PHD student Max Kelly, 24 and marine microbiologist Professor J Grant Burgess both from Newcastle University check clothing in a washing machine at the Benton Proctor and Gamble site in Newcastle, during research into the release of microfibres using different washing cycles. (Photo by Owen Humphreys/PA Images via Getty Images)
Video: Doing your laundry spills plastics into the ocean
03:54 - Source: CNN Style

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The number of times it’s appropriate to wear clothing items without washing them often seems based more on folklore or a person’s upbringing than professional advice.

TikTok user Allison Delperdang started a heated online debate when she posted a video January 10 saying she wears the same pajamas multiple times.

“When I was younger my parents always made us wear pajamas … multiple nights in a row because they weren’t dirty, and I still do that as an adult,” she said. “I need to know if, like, as adults we’re still doing that, or should I be literally making dirty clothes every single night?”

The answer — for pajamas as well as other clothes — technically depends on personal aspects such as sweat level and lifestyle, though for many people other, more abstract factors may come into play, experts say.

Our beliefs about clothing hygiene are largely “societal and cultural,” said Dr. Anthony Rossi, an assistant attending dermatologist at Memorial Sloan Kettering Cancer Center in New York City and a fellow of the American Academy of Dermatology. “People tend to over wash and ‘over hygiene’ themselves, because especially in America, we have a luxury of being able to do all that stuff all the time.”

Rewearing the same clothes — particularly on consecutive days — is “linked to avoiding decision fatigue, hence wearing the same clothes involves less decisions to make and less stress every morning,” said Manal Mohammed, senior lecturer of medical microbiology at the University of Westminster in London.

Not knowing when to wash your clothes can have consequences on both ends of the spectrum. Washing them too seldom could lead to skin problems or infections, and washing them too often could harm your clothing. The latter can also result in unnecessary laundry and use of resources.

Here are some guiding principles to help you determine when a garment can be worn again without washing and when it’s time to toss it in the hamper.

PHD student Max Kelly, 24 and marine microbiologist Professor J Grant Burgess both from Newcastle University check clothing in a washing machine at the Benton Proctor and Gamble site in Newcastle, during research into the release of microfibres using different washing cycles. (Photo by Owen Humphreys/PA Images via Getty Images)
Video: Doing your laundry spills plastics into the ocean
03:54 - Source: CNN Style

The universal rule: What you must wash

There’s no hard and fast rule for how many times you can wear clothing again, but experts say there are a few types that should be washed after every use: underwear, socks, tights, leggings and activewear. This advice also applies to any other clothes with stains, sweat, odor or visible dirt, Mohammed said.

These kinds of clothes are “on a part of our body that just has a lot of natural bacteria that lives on our body, like our microbiome, (yeast) and bacteria,” Rossi said. “Then from day-to-day activities, we sweat. That just breeds moisture and an environment where this bacteria can overgrow.”

Bacteria overgrowth can lead to infections, fungus and other skin issues, he added.