Imagine your pillow or mattress came with a health warning: ‘Contains bacteria, fungi and mites linked to poor sleep.’
It sounds extreme but scientists say our bedding absorbs our sweat and the flakes of skin we shed every night, creating a rich food supply for the ‘bed biome’ – the community of microbes and mites that share our bed. What’s more, this could affect our sleep quality.
‘The human skin is home to millions of bacteria and fungi, and each night we transfer these onto our sheets and pillows,’ says Primrose Freestone, an associate professor in clinical microbiology at Leicester University. ‘This creates the perfect diet for invisible mites that live deep in our bedding, pillows and mattresses.’
The more these mites eat and reproduce, the more droppings accumulate in your bed, she says, which can trigger a runny or blocked nose, asthma, eczema and other allergic reactions.
A main concern is that these particles are breathed in during the night. The body releases histamine as part of the immune response to them – this makes the lining of the nose swell, leaving many people struggling to breathe properly as they sleep. Forced to breathe through their mouths, they then snore.
A 2017 study of people with dust mite allergy found around 70 per cent also had problems such as poor sleep quality, snoring and waking during the night, reported the journal Allergy, Asthma & Clinical Immunology.
And it’s not just mites. ‘We think the combination of sweat, heat at night when lying on the pillow, skin scales and house dust mite droppings provide a great environment for fungi to grow,’ says David Denning, a retired professor of infectious diseases.
He says tests on old pillows found up to 2.1 million live fungal spores per gram of pillow.
Scientists say our bedding absorbs our sweat and the flakes of skin we shed every night, creating a rich food supply for the ‘bed biome’
A 2005 study in the journal Science found that one of these was Aspergillus fumigatus, a fungus that can cause allergic reactions and asthma attacks. The researchers recommended replacing pillows every year.
Chuck Gerba, a professor of environmental microbiology at the University of Arizona, US, also advises people not to sleep with wet hair, as moisture on the pillow can encourage mould and helps mites and fungi flourish.
Scalp fungal infections or facial breakouts are linked to sleeping with wet hair.
‘And think before letting pets sleep on your bed – they can carry a range of pathogenic bacteria and parasites which can cause serious illness in humans,’ adds Professor Freestone.
These include Campylobacter and Salmonella bacteria which cause diarrhoea and stomach infections. A study in BMC Infectious Diseases suggested Campylobacter can survive for six days and some types of Salmonella up to four years on bedding. Staphylococcus aureus, which causes skin infections, can survive for over a month.
Other bacteria linked to stomach infections, including E. coli and Enterococcus, can persist on bedding for several weeks.
Dust mites die within roughly six to 11 days when the air is dry or there is low humidity, as they dehydrate – but in damp conditions can persist for months. Fungal spores can also survive on bedding for months.
‘The simplest way to get a good night’s sleep is to remove the bed biome, by thoroughly and frequently washing the bedding,’ says Professor Freestone. ‘The NHS advises changing and washing bed sheets and pillow cases every week – and more often (every three to four days) if the bed occupant has an infection or sweats a lot,’ she says.
Researchers advise people not to sleep with wet hair, as moisture on the pillow can encourage mould
‘If your pets sleep on your bed, wash the bedding at least every three days. And set the machine at a minimum of 60c to kill the bed mites, bacteria and fungi.’
A 2022 YouGov poll found a third of Britons change their sheets just fortnightly and one in five only monthly. Younger people and men were least likely to wash sheets regularly.
Professor Freestone also recommends washing pillows every four to six months, vacuuming mattresses weekly and using a steam iron on your sheets and pillowcases to kill any bacteria, fungi or mites – and their eggs – after washing.
Items that can’t be washed at 60c, such as pillows, should be ‘put in the freezer for at least eight hours’, she adds, as the cold will kill anything lurking in them.
‘And leaving the duvet pulled back during the day gives the mattress time to dry out, reducing the conditions mites prefer.’
But Professor Mike Oreszczyn, an indoor environment specialist at University College London, notes that cleaning won’t be enough in a damp building.
‘Dust mites thrive in moist environments,’ he says. He recommends opening windows daily, using dehumidifiers and heating the whole house to reduce humidity.