Your dirty underwear is contaminating your fresh laundry

Are dirty undies undoing your fresh laundry? New research suggests tiny bits of fecal matter from your dirty underwear can linger through the wash and contaminate your fresh laundry.

TORONTO — Fecal matter from your dirty underwear is probably still lurking in your fresh laundry, according to multiple studies. Even worse, one microbiologist has found that bacteria such as E.coli can survive the average laundry cycle.

But despite the ick factor not all experts are worried, noting that exposure to bacteria makes our immune systems stronger.

“The average adult undergarment has about a tenth of a gram of fecal matter,” Dr. Charles Gerba, renowned germ researcher and professor of microbiology at the University of Arizona, told CTVNews.ca by telephone earlier this month.

“By my estimations, a week’s worth of dirty underwearwould amount to about an airline peanut-sized amount of fecal matter.”

Gerba, an environmental microbiologist best known for his research in water quality, turned his attention to household laundry a decade ago thanks to a rise in energy-saving cold-water washing.

According to his research, Gerba says dirty underwear and jeans are among the worst offenders for collecting bacteria when it comes to our clothes.

But hand towels remain the number one culprit for containing fecal bacteria, with over 80 per cent testing positive.

“They are thick, they stay moist, and allow bacteria to grow,” he said. “You would get more fecal bacteria from wiping your face on a towel than you would sticking your head in the toilet, from what we’ve gathered.”

More concerning, Gerba says his research shows that bacteria such as E.coli, and Staphylococcus aureus (MRSA) largely survive the average laundry cycle.

“When I was a kid it was always hot water and harsh detergents, but nowadays its cold water and mild detergents,” said Gerba, who added that top-loading washing machines that often leave behind a thin layer of water may be contributing to the spread of germs.

“If you do a load of underwear and then you do a load of handkerchiefs then you are blowing your nose with your dirty underwear, essentially.”

Another study found that 40 per cent of sterile cloths washed in non-bleach laundry detergent contained fecal bacteria -- with enough left over to contaminate the next load.

Is there any real risk?

Gerba admits that it’s hard to document cases where individuals have become ill from bacteria found in their washing machines, but notes that there have been several documented cases in hospitals and nursing homes.

“Although rare, serious outbreaks have been associated with the transmission of microorganisms associated with inappropriate management of hospital linens… and recently reported fungal outbreaks have resulted in severe infection and death in immune-compromised patients,” reads a 2018 briefing from Public Health Ontario.

But Dr. Laura Sycuro, assistant professor at the University of Calgary’s Department of Microbiology, Immunology & Infectious Diseases, says the average, healthy Canadian has no reason to be concerned.

“We live in a microbial world. Everything we come into contact has [bacteria],” Sycuro told CTVNews.ca by telephone from Calgary.

“As microbiologists, we don’t really have much concern about this when we are healthy and our immune systems are intact. We know now that when you’re exposed to bacteria early in life it can help your immune system not to be too sensitive.”

In fact, Sycuro makes the argument that being exposed to more bacteria reduces the risk of developing allergies or intolerances -- especially for young children.

“The average person has E.coli in their body and in their gut and it causes no harm,” she said, noting that when we go on vacation, the water we swim in has 10,000 times more bacteria than in our washing machines.

“Certainly if you are severely immune compromised you might be more sensitive… [but] I don’t think you have to change your laundering practices because you are raising a family.”

How to combat washing machine bacteria

If you happen to be a bit of a germophobe, Gerba suggests doing a rinse of hot water and bleach through your washing machine once a week (especially after washing your dirty underwear).

If you don’t like using bleach, a bleach alternative will also do the trick.

Most importantly, Gerba recommends washing your hands thoroughly after sorting laundry to prevent the spread of germs.