University of Alberta scientists have used science to figure out why sweat makes some clothes stink more than others.
U of A textile scientist Rachel McQueen co-authored a study last May on how textiles interact with odorous volatile organic compounds (VOCs) in synthetic sweat. The study was the latest in a series of studies she had done on why sweat makes some fabrics smellier than others.
Sweat is made of water, salt, and various oily substances that turn into smelly VOCs, McQueen said. While some of these compounds raise a stink when microbes eat them — hence the popularity of antimicrobials as odour reducers — others are directly smelly and can build up on fibres over time.
Most previous studies of clothes and odours tested how smelly substances move from the air onto fabric, McQueen said. Her team wanted to use artificial sweat to see how liquids affected this transfer. Using fake sweat instead of the real stuff let them precisely track the amount of each smelly substance that their test fabrics absorbed and released.
McQueen’s team took fresh threads of cotton, mercerized cotton, viscose, wool, nylon and polyester and soaked them in bottles of fake sweat made with salty water and smelly VOCs present in body and laundry smells. They then sucked out the excess sweat, put the threads into sealed vials, and let them sit for 24 hours. The team used a proton transfer reaction mass spectrometer to track what VOCs the threads released over time.
The team found that the cotton and cotton-like fibres in the study absorbed and subsequently released the least VOCs of the fabrics tested. Polyester absorbed and released the most. Nylon and wool were initially stinky, but were about as smelly as cotton after 24 hours.
It’s all chemistry
McQueen said fibre chemistry explains why the polyester stunk the most. Cotton is hydrophilic (water-loving), so it’s more likely to absorb water and not the oily, non-soluble VOCs in sweat, making it less likely to hold onto smelly substances.
“Polyester actually repels water,” McQueen said, which makes it grab onto oily substances and resist attempts by clothes-washers to pull them away.
“It almost intensifies the odour,” she said, and makes the clothes smellier over time.
Sturgeon Valley Athletic Club fitness manager Danielle Smith (not the Alberta politician) said she has also noticed that her cotton-based athletic clothing smells better and lasts longer than her polyester clothes.
“I’ve got cotton fitness wear I’ve had for 10 years and I’m able to take care of it and it doesn’t have an odour,” she said, whereas her polyester wear becomes too smelly to use after six months.
Smith recommended using Power Wash or Ecos detergent to wash smelly clothes. Soaking them in vinegar and baking soda also works.
McQueen said the fact that the nylon and wool released odours more quickly than the polyester suggests that we could reduce their smelliness by airing them out on occasion, reducing the need to wash them.
McQueen said this study suggests that people worried about stinky clothes should stick to garments made out of natural fibres such as cotton that are less likely to absorb the oily substances in sweat. If you wear polyester in hot weather, “you’re just going to have to accept that it’s going to get a bit stinkier.”
McQueen’s study (“Textile sorption and release of odorous volatile organic compounds from a synthetic sweat solution”) can be found in the OnlineFirst archives of Textile Research Journal.
