“Does a runner stink after a workout?” is akin to the old adage “Does a bear sh*t in the woods?” Of course runners stink! Apparel has come a long way since the running days of yore, when runners donned cotton that soaked up sweat, caused chafing, and was hardly breathable. But with the development of technical fabric, like polyester, came the stench from a 20-miler.
“It’s not actually the sweat that smells,” says Matt Taylor, CEO and founder of running apparel company, Tracksmith. “Synthetic fabrics like polyester are the perfect breeding ground for odor-causing bacteria.”
In an effort to combat runner stink, companies turn to two methods: developing gear that uses naturally odor-resistant materials like merino wool or enlisting antimicrobial additives made from a variety of chemicals and compounds.
Activewear brands often embed Swedish-based Polygiene technology, which uses silver chloride (silver salt) to fight odor. As with all antimicrobial additives, there’s concern about long-term health and environmental risks. (Silver nanoparticles in clothing, for example, enter the water system during washing.) While Polygiene tech is EPA-approved, some experts argue that the additives need to be studied more extensively to rule out negative impacts.
A 2013 study published in Environmental Science & Technology looked at activewear that used silver nanoparticles for its antimicrobial properties. Researchers found that while the chemicals did rub off on skin, this is likely less worrisome than applying creams containing the same silver nanoparticles, such as some sunscreens. (Ingesting the particulates can lead to significant DNA damage, according to research from MIT and Harvard’s School of Public Health.) The problem is that when it comes to these concerns, we don’t know how much is too much.
Then there’s merino wool, which, while more expensive than synthetic fabrics, is naturally anti-odor (and also super soft, breathable, and moisture-wicking). Because of these features, merino has become the gold standard in athletic wear.
“Merino doesn’t allow bacteria to colonize, thanks to the thread’s shape and texture,” Taylor says. “It’s very different from polyester, which has a smooth surface area that allows bacteria to grow.” Not unlike a petri dish.
Some brands, including Tracksmith, use both merino and Polygiene in select items; Tracksmith’s merino-blend Brighton Base Layer has stood the test of time in durability and fresh scent because of wool’s natural odor-fighting properties. Just take note that products treated with antimicrobials like Polygiene will start to lose their anti-stink capabilities over multiple washes.
Do’s and Don’ts of Activewear Care
- Rinse or air out your gear immediately after a run. “Hop in the shower with your shorts on. You’ll immediately address the sweat that’s trapped in the fabric,” Taylor says. Deputy test editor Jeff Dengate swears by this practice, too.
- For stinky gear, wash as soon as you can with detergent. Be sure to follow bottle instructions on how much to use; sports gear-specific detergent is highly concentrated, meaning you don’t need to use as much as the regular stuff.
- Follow the care instructions on the garment label.
- Put your gear in the dryer. “Natural fibers like merino and cotton will shrink in the heat,” Taylor says. “Most synthetic fabrics can withstand high heat, but it can impact anything bonded, like artwork, on your favorite race shirt.”
- Wash your anti-odor gear after every run. While the benefits of merino won’t fade with washing, treated clothing only lasts about 50 washes before the anti-odor features break down. (Plus, the less you wash, the less water and chemicals you use, which is good news for the environment.)
Gear That Stays Fresh Mile After Mile
We put these items through the paces on back-to-back-to-back-to-back runs without washing. I wore each piece of gear for no fewer than three consecutive workouts, ranging from easy runs to speedwork to 10-milers. Then each item went into the wash at least once.
Tracksmith Session Speed Shorts
Shorts can stink, especially if you run commando. The Polygiene liner in these shorts doesn’t totally avoid postrun smell but helps mitigate it, something Taylor acknowledges. And the airy fabric of the shorts keeps things breezy, compared with tights or compression-style shorts.
Title Nine Phoenix Pleat Back Long Sleeve Top
This loose-fitting top is breathable and fights odor with its StinkStopper technology—a Polygiene-based fabric. The top, which has a decorative pleat along the back, runs big. (For warmer months, this comes in a tank style.)
Ibex Balance Sports Bra
Ladies, you can wear all the merino base layers you want, but if your sports bra isn’t merino, your stuff still might stink. This bra is designed for medium impact, but this tester’s 34A chest felt supported and comfortable on long runs and during speed work. It’s been on five sweaty runs, including two 10-milers, and still doesn’t smell.
Hoka Merino Blend Short Sleeve
Even for the stinkiest of runners, this top stays fresh after multiple wearings. It’s a lightweight base layer that can sit on its own or provide a layer of warmth and anti-odor under heavier gear, thanks to its 67 percent merino fabric.
Smartwool Hat Go Far, Feel Good Runner's Cap
For $35, we’d expect the entire cap to be made of merino wool, but it’s just the interior band around the crown. This does seem to do the trick, though, for fighting odor and swampiness. It’s spot-clean only, which raises some eyebrows for a piece of running gear. That said, the hat withstood a machine wash and still smells fresh.
The Lowdown on Detergent
Eventually you have to wash your clothes (especially the ones that aren’t anti-odor). Your best bet for the environment is to wash your clothing with cold water. As for detergent? Antimicrobial and antibacterial chemicals can be cause for health concern. For example, ammonium chloride can be found in both fabric protectors and some laundry detergents.
The Environmental Working Group—a nonprofit that focuses on public education regarding toxins in cleaners, cosmetics, and other consumer products—is a helpful resource to evaluate your detergent’s ingredients and safety (ewg.org).
An OG in sportswear detergent, Win is certified as a “Safer Choice” by the Environmental Protection Agency, which means it uses better ingredients for health and the environment
Sweat X Sport Activewear Detergent
This highly concentrated formula is our go-to for stinky AF shorts. But instead of washing the whole load with it, dab a little inside the shorts and then wash with regular “free and clear” detergent, which limits exposure to known irritating additives.
Hex Performance Deodorizing Spray
This brand has a line of detergent and detergent-adjacent products. The spray is basically Febreze, and while it masks the smell, it’s not actually cleaning anything. Instead, spritz and let dry if you must re-wear a pair of gross shorts and don’t have time to wash. (Note: Hex does not include its ingredients on its bottles, merely stating “water, surfactants, and preservatives.”)