Products and interventions to reduce the effect of household dust on asthma and allergies may be a waste of time and money, a new review suggests.

Some people with asthma are allergic to minute house dust mites and the allergens from these mites can trigger asthma attacks.

Strategies that have been used to try and target these mites include encasing mattresses and pillows in covers so that they cannot get through; frequent washing of bed linen in hot water; and using chemicals against them.

But researchers based at the Nordic Cochrane Centre in Copenhagen claim today that no chemical or physical intervention to reduce exposure to house dust mites is effective.

They reviewed 54 studies of 3,000 asthma patients.

Some of the studies achieved reductions of more than 50 per cent but the review says even reducing environmental allergens by 90 per cent is insufficient.

“We can conclude with confidence that there is no need to buy expensive vacuum cleaners or mattress covers or to use chemical methods against house dust mites, because these treatments do not work,” said lead author Dr Peter Gotzsche.

“If you are wondering why it is that mattress covers and the other strategies are not effective, the likely answer is that all these treatments do not have a large enough effect on the occurrence of allergens from house dust mites.

“The level of allergens is so high in most homes that what remains after the treatment is still high enough to cause asthma attacks.”

Commenting on the review, Dr Noreen Clark, professor of public health at the University of Michigan, said: “Patient treatment and counselling should focus on a few things that evidence shows will be significant in getting the disease under control.

“This study suggests that trying to reduce exposure to dust mites by covering mattresses, using ionizers, washing bedding at high temperatures, and so on, will not help and should not be on the list.”

Leanne Male, assistant research director at Asthma UK, added: “This updated review confirms previous evidence which suggests that dust mite prevention methods have little effect on reducing overall asthma symptoms.

“We believe however that measures such as washing bed linen at high temperatures and removing soft toys from beds can make life easier for the 90 per cent of people whose asthma is triggered by dust mites, and may enable them to manage their asthma with less medicine. This is also a view represented in clinical guidelines for asthma management.”