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You may assume the washing machine is doing its job by getting your clothes clean, but your laundry may not be as fresh as you think — especially if you share your washing machine with a housemate.
Just one small speck of fecal matter contains millions of virus-causing bacteria. And no matter how diligent you are, there’s at least one tenth of a gram of fecal matter left behind on your underwear, says Chuck Gerba, a professor of Microbiology at the University of Arizona.
But there’s more to be concerned about — the bacteria from the fecal-stained underwear can spread in the washing machine and stay there until the next load of laundry. If a sick person is washing their clothes — or more specifically their underwear — it’s likely their sickness-causing organisms will find their way onto the next batch of clothes that enter the machine. This comes as particularly upsetting news for anyone who shares their washing machine with either a housemate or even an entire apartment building.
“We’ve found that one germy item in the washer will spread to 90 percent of the other items,” said Kelly Reynolds, a germ researcher and associate professor of Environmental Health at the University of Arizona. “When it comes to molds that cause skin or respiratory infections, or organisms that cause colds, flu and stomach flu, most of them will survive the wash cycle.”
Not even setting the water in the washing machine to ‘hot’ will help kill the bacteria completely.
However, there is a bit of good news that involves the next step in doing laundry — the dryer, which may be able to kill off most of those harmful microorganisms.
“High heat drying for at least 28 minutes is the most effective way to kill viruses,” Reynolds explains. ‘High heat’ is crucial, Reynolds says. Energy efficient, low-heat settings may not be as effective in killing unhealthy microorganisms.
For many people, sharing a washing machine with a housemate or neighbors in your apartment building is unavoidable. In those cases — especially if you know that someone is sick — run a wash cycle with bleach or another disinfectant to clean out the washing machine.
When transferring clothes between the washer and dryer, be sure to wash your hands after handling them because unless you’ve used bleach or another disinfectant, those wet clothing items are most likely not sanitized.
If you have some clothing items that should not go into the dryer, it’s also fine to air dry them outside or in direct sunlight. The ultraviolet rays from the sun have disinfecting properties, Reynolds says.
Danielle Tarasiuk is a multimedia journalist based in Los Angeles. Her work has been published on AllDay.com, Yahoo! Sports, KCET, and NPR-affiliate stations KPCC and KCRW. She’s a proud Sarah Lawrence College and USC Annenberg alumn.