Textile scientists offer new insights into why some clothes smell stronger

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

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

The main conclusion of the study, published in the Journal of Textile Researchexplains why some commonly worn fibres smell more than others when people sweat, says Rachel McQueen, a clothing and textile scientist in the School of Agricultural, Life and Environmental Sciences who led the research with colleagues at the University of Otago in New Zealand.

“While we know that polyester smells stronger when worn near sweaty armpits than cotton T-shirts, we don’t really know why. We now understand better how odors are selectively transmitted and absorbed by different types of sweat fibers.”

The study’s method, which uses simulated liquid sweat, also offers an important new approach to exploring the question, she notes.

“Body odor is typically transferred to clothing through liquid sweat, but studies of odor retention in textiles often overlook this exposure pathway in testing procedures,” McQueen says, noting that standard scientific methods only include examining how odor moves from air to textile. “If you had a sweaty armpit that never touched the shirt you were wearing, then the fabric wouldn’t smell much.”

“By studying the transfer of odors to fabrics using a liquid sweat solution, we were able to provide a more realistic insight into how these odorous compounds actually penetrate our clothes.”

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

Overall, the study showed that cellulosic fibers absorbed smaller amounts of compounds when transferred through the sweat solution than textiles made from wool, nylon, and polyester fibers, which, conversely, initially released higher amounts of odorous compounds.

Sweat, which is mostly water, also contains oily compounds that bacteria convert to form odors, McQueen says. “These oily and odorous compounds in aqueous sweat can interact differently with textiles, depending on the chemical composition of the fibers.”

“Water-loving cellulosic fibers like cotton and viscose absorb more water from sweat than polyester, but polyester doesn’t want to absorb water,” McQueen notes. “It’s more oil-loving and absorbs more odors, which don’t dissolve in water, as well as oily compounds, which could also break down later and become smelly.”

The study results help explain why clothing made from cellulosic fibers tends to smell less than synthetic clothing after being worn.

The study also showed that while nylon and wool initially absorbed a large portion of the sweat odors, they dissipated them more quickly than polyester. After 24 hours, wool and nylon had much lower odor intensities and were more similar to cellulosic fibers.

“This tells us that while polyester should always be washed, nylon and wool garments can be refreshed simply by airing them out rather than washing them every time.”

Learning more about why sweat makes certain fibers smell more can help consumers make more informed choices when purchasing clothes, she says.

“It’s not just sportswear, it’s also our everyday clothes,” she adds, noting that most of these clothes are fast fashion containing polyester.

“Basically, if you’re worried about your clothes smelling bad, avoid polyester. Even though some clothing labels claim anti-odor properties, you should be careful. If the anti-odor property is due to an antimicrobial, it may not be as effective as you think because there’s another mechanism at play, which involves fiber chemistry and interaction with odorants.”

The study’s results could also be useful to scientists and textile manufacturers, perhaps to develop a polyester that is more hydrophilic and less attracted to oily compounds, she adds.