Is It OK To Re-Wear Your Dirty Workout Clothes?

Posted on February 17 2017

"If I wear my Physiclo resistance tights during a distance run on Monday, can I just air it out and wear it again for my gym session on Tuesday?"

It's a question we get asked pretty frequently.

Washing your favorite workout gear after every use isn't always practical, especially if you have to cough up $2.50 per wash. If you didn't work up much of a sweat (and it's only *cough* slightly dirty), it's not a big deal to just re-wear it for one more workout right?

As someone with a background in biomedical engineering and medical school, here's my take:

The short answer is no, it's not recommended to re-wear your workout clothes because bacteria and yeast tend to rub off onto your clothing, especially after you sweat.

When you put the dirty clothes on again the next day, the bacteria will have multiplied (as bacteria do), which leads to smellier odors and potentially skin irritation or infection.

The longer answer though, is that it's actually not bad ALL the time- it depends on quite a few factors, such as how much you sweat in the clothes, whether you stuffed it in a hamper or left it out, and even the type of fabric.

Different fabrics tend to collect different types of bacteria (e.g. polyester tends to house micrococcus, while cotton is more prone to collecting staphylococcus). This can be significant because micrococcus in polyesters can cause more rank odors but rarely cause infections.

Different fabrics house different bacteria

A study the University of Alberta found that surprisingly, the bacteria counts on synthetic versus natural fabrics were not significantly different. As long as there's moisture and air, bacteria will continue to multiply until they reach a saturation point.

There are some exceptions though, such as with Viscose, which is made from regenerated wood cellulose. Also, fabrics can be treated and infused with specific antimicrobials, such as copper, silver, or gold particles, to kill and prevent bacterial growth.

But more importantly, there's a big difference in the TYPES of bacteria that tend to grow in different fabrics.

Micrococcus grows the most on polyester because they're an aerobic bacteria that prefers the open-air lattice structure of synthetic fibers. The result is what causes your polyesters to stink more than cotton, especially when reworn, as micrococcus is known for its ability to create malodor from sweat secretions.

Meanwhile, a study at the University of Ghent in Belgium found that cotton tends to have the highest growth of Staphylococcus hominis, which is mostly harmless and usually found on the skin, but can occasionally cause infections under certain conditions. Nylons housed more propionibacterium, which are known to cause an intense, acidic foot odor.

So in short, it's probably worse to re-wear your high-quality synthetic workout clothes, mainly because of the stench. Cotton is better to re-wear, but be careful if you're sick or immunocompromised. If you must re-wear something the next day, leave your clothes somewhere to dry quickly, as opposed to throwing them in a damp hamper.

Not all workouts are created equal

Sweat is one of the biggest factors, as it provides the warm, damp environment that allows bacteria to thrive. For that reason, it might be OK to re-wear your workout clothes after less intense activities where you don't sweat as much, such as yoga or power walking, as opposed to a spin class or a CrossFit session.

Another thing to note is WHERE you wear your clothes to, because your clothes will pick up bacteria from your environment as well. Even if you don't sweat that much at the gym, your clothes will be picking up bacteria from other peoples' sweat left on gym mats and equipment.

Can you actually get an infection?

Infections aren't common, but they can occur. Anytime you wear tight, wet clothing for too long, especially when you put on yesterday's not-completely-dry yoga pants, it causes moisture to be trapped and retained, which can lead to fungal or yeast infections.

The risk of infections is also higher when your immune system is compromised, if you have any open wounds or sores, or if you're on certain meds like acne medication.

Speaking of which, another issue to look out for is acne. Re-wearing sweaty, dirty clothes can cause dirt and acne-causing bacteria to accumulate in your pores.