Why do polyester clothes stink more than cotton?

Have you ever tossed off that sticky polyester T-shirt at the end of a long workout session, only to be accosted by a nasty, lingering odor that seems to be more intense than that of your cotton ones?

Thanks to some insightful research rolling out from the University of Alberta, we now have the nose-crinkling answer to this mystery.

Working tirelessly to unravel the secrets behind smelly gym clothes, is Rachel McQueen, a seasoned textile scientist from the Faculty of Agricultural, Life & Environmental Sciences.

Partnering with her peers from New Zealand’s University of Otago, Rachel McQueen led the charge to find out why some textiles stink more than others when we sweat.

Odor on polyester and cotton

Drilling into the heart of the matter, the team analyzed how various fibers — cotton and viscose (both plant-derived or cellulosic fibers), along with polyester, nylon and wool — interacted with a simulated sweat solution, which could result from exercising.

The result? Cotton and viscose soaked up fewer odor-causing compounds, releasing less funk than their polyester, nylon, and wool counterparts.

“Although we know that polyester is smellier after being worn next to sweaty armpits compared to cotton T-shirts, we haven’t really known why,” explains McQueen.

“Now we have a better understanding of how odorants transfer and are selectively absorbed by various fiber types in sweat.”

This study, which uses a simulated liquid sweat method rather than just examining how odor passes through the air, basically paints a clearer and more realistic picture of the stink transfer.

Science behind polyester and cotton

Sweat is mostly water, but it also contains oily compounds, which bacteria help transform into odors. These compounds can interact differently with various textiles, depending on their fiber composition.

For example, water-loving fibers like cotton and viscose soak up more sweat water, while polyester, which leans toward the oily side, absorbs more odorants that aren’t water-soluble, along with those potentially odorous oily compounds.

This explains why garments made from cellulosic fibers like cotton, viscose, and perhaps bamboo, end up less smelly when compared to synthetic clothing after you’ve worn them for a bit.

“Body odors commonly transfer to clothing through liquid sweat, but investigation of odor retention in textiles often neglects this route of exposure in test procedures,” McQueen says.

If you had a sweaty armpit that never actually touched the shirt you’re wearing, then the fabric wouldn’t get very smelly.

By studying the transfer of odorants to fabrics using a liquid sweat solution, we were able to give a more realistic insight into how these smelly compounds really get into our clothes.

Wash or air out? That’s the question

The study also reveals some interesting insights about nylon and wool clothing. Apparently, while these fabrics initially absorb a lot of the odor-causing compounds, they also dissipate them faster than polyester does.

After 24 hours, both wool and nylon have much lower odor intensities, similar to the less-smelly cellulosic fibers.

So do you need to pop your nylon and wool gym clothes into the washer after every workout? Not necessarily!

McQueen suggests, “You might be able to freshen them by just airing them out rather than laundering every time.”

Impact on consumer choices

McQueen stresses that these findings are not just relevant for gym wear but for all clothing, especially considering how much of our daily wear is made from polyester.

“If you’re concerned about smelly clothes, steer clear of polyester,” she advises.

“While water-loving cellulosic fibers such as cotton and viscose absorb more of the water from sweat than polyester does, polyester doesn’t want to absorb the water,” McQueen notes.

It’s more oil-loving, and it absorbs more of the odorants, which don’t dissolve in water, and more of the oily compounds, which could also later break down and become smelly.

The study findings are also potentially beneficial for textile scientists and manufacturers. Perhaps the answer to less smelly polyester lies in making the fabric more water-attracted and less oil-loving.

So, the next time you’re shopping for workout clothes or just browsing for casual wear, will you think twice before reaching for that polyester tee?

The study is published in the journal Textile Research Journal.

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