'Since patients spend a third of their life sleeping and breathing close to a potentially large and varied source of fungi, these findings have important implications for patients with respiratory disease -- especially asthma and sinusitis.'

Researchers found up to 16 species of fungi, linked to everything from bread to shower mould, living in people's pillows. The fungi feed on the feces of the common house mite, which also lives in the pillow, and human skin cells, surviving in their own miniature ecosystem.

The most common microscopic fungus, Aspergillus fumigatus, can exacerbate asthma and is the leading cause of death in leukemia and bone marrow transplant patients.

Doctors advise those at risk to disinfect pillows regularly, but for most of us the microsystems under our noses are an inescapable part of a comfortable night's sleep.

Substantial Fungal Load

Fungal contamination of bedding has not been studied since 1936, so the Fungal Research Trust funded a team at Manchester University to look again at the bugs in our beds.

The team studied samples from ten pillows with between 1.5 and 20 years of regular use. Each pillow was found to contain a substantial fungal load. Surprisingly, Aspergillus fumigatus was particularly evident in synthetic pillows, along with other diverse types of fungi.

Professor Ashley Woodcock, who led the study, said there was a whole world living in our pillows: "We know that pillows are inhabited by the house dust mite, which eats fungi, and one theory is that the fungi are in turn using the house dust mites' feces as a major source of nitrogen and nutrition [along with human skin cells].

"There could therefore be a miniature ecosystem at work inside our pillows."

Asthma and Sinusitis

Aspergillus is a common fungus carried in the air as well as being found in cellars, household plant pots, compost, computers and ground pepper and spices, and is harmless to most of us. However, constant exposure to fungus in bed could be problematic, especially for those who already have respiratory problems such as asthma and allergic sinusitis.

Those who already have a weak immune system -- such as transplantation, AIDS and steroid treatment patients -- are also in danger.

Aspergillus is difficult to treat and as many as one in 25 patients who die in modern European teaching hospitals are infected.

Hospital pillows have plastic covers and so are unlikely to cause problems, but patients being discharged to their homes -- where pillows may be old and fungus-ridden -- could be at real risk of infection.

Professor Woodcock added: "Since patients spend a third of their life sleeping and breathing close to a potentially large and varied source of fungi, these findings have important implications for patients with respiratory disease -- especially asthma and sinusitis."

Dr. Geoffrey Scott, chairman of the Fungal Research Trust, said that there could be benefit from disinfecting pillows regularly.

"These findings are of major significance to people with allergic lung diseases and damaged immune systems -- especially those sent home from hospital," he said.