Why Does Synthetic Athletic Clothing STINK?

Why Does Synthetic Athletic Clothing STINK?

Susan Wiczynski

We Love Synthetic Workout Gear but Hate the Stink!

This morning, I plucked a freshly washed 100% polyester workout jersey off my shelf and pulled it over my head in anticipation of trotting off to my favorite exercise class smelling like a comforting fairy cloud of warm clover mixed with sea cotton, rainbows, freesia, and kittens.

Which I did. Until I settled into my car, which was cozy and warmed by the soft, early fall morning sun. As the temperature in the car rose, I grew uneasy. Something was starting to smell a little off. That’s not unusual; it’s an 11 year old minivan with a generation of a skittles, goldfish, and tootsie rolls mummified into the carpets. But this was a different bad, a… personal… bad. I sniffed an arm. In place of the clover/cotton/rainbows/kittens was the unpleasant, yet familiar, aroma of Old Workout Clothes. I hadn’t even broken a sweat yet. UGH!

Athletic Apparel Is Supposed To Make Us Feel Good About Ourselves….

We start our relationship with synthetic athletic clothing with such high hopes. Comfortable, drapey, colorful, stretchy (and also, ahem, problem-area-hiding)  jerseys, tops and compression-wear bottoms beckon us from their packages and hangers, and when we try them on, we feel like Venus Williams or Ronaldo. I AM STRONG! I AM COMPRESSED! I AM ATHLETIC!  ARRGHHH [pirate noise]!!

… But Synthetic Fabrics Don’t Stay Fresh

Reality, however, sets in after the first workout or game. After a few hours sprinting back and forth across a soccer field, pounding a volleyball, or hiking up a hot hill, we now have -- as the famous douche commercial from 1990 informed us in wide-eyed innocence --  that “not so fresh feeling.”

Into the laundry the offending garment goes, but…. no matter what detergent we use, or what temperature water we wash it in, or how many times we rewash it, a funk starts to settle into the fabric. This is not a well-behaved funk either: it teases us with freshness when we glide the newly washed garment onto our bodies, but minutes later, when we heat up or break a sweat, our new friend is suddenly a nasty, stinky old backstabber. Sometimes, it doesn’t even take perspiration to activate the odor: leaving a washed polyester jersey in a drawer for a few weeks can render it sour before it’s even pulled over ones head.

For some synthetic athletic clothing, it seems no amount of washing will get the stink out.

Having owned a uniform company for a number of years, and now owning a company that caters to female athletes, and, frankly, as an active person myself, I have always wondered why this is.

What Is Synthetic Fabric?

Back in the day, people wore cotton, silk, leather, fur, or wool, as these were readily available fibers from plants and animals. Polyester was invented in the 1930’s, but it wasn’t until the early 60’s that it began to be used widely in fashion. Polyester is essentially plastic fabric that’s derived from petroleum: it is heated, combined with other chemicals, and stretched into thin threads, which are woven and knitted into fabric. By the 1970’s, polyester clothing was a big hit with the leisure suit crowd. It’s cheap, wicks moisture, repels stains, stretches nicely, and doesn’t wrinkle, shrink or fade (or, unfortunately decompose). Such a miracle fabric right?

Polyester has lots of trade names now, and many different formulations and combinations, but most jerseys and workout tops and bottoms are made from some version of this synthetic fiber.

How I Became Interested In Synthetics vs. Cotton 

I owned a company that manufactured uniforms -- scrubs, drawstring pants, and lab jackets --  for nursing school students. In the course of their 2-4 year nursing programs, students practice not only in hospitals but also in the community with their mentors and teachers. Many of our school clients asked us to provide a polo shirt as well as scrubs so that the students would look professional for their community work. We weren’t set up to sew polo shirts, so I needed to find a source.

Back in the early 2000’s, most polo shirts were sized for men, but most nursing school students were women, so I had to do a lot of research on where to find the best polos for our student clients. The polos needed to look nice (as the students were representing their school in public) and to be durable. They also needed to be affordable.

I finally found a company that imported 100% cotton polos in women’s cuts and sizes and in lots of colors for a reasonable price. The nursing schools were excited, and we began selling them to many of our contracted programs, often embroidering the school logo onto the chest.

Alas, a few months into the school year, the phone calls started: “The polos used to fit our students,” a dean of nursing would tersely begin, “but now they are coming to class wearing what look like crop tops!” The smaller sizes in particular shrank a lot.

How embarrassing for us all! Good bye cotton, my old friend.

The hunt began anew, and I ordered all kinds of polo samples from several companies, asking my employees to wear them around and wash them so we could see if they were durable enough. I remember my general manager telling me that she liked everything about her sample, except, well, the armpits REALLY smelled bad, even after laundering. I asked around, and all of the employees who had taken home polyester samples had the same problem. We ended up settling on a cotton/polyester blend.

Armpits 101

Humans perspire in three ways: through eccrine glands, which are found all over the body and secrete water and electrolytes to help keep us cool, apocrine glands, which emit oils in hairy areas and react to emotion, and apoeccrine glands, which are in areas of apocrine glands but secrete watery fluids similar to eccrine glands. So if you feel extra smelly after an anxious experience such as public speaking, that’s because the apocrine glands’ oily sweat was designed by nature to produce a scent (pheromes even!)  -- perhaps to help early humans identify each other or be attracted to (or repulsed by) a potential mate. The armpit and groin is full of these little buggers, and the sweat they produce is odorless until it comes into contact with bacteria.

When we exercise, we heat up, and our sweat cools us. Bacteria love warm, moist areas, and they break down certain proteins in the sweat into acids -- which is why the sweat on our bicep or ankle doesn’t smell bad, but under our arms or in other nether regions, we get stanky.

Why Does Polyester Trap Odors But Cotton Doesn’t?

In a word, absorbency. Cotton fibers absorb up to 27 times their weight in water, making them “hydrophilic” (hydro = water and philic = love). Which is why it's not a great idea to wear cotton if you know you will be getting wet or sweaty in cold conditions, because you will STAY wet or sweaty and get chilled. But cotton is a simple chemical structure, allowing laundry water and detergent to flow through and remove the bacteria that cause the odors. Thus, cotton clothes, no matter how foul, can emerge from our laundry like sweet, fresh friends.

Polyester synthetic fabric, being plastic, is “hydrophobic,” meaning it repels water. BUT! Oily sweat from your pits (etc.)  -- B.O., if you will --  is sticky and gets into the nooks and crannies of the plastic fibers that make up polyester and STAYS THERE. Water doesn’t flush well through hydrophobic materials, and bacteria get trapped. It’s like trying to rinse a salad dressing bottle with plain water. The old dressing just sticks to the glass.

Worse, we often add extra detergent or fabric softener to rank laundry loads thinking it will help get rid of the odor, but -- unlike salad dressing and glass -- polyester traps the detergent and softener molecules too. You’re not going to want to hear this, but over time these trapped molecules essentially rot. If you have ever washed a microfiber or polyester jersey and hung it to dry but accidentally left part of it scrunched, so that it took longer to dry in that one area, you may have noticed that the folded area was more sour than the rest of the garment.

This unpleasant phenomenon happens to me on winter days. An avowed laundry hippie, I hang our family’s clothes outdoors unless it is cold and rainy, in which case I use racks inside. If the loads are big, or the weather is especially moist, it can take a long time for those clothes to dry indoors completely, and anything that’s synthetic can end up smelling as bad as it did before it was washed. Sigh!

How To Wash Synthetic Athletic Clothes So They Smell Fresh

The idea is to allow as little bacteria as possible to form in your clothes in the first place, and then to get it out so it doesn’t continue to create bad smells.


  1. Take a quick washcloth “shower” before you work out: pits, tits, and cracks.

  2. Wash garments right away, or at the very least let your synthetic athletic clothing dry before throwing in a hamper. Turn your gear inside out so the sweaty bits are more easily accessed by the cleansers.

  3. Add ½ - 1 cup of white vinegar to your load. Don’t worry, you won’t smell like a salad, but vinegar, containing acetic acid, can help break down the stink-producing bacteria. It can be used to strip detergent buildup in towels too, by the way..

  4. Air dry outdoors in the full sun if possible, leaving space between items and avoiding folds. Sunshine kills bacteria. If you must use the dryer, use a very low heat setting.

  5. Make sure synthetic fabrics are 100% dry before putting them away.


  1. ...use extra detergent or fabric softeners. Less is more, and all the extra perfumes, dyes, and coatings will just add to the whole bacteria party going on in your jerseys.

  2. ...use Borax with vinegar. While Borax can be used to raise the pH of your wash water to treat acidic stains like tomatoes, vinegar is a pH lowerer -- so they will cancel each other out.

  3. ...dry on high heat. This will just bake in the smells and stains.

  4. ...leave your clothes in the dryer when it stops, in case there is a bit of moisture left.

  5. ...bother with specialty gymwear detergents. You probably won’t need them if you follow the directions above.

Or you could switch back to cotton.

Happy workout!

Leave your comment
11/8/2021 2:40 PM
I have wondered this for years! Thanks for an informative and practical post!  I've had success with soaking extra-stinky items in vinegar, but it's an extra step so I almost never do it.  Will try adding it to the washer as you suggest!