for example in developing polyester that is more water-repellent and less likely to attract oily compounds, she adds.

Reference: McQueen RH, Eyres GT, Laing RM. Textile sorption and release of odorous volatile organic compounds from a synthetic sweat solution. Textilres J. 2024:00405175241249462. doi: 10.1177/00405175241249462

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