Your bedsheets could become a "botanical park" of bacteria and fungus if you do not change them often enough.
It becomes even more crucial to change them during hot weather, which the UK has been experiencing lately.
A clinical professor in Microbiology told Business Insider that we should aim to wash our bed sheets once a week.
Philip M. Tierno says our beds can quickly become a "botanical park" of bacteria and fungus.
What this really means is you're sharing a bed with fungi and bacteria from your sweat, sputum, skin cells and vaginal and anal excretions.
On top of this are foreign microbes like animal dander, pollen, soil, lint, dust mite debris and faeces.
The microbiologist says that the build-up of bacteria can become "significant" in as little as a week, which is why he recommends weekly wash-days.
Having unclean bedding is harmful because your mouth and nose are so close to the sheets, you're forced to breathe in those spores.
"Even if you don't have allergies per se, you can have an allergic response," Tierno explains.
One or two weeks is enough to leave anyone with a scratchy throat, but particularly those suffering from respiratory conditions like asthma.
Why is it more important to wash bedding in hot weather?
We produce approximately 26 gallons of sweat in bed every year and, when it's hot and humid outside, this moist environment becomes an "ideal fungal culture medium", according to scientists.
That basically means it's the perfect condition for fungus and bacteria to spread on your lovely sheets.
So when it's warm outside it's even more important to stick to weekly washing.
Better get that duvet cover in the washing machine, stat.