Here’s What Happens If You Don’t Change Your Underwear

Updated: Sep. 11, 2023

One out of every two Americans goes multiple days on a single pair of undies. Do you? Here's how often you should change your underwear, and what happens when you don't.

close up of woman's underwear while on toilet in bathroomPeopleImages/Getty Images

Wearing clean underwear every day is one of the first rules of hygiene most of us were taught as children, along with brushing your teeth before bed and not kissing the dog on the lips. So why is it that in a recent survey of over 2,000 Americans, nearly half of adults confessed to wearing their undies for two days or (gulp) even longer? Not only did 45% of people surveyed by underwear company Tommy John say they don’t always change their underwear daily but 13 percent said they’d gone for a week or longer in the same pair. (No word on whether or not this involved turning them inside out.) Maybe they don’t know the reasons we wear underwear in the first place.

“I’ve definitely done at least three days in the same boxers; it’s easier, it’s less laundry and honestly I just forget,” says Kellen, a 21-year-old college student who declined to be further identified in case his mother is reading.

This may be a valid concern because he also admits to putting the same pair of dirty undies back on after showering. “I leave them scrunched up in my jeans so all I have to do is step back in and pull them up and I’m out!”

Okay, while there may be a case for convenience and perhaps even environmental friendliness, when it comes to your health wearing dirty underwear shouldn’t even be a consideration, says Marisa Garshick, MD, a board-certified dermatologist at MDCS Dermatology and clinical assistant professor of dermatology at New York Presbyterian-Cornell.

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The health risks of wearing the same underwear for days

“Dirty or used underwear provide a breeding ground for bacteria, yeast and fungi, and are often contaminated with fecal matter—that’s poo droppings,” says Sherry A. Ross, MD, an ob-gyn in Santa Monica, California and author of She-ology: The Definitive Guide to Women’s Intimate Health. The most obvious problem with sitting around in your own poop is the odor that can build up over time, and you may not even realize it as many people develop “nose blindness” to their own body odors, she says.

Acne is another concern, Dr. Garshick says. You knew you could get the unsightly red bumps on your face and even neck or back but did you know you can also get them on your rear end or other body parts? Wearing dirty underwear traps sweat, dirt and bacteria and holds them close to your skin. “When sweat or oil sits on the skin for too long, it can lead to bad odor or clogged pores, leading to breakouts,” she says.

You’re also at an increased risk for genital irritation and infections when wearing your underwear for extended periods of time, Dr. Ross says. “Will it kill you to wear dirty underwear? Probably not, but the longer you wear the same pair, the more your risks increase,” she says.

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How often should you change your underwear?

“In general, it is recommended to change your underwear daily to prevent the buildup of dirt, sweat, bacteria and oil,” Dr. Garshick says. However, there may be times you should change it even more frequently. Given the moist environment of your groin and buttocks, if you are particularly active or sweaty, be sure to change your underwear post-workout or if it feels sweaty or wet during the day, she says.

Other times you need to change undies stat: If your underwear are visibly stained with urine or feces, if you’re menstruating and blood has leaked through, or if you have any type of infection or open wound down under.

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What happens if you rewear the same pair of underwear?

Sometimes life happens. Maybe you missed laundry day or your underwear sprouted holes overnight and you haven’t had time to shop or you’re in a situation where it’s just not convenient to have a fresh pair handy. If it only happens every once in a while, don’t sweat it. “Occasionally forgetting to change your underwear for a few days is unlikely to cause significant damage,” Dr. Garshick says.

However, if you often find yourself in the position of needing to wear your underwear for multiple days in a row (looking at you, Kellen), it may be worth investing in higher-end undies designed to be more durable and lessen the risk of infection.

“We actually sponsored a guy hiking the Appalachian Trail and one of his requirements was that his underwear had to last multiple days in a row because he could only pack a very limited amount of clothing,” says Stacey Blume, an underwear technician and designer and founder of Noble Titan. She designed the brand’s performance underwear with this exact scenario in mind—heavy wear over multiple days.

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The key to re-wearing undies and not having issues is the fabric and fit, she says. She uses a poly-spandex fabric designed to wick away sweat and designed a waistband that functions as a sweatband, keeping sweat from dripping down and pooling in the underwear. (And as anyone who’s ever done a really sweaty workout knows, it’s is a real problem!)

The, ahem, bottom line: Make clean underwear a daily priority, dirty underwear isn’t worth the risk.

As for Kellen? “I’d like to say it’s never gonna happen again but we both know it’s totally gonna happen again,” he says. Kellen, your mom would like a word…

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