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Dr Colin Michie

 

Should you get rid of those house dust mites?


Folk suffering from allergic problems inevitably try to find and remove anything in their surroundings which appear to make their condition worse. House dust mites have become a popular target. There are great temptations to invest in a new vacuum cleaner, flooring and bedding in an attempt to remove house dust mites from homes. But how useful are such measures? This subject is worth careful consideration before spending substantial sums of money and effort.

Our world teems with small creatures thriving on tiny particles of organic matter. Not only plants and fungi, but small insects and mites exist in their thousands within our homes. Most are barely visible, and usually cause us no concern. In temperate homes with the advent of central heating, increased humidity, together with vast food traps in the fabric of carpets, these organisms tend to multiply rapidly. They have no predators, and so little to limit their numbers. One mite, the house-dust mite (Dermatophagoides pteronyssinus or HDM) has been shown to be a source of allergens which can cause eczema, asthma and rhinitis. This mite lives off human skin particles and is particularly common in bedding, upholstered furniture and carpets. Some of the proteins in the excrement of these creatures can lead to a range of allergic reactions in susceptible humans.

So should we all get rid of HDM? This question is difficult. In order to reduce allergies in the average home it may be important to remove sources of smoke, nitrogen dioxide (from gas flames), damp (which encourages moulds) furry pets and larger insects such as cockroaches. Obvious sources of pollen may have to be restricted in some way. These measures will require the removal of old carpets and textiles and the provision of good ventilation, perhaps with a filter. It will also require regular cleaning of the home - never a popular topic!

So how does one specifically get rid of HDM? Ideally cleaning should remove all mite particles and not only living mites. An initial extensive steam cleaning of carpets and furnishings is recommended, together with freezing then washing of soft toys. Several treatments reduce further exposures to allergenic HDM particles at least ten-fold. Chemical acaricides, air filters, or a combination of regular bedroom laundry with specific bedding covers are effective. Regular vacuum cleaning and dusting will be needed, as well as special attention to soft toys. At present there are no comparative clinical studies of vacuum cleaners or bedding products; consumer magazines may guide you to find those products that have been formally tested.

Children with asthma, eczema or rhinitis or adults suffering from rhinitis will probably benefit from removing HDM. Sadly there are no clear large studies showing similar benefits to adults with asthma or eczema.

Surely treating HDM should help everyone with an allergy? Several reasons may explain why this is not the case. Firstly many with allergic conditions are sensitive to many allergens. Secondly many suffer deterioration in their conditions because of factors other than allergens. For instance stress and nutrition can have dramatic effects on all allergies, particularly those which have been established for some time. Thirdly, as the underlying problem is allergy, the sufferer may remove one allergen, only to react to another because the underlying cause remains unchanged and untreated. Removal of HDM for instance may be followed by an increased allergy to moulds.

Removing house dust mites may be of value, but please discuss the problem first with your medical advisors. Perhaps a formal consultation and possibly a skin test would help you decide whether to invest in mite eradication.

Useful sources of further information:

National Asthma Helpline 0845 701 0203

National Asthma Campaign 0207 226 2260 Website: http://www.asthma.org.uk

Consumer Association website: http://www.which.net

Information sites relating to the relevance of House Dust Mites: http://www.jr2.ox.ac.uk/bandolier/band41/b41-4.html http://www.niaid.nih.gov/publications/allergens/title.htm