Skinny On

Smelly Sports Clothing

Smelly Sports Clothing
By Hannah Holmes

Ah, the outdoor life! The sun on your face, the taste of a mountain stream, the powerful scent of the shirt you wore yesterday, lethal enough to level an acre of virgin forest ...

It's a double-edged sword, that high-performance long underwear/biking/running "poly-pro" stuff made from petrochemicals and magic. Some breeds are more double-edged than others. Some breeds could scare the edge off a Swiss Army Knife blade.


How come? And how come ye olde cotton T-shirt never smells quite so ... hideous?
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The official response from makers of synthetic fibers seems to be along the lines of, "Pshaw." One spokesperson told me the reason polypropylene clothing reeks so insanely is that polypropylene dries so quickly that your random dumb jock will put it on for a second workout without washing it, whereas a used cotton shirt will stay so clammy and damp that the athlete wouldn't dream of climbing into it twice. Plausible as that sounds, it turns out the "Pshaw" theory isn't entirely correct.

"Well, I'm taking your word for it that the synthetics smell worse," says Kay Obendorf, Ph.D., a textile chemist at Cornell University. "I've never made a study of that. But there are some possible explanations for why it might."


For starters, let's talk about the charms of synthetic fibers.
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Yeah, they're tougher than cotton fibers, and take more abuse. But their real selling point is that they are hydrophobic -- they hate water. A cotton fiber is a lush -- swilling sweat like there's no tomorrow -- then holding it close to your body where its slow evaporation chills you. A plastic fiber is a teetotaler. The water stays on its surface, and your body heat pushes the sheath of water down the fiber and out to where the air can whisk it away. (In jock parlance, this is called "wicking.")

Now let's talk sweat. There are two kinds. Eccrine sweat is 99 percent water, with a pinch of salt and urea added. But in times of stress, your armpits and groin release a second, oily type of sweat, apocrine, which is loaded with interesting things, including protein, carbohydrate, ammonia and fatty acids.


Bacteria, who slurp up sweat and turn it into a variety of gaggy odors, eat both kinds, but they especially like the fats in apocrine sweat.
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Joining the two sweats on the skin is sebum, another fatty secretion designed to protect your skin. Because sebum melts in sweat, all these groceries migrate together across your skin and into your clothes.

Now let's talk oxidation. Some fats from sebum and sweat stick to your clothes and oxidize there, turning yellow and smelling rancid. Your old pillowcases bear the yellowing sebum from your greasy face, says Obendorf. Likewise the yellow armpits of white shirts: oxidized fat.

Then there's laundry. The same person who suggested that dumb jocks equate dry synthetic clothing with clean synthetic clothing also suggested that dumb jocks also don't know how to do laundry -- that on that rare occasion when we do toss our smellies in the machine, we're following the instructions so haphazardly that the oils and bacteria hold their ground.

OK, fair point. But chemistry's involved, too. Remember the oil-and-water thing? Like substances mix; un-like ones don't.

"These body oils are hydrophobic," says Obendorf. They don't like water either. "If you wash a hydrophobic fabric soiled with these hydrophobic oils, you're going to get less-than-complete cleaning, because they tend to like each other. It's easier to launder oils off a hydrophilic fiber like cotton." Furthermore, Obendorf says, since synthetics don't absorb liquids, the sticky oils may collect on the fiber surface, where they're more vulnerable to the odoriferous onslaught of oxidation.

So could a person of normal IQ conceivably wash a polypropylene shirt, wear it for an hour and be re-wrapped in a pall of putridity? Yes and no. Obendorf says pre-treating, hot water and extra detergent all help. A quick swish in a mountain stream, incidentally, provides none of these.


Vocabulary

chromidrosis, n. Thanks to rare malfunctions, the human body can actually sweat in color. Greenish and yellow-brown are possible, and leaking blood vessels can result in red sweat.


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  • Why Teflon Sticks to the Pan
  • Lunacy and the Full Moon
  • Sunscreen Testing
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    Hannah Holmes is a writer in Portland, Maine, who knows about sweat. She just spent a month -- including three weeks without a shower -- in Mongolia's Gobi Desert reporting for Discovery Online's Dinosaurs in the Dunes special. She also writes for Escape, Outside, Sierra, Backpacker, Eco Traveler and Women's Sports and Fitness. Send her a note at skinny@online.discovery.com.


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