How Bad Is It to Re-Wear Sweaty Workout Clothes?

You’re rushing to make sure you get your daily workout in and suddenly realize you have no more clean sports bras. Uh oh. What’s a person to do? Dig through the laundry basket and find one, of course. Most people have probably done this at one point or another whether for a sports bra, leggings, shorts, socks, or a T-shirt, but just how bad is this dirty little secret?

It really depends on how much you sweat, your infection risk, the type of garment, and how dirty the item is, says Deanne Mraz Robinson, MD, president and cofounder of Modern Dermatology in Westport, Connecticut. “Dirty, sweaty gym clothing is a breeding ground for pathogens such as bacteria and viruses, and their use can increase risks for superficial skin infections,” says Dr. Robinson, who is also an assistant clinical professor of dermatology at Yale University of Medicine in New Haven. On a grossness scale of 1 to 10, she gives this habit a solid 8.

Here are a few things our experts want you to keep in mind before you reuse your sweaty gym clothing.

You may smell

Bacteria, sweat, and body oils build up inside synthetic fabrics like your pre-worn sports bra and can cause a funky odour. “This is the immediate problem,” says Philip Tierno, PhD, a microbiologist and pathologist at New York University Grossman School of Medicine in New York City and author of The Secret Life of Germs. The more bacteria in your sweat, the greater the chances that you will stink.

(Related: Natural Deodorant Reviews—Which Ones Pass Our Sweat Test?)

You may develop a bacterial infection

You have germs all over your skin, but they are your germs and not necessarily disease-causing. (And in fact, in some cases are beneficial.) These bugs feast on your sweat, especially in humidity, and can multiply, Tierno explains. This likely won’t cause an infection without a break or tear in your skin. “As long as your skin is intact, there is a low risk of infection,” Tierno says. “But if you develop a rash and itch or scratch it, you can introduce a small lesion or abrasion and develop an infection.”

This can be dangerous if Staphylococcus aureus (staph) is one of the resident types of bacteria on your skin, as it can lead to infections, including one type, methicillin-resistant Staphylococcus aureus (MRSA). MRSA is an antibiotic-resistant germ that the World Health Organization and other health agencies are concerned about.

So, what happens if you get sweating in yesterday’s workout wear? Used items may be mixed with other germy clothing from family members, introducing organisms that aren’t typically part of your skin’s bacterial footprint, Tierno says. The possible result: a bacterial infection.

Your skin may break out

Re-wearing dirty gym clothes could increase your risk of an acne outbreak. Your pores can get clogged with sweat and dead skin cells, which could possibly trigger a breakout, says Michele S. Green, MD, a dermatologist at Lenox Hill Hospital in New York City. “When you sweat, your pores open up, which makes you susceptible to bacteria that can cause breakouts,” she says.

(Related: How Do I Deal With Body Acne?)

You may develop a yeast infection

Yeast lives on our skin, especially in the groin, under the breasts, and in other areas with skin folds. It also thrives in moist, warm, humid environments—you know, like the sweaty clothing sitting on your bathroom floor. Re-wearing sweaty clothes can cause your skin to become irritated from exposure to yeast and bacteria within clothing, says Dr. Green.

While you can get away with wearing certain workout items more than once, always wash your underwear and leggings—especially if you don’t wear underwear—after each use to lower the risk of vaginal yeast or bacterial infections. There’s more friction in that area when you’re exercising, which increases the risk of depositing bacteria or yeast deeper into the skin.

You may develop inflamed hair follicles

Heat and humidity, coupled with clothing that doesn’t breathe and is laden with bacteria, is a recipe for disaster. “During a workout, your skin comes in contact constantly with fabric or skin,” Dr. Green says. “When you re-wear sweaty clothes, any bacteria or dirt from your clothes can transfer onto your skin and trigger an inflammatory response.”

Folliculitis happens when hair follicles become inflamed. It’s one of the skin conditions that can look like acne: small red bumps or whiteheads in areas where you have hair follicles. Folliculitis can be itchy and sore, though mild cases heal within a few days.

Is it too germy to wear?

Dr. Robinson’s rule of thumb is simple: “Once saturated with sweat and visually soiled, it’s too dirty.” You can get away with re-wearing an item for several days, but not for long periods of time, Tierno adds. Never re-wear underwear or leggings, shorts, or pants that you wore when going commando.

Material may also make a difference. In one study, 26 people took an indoor cycling class wearing shirts made of cotton, polyester, or blends. A sniff test by a trained odor panel found polyester T-shirts smelled worse than cotton ones, according to the study in Applied and Environmental Microbiology. If you have to re-wear workout gear, hang it and let it air dry in a non-humid place between uses. “Bacteria can’t prosper without water,” Tierno says.

The last word

Re-wearing exercise clothing is risky. You may stink, break out, or develop yeast or bacterial infections. The risk depends on which item you re-use and the amount of wear. It’s okay to do once in a while, but if you are prone to staph infections, the risks likely outweigh any benefits.

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