The average pair of clean underwear still contains about 0.1 grams of feces and could hold up to 10 grams, according to a Journal of Infection study led by Charles Gerba, PhD, microbiology professor at the University of Arizona. (Could the fact that this surprisingly high percentage of people don’t wash their underwear be to blame?)
If you aren’t already doing your laundry in hot water, it might be time to start. Anything below a hot cycle of 140 degree Fahrenheit won’t do much against bacteria, says Dr. Gerba. Cold water is “designed to get clothing clean but not eliminate microorganisms,” he says. Using an activated oxygen bleach detergent like OxiClean or Clorox 2 can sanitize your clothes, even if you don’t want to throw your delicates in hot water, says Dr. Gerba. (Don’t miss these other 7 tricks for washing clothes without ruining them.)
Without hot water and bleach, bacteria from your underwear can spread to other clothes in the wash too. Unloading that “clean” laundry into the dryer gets bacteria on your hands, which means you could spread it to other fabrics or even up your risk of infection by spreading the bacteria to everything you touch. Keep your underwear separate from the rest of your laundry to avoid spreading the germs, suggests Dr. Gerba. (Find out how often you should be washing your towels—most people don’t clean them enough.)
Even those best practices might not get rid of bacteria completely, though, because those germs don’t just disappear after your clothes have been in the laundry. (Learn how to tell if you use too much laundry detergent.) Some of that bacteria—including E. coli—stick around in the machine after the cycle is over, says Dr. Gerba. Washing your underwear last will keep that away from your other loads, but you should clean the machine itself by running an empty cycle after every underwear load. “Give the washing machine a mouth wash by running bleach through it and killing bacteria left,” he says.
Don’t miss these other 9 mind-blowing facts that will change the way you think about laundry.