We hate to break it to you, but your bed sheets should really be washed once a week, according to a scientist who spoke with Business Insider.

The longer you skip laundry duty, the more your bed will start to resemble a "botanical park" of bacteria, says New York University microbiologist Philip Tierno. Your pillows can carry up to 16 different types of fungus—and that's not even counting the ones that hang out between your sheets.

Of course, sharing your bed with microscopic life sounds terrifying for a number of reasons, not the least of which is that it increases your risk of getting sick. Over time, bacteria from human sources like sweat and spit—and a few grosser ones that don't need to be mentioned—join forces with those from foreign bodies such as pollen, lint, and dust mites. When you're surrounded by these bacteria (like, say, during the third of your life that you spend snuggled in your sheets), they can trigger an allergic reaction and symptoms such as sniffling and sneezing—even if you don't usually suffer from allergies.

"If you touched dog poo in the street, you'd want to wash your hands," Tierno told Business Insider. "Consider that analogous to your bedding. If you saw what was there—but of course you don't see it—after a while you have to say to yourself, 'Do I want to sleep in that?'"

Now that you're going to be washing your sheets more regularly, be sure to read up on our guide to how often you should wash other household items and garments, from dish towels to jeans. You may want to stock up on laundry detergent beforehand.

[h/t IFL Science]