House dust mite project aims to reduce asthma

A promising new way of controlling the mites that can cause asthma and other allergies is now under development.

It could lead to dramatic progress in preventing these conditions and reduce the estimated £700 million a year spent in the UK on treating them.

The technique uses a computer model to assess how modifying a domestic environment can reduce numbers of house dust mites in beds, carpets and elsewhere.

Development of the model has been led by University College London (UCL), in collaboration with Cambridge University and other partners, and with funding from the Engineering and Physical Sciences Research Council (EPSRC). A 2 year follow-up project, also funded by EPSRC, will now improve the model and test it in homes around the UK.

Although almost invisible to the naked eye, house dust mites play a major role in asthma and other allergic conditions. The original EPSRC funded project found that mite numbers are heavily influenced by environmental conditions in homes, and by the heating regime, ventilation and humidity in particular. It produced a prototype model – the most advanced of its kind – that can assess how different building features and patterns of occupant use affect these conditions, and therefore house dust mite numbers. Room conditions are important because dust mites have a unique mechanism for taking up water which involves dribbling a salt solution from under their armpits to their mouth. This mechanism enables mites to take up water from the room air. If the room conditions become dry this salt solution crystallises, the mechanism stops and hence the mites dehydrate and eventually die.

The new project represents the next step in developing the model for use in devising anti-mite strategies for a range of UK house types. It will include laboratory monitoring of mite population growth in a range of conditions, which will generate data essential to the effectiveness of the model.

To validate the model, the project will also include a field study involving 60 houses across the country. This will measure temperature and humidity in bedrooms and beds, and monitor mite populations found in the beds.

Harnessing building science and acarology (the study of mites and ticks), the initiative is being led by Professor Tadj Oreszczyn of UCL. He said, “we aim to identify how homes can be designed and used so that mite populations are reduced to below the threshold at which health problems occur”.