A small thought to help you sleep when you next get your head down - a study shows the average pillow is home to a host of potentially-harmful fungi.
Is counting sheep or counting fungi the best way to combat insomnia?
A University of Manchester team found up to 16 types of fungi in pillows they analysed, the Allergy journal reported.
Researchers said feather pillows had fewer species than synthetic versions, particularly in the case of a fungus which exacerbates asthma.
Experts advise disinfecting pillows but say fungi occur in most environments.
The researchers took samples from 10 pillows - five feather and five synthetic - which had been used for between 18 months and 20 years.
The fungal spores found in the pillows fed off human skins scales and dust mite faeces.
Fungal contamination of bedding was first uncovered by studies carried out in the 1930s, but few studies have been done since then.
Researchers found that all 10 pillows had a "substantial fungal load" with between four to 16 different species being identified on each, Allergy reported on its website.
The microscopic fungus Aspergillus fumigatus was particularly evident in synthetic pillows.
This fungus commonly invades the lungs and sinuses and can worsen asthma. It is also known to cause infection in leukaemia and bone marrow transplant patients.
The team also found pillows which contained fungi as diverse as bread and vine moulds. Some also had fungi which would usually be found on damp walls.
Lead researcher Professor Ashley Woodcock said the findings showed there was a "miniature ecosystem" operating inside pillows.
He added: "Since people spend a third of their life sleeping and breathing close to a potentially large and varied source of fungi, these findings certainly have important implications for patients with respiratory disease - especially asthma and sinusitis."
Dr Geoffrey Scott, chairman of the Fungal Research Trust, which funded the study, said the findings were interesting.
"I think particularly for asthma patients this is relevant. These fungi are found in the environment, so we are exposed to them everywhere.
"But I think it is still advisable to disinfect pillows and buy feather ones to help reduce the exposure in the home."
A spokesperson for the charity Asthma UK said: "We are aware that patients at the severe end of the spectrum of asthma are more likely to be hypersensitive to fungi than others with asthma.
"If you think that fungi could be a trigger for you, you should consult your GP or asthma nurse for advice."