There are some pieces of clothing you can get away with wearing multiple days in a row, but underpants aren't one of them. Most of us don't feel comfortable putting on a pair of underwear until it has gone through a vigorous, soapy wash cycle. But according to experts, even that may not be enough to fully sanitize your most intimate garments.
The Good Housekeeping Institute reports that freshly laundered underwear still contains as many as 10,000 living bacteria. A study led by microbiologist Dr. Charles Gerba puts it in more colorful terms, claiming that the average pair of clean undies contains up to a 10th of a gram of feces.
The bacteria that cling to your underpants are the same microbes that thrive on the private areas of your skin no matter how well you wash them. This includes potentially harmful pathogens like E. coli. That bacteria build up over time, and it could potentially lead to health problems like urinary tract infections.
If you have a fairly new pair of undergarments, the minuscule amount of germs you can't wash out of them is nothing to worry about. But to keep your underwear drawer as sanitary as possible, throw away any items that you've been wearing for a year or more and replace them with fresh pairs.
With undergarments you're wearing regularly, you can reduce germ buildup by washing them in hot water (at least 140°F) with bleach. Letting them dry in the sun is another good way to kill bacteria. Here are more tips for cleaning the items you use most often.