Scientists say we spend more than a third of our lives in bed (some of us probs spend at least half but sure no pointing fingers eh?), so it makes sense that your sheets should be kept squeaky clean.
Business Insider report that our cosy beds can soon turn into a "botanical park" of bacteria and fungus, and that bacteria found in the sheets can even make us sick.
Humans naturally produce roughly 26 gallons of sweat in bed every year.
A recent study of pillows found that those that were 1 1/2 to 20 years old contained as many as 16 different species of fungus.
Add in sweat, skin cells, animal dander, pollen, dust mite debris and soil, and you've got a pretty filthy mix in there.
So, how often to change them?
According to New York University microbiologist Philip Tierno, we should be changing our sheets AT LEAST once a week.
How often do you change yours?