Dust mites study 'debunks bed theory'

Most dust mites, which can trigger asthma symptoms, are not in your bed but in the rest of the house and outside it, says study.

Bed is not the major culprit for dust mites which can trigger asthma symptoms, says a small Australian study debunking the commonly-held view.

On average, about 10 per cent of total daily exposure occurred while sleeping in bed, while 50 per cent was elsewhere in the house and 40 per cent on transport, in offices and other buildings.

The Woolcock Institute of Medical Research study, involving 10 people tracked for 20 days, is published in the journal PLOS ONE.

Chief investigator Associate Professor Euan Tovey said thousands of Australians try to avoid allergens by sanitising their bedrooms and investing in low-allergy bedding and protector sheets.

"While such specialist bedding probably offers some protection, it's elsewhere in the house, plus in offices and on public transport - that you really need to protect yourself," he said.

"But, sadly, protecting yourself outside the bedroom poses all sorts of new challenges."

The researchers measured dust mite exposure continuously throughout the day and night using an Australian-built prototype sampler.

They said the clip-on device is the first to accurately measure the pattern of dust mite allergen exposure that people receive as they go through their day.

The results showed wide variations between people, but on average only about 10 per cent of the total daily exposure occurred while sleeping in bed.

"These figures debunk the 40-year old belief that the bed is the main site of allergen exposure," said Prof Tovey.

House dust mites are the world's most common allergy-causing protein, with up to 1.2 billion people displaying some allergy to mites.

Exposure can cause symptoms such as sneezing, asthma symptoms, and red and watery eyes.

"We have long realised that most dust in houses and in clothing contains mite allergen," he said.

"But what we had not sufficiently taken into account is that dust needs to be dispersed into the air by movement before it can be inhaled.

"Generally, you don't move much in your sleep and so exposure in beds is much less than we thought."