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Polyester Stinks More than Cotton Post Exercise, Research Shows

When it comes to odor in apparel, polyester wins for worst smell according to new research.

A recently published report by the American Society for Microbiology (ASM) showed that polyester clothing smells worse than cotton after intensive exercise because odor-causing bacteria grow better on the synthetic fabric.

In the study, researchers examined the T-shirts of 26 healthy individuals following an hour-long bicycle spinning session, incubated the shirts for 28 hours and then had them reviewed by a trained odor panel. Once odor molecules are released from a fabric, they come to our nose and we smell them. Sometimes the odor release is triggered by increasing temperature, like during a workout or while wearing a worn fabric again.

The report’s first author, Chris Callewaert of Ghent University, Belgium said the main culprit bacteria found on the clothing were micrococci, which are known for having a “typical malodor” and are able to grow better on polyester.

As activewear—largely made up of synthetics—storms the scene, these findings suggest consumers may want to lean toward cotton for workout wear, or that active apparel brands may need to ramp up efforts to incorporate alternative fabrics that still have performance traits.

Kim Kitchings, VP of corporate strategy and program metrics at Cotton Incorporated, said, “The active wear market has been dominated by synthetics for quite some time, but cotton is making inroads.” Kitchings also pointed to the ongoing success of Under Armour’s Charged Cotton line, which demonstrated that cotton can provide the moisture-management performance today’s consumers want.

Under Armour declined to comment on ASM’s research.

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Cotton Inc.’s research findings returned similar consulsions to ASM’s regarding the post-exercise scent of cotton versus polyester, and the organization has been working to increase cotton’s share of the athleticwear pie. Cotton Inc. is working on moisture-wicking technologies to tap into the market. The company’s TransDRY technology, for example, enhances cotton’s ability to move moisture away from the skin, without comprising softness or breathability.

“Our retail audits indicate that one-in-three athletic apparel items contains some cotton, but consumer preference for cotton in this category, combined with these findings on odor retention, may be what really moves the needle” Kitchings said.

Data from Cotton Inc.’s 2014 Sports Apparel Survey & Lifestyle Monitor show that 71 percent of consumers say they prefer their activewear to be made of cotton. According to the data, 94 percent of consumers said they would choose cotton activewear over synthetic activewear if cotton could wick moisture, regulate temperature (94 percent), be lighter weight (93 percent), hold or lock color (93 percent), resist UV rays (92 percent), and not show sweat (92 percent). Most shoppers also said they would be willing to pay a premium for cotton that could incorporate some of these performance traits.

Dr. Timo Hammer, head of research and bioservice for Hygiene, Environment & Medicine at research and testing institute, Hohenstein, said, “There are a lot of publications available dealing with the interaction of skin bacteria and fabrics and the ASM report is one piece of the jigsaw with an interesting differentiation of the bacterial flora on PES and cotton.”

Hammer said Hohenstein’s odor research goes a bit beyond as the institute looks at both the microbial aspect and how the odor molecules interact with different types of fiber. “We found that sweat odor molecules are stored better in cotton than in PES are therefore less accessible for the nose, which leads to reduced perceived odor. The decision if a fabric smells or not is made by the odor molecules which come to your nose rather than the bacteria producing the odoriferous substances.”

ASM’s Callewaert is still researching what about polyester encourages the odiferous bacteria’s growth, but said he suspects it has to do with the nature of the fabric’s surface.