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Underwear

"Every pair of dirty underwear has traces of feces,” says Kelly Reynolds, PhD, environmental microbiologist at the University of Arizona—and that can mean E. coli and other bacteria are in there, too.

To kill germs and keep ’em from spreading to other clothes, wash your underwear separately from the rest of your laundry on the highest temperature possible, not in cold—many germs survive in cold water, Reynolds says. Dry until the load is fully dry; wet or damp laundry provides a perfect environment for bacteria growth.

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