We spend more than a third of our lives in bed - but that place can quickly blossom into a "botanical park" of bacteria and fungus1, according to New York University microbiologist Philip Tierno.
If left for too long, the microscopic2
life within the wrinkles and folds of our bed sheets can even make us sick, Tierno told Business Insider.
To stem the invisible tide, he said sheets should be washed once a week.
Humans naturally produce roughly 26 gallons of sweat in bed every year. When it's hot and humid outside, this moisture becomes what scientists call an "ideal fungal culture medium."
In a recent study that assessed the level of fungal contamination in bedding, researchers found that feather and synthetic3
pillows between 1.5 and 20 years old can contain between four and 17 different species of fungus.
And it's not just your own microbial life you're sleeping with. In addition to the fungi4
and bacteria that come from your sweat, sputum, skin cells, and vaginal and anal excretions, you also share your bed with foreign microbes.
These include animal dander, pollen5
, soil, lint6
, dust mite7 debris8
and faeces, and finishing agents from whatever your sheets are made from, to name a few.
Tierno says all that gunk becomes "significant" in as little as a week. And unclean bedding still exposes you to materials that can trigger the sniffing9
and sneezing, since the microbes are so close to your mouth and nose that you're almost forced to breathe them in.