How often should you wash your bed sheets?

Has it been weeks since you changed your bed sheets and pillowcases? If so, researchers say you may be sleeping with a “legion of germs.”

Mattress and bedding company Amerisleep swabbed three volunteers’ unwashed sheets and pillowcases at the start of each week for a month.

It found that after only one week, as many as 5 million colonies of bacteria can accumulate on a square inch of a bed sheet (more than 17,000 times the amount of bacteria on a toilet seat after one week), and 3 million can pile up on a square inch of a pillowcase (nearly 25,000 times more than the bacteria on a bathroom door knob).

After four weeks, as many as 11 million colonies of bacteria were found on a square inch of the sheets and pillowcases.

“Clean sheets and pillowcases at least weekly,” Amerisleep says. “Consider a more frequent cleaning schedule if you’re apt to fall asleep in a full face of makeup or after a sweat at the gym.”

The company also advises: “If you spend your day working somewhere with a lot of germs, consider taking a shower before bed. Not only will showers help clean you up and maintain a clean bed, but it can also be an excellent way to relax before bed. A warm shower as part of your bedtime routine can signal to your body it’s time for sleep.”