|
|
House dust mites -
Latest additions to our information
Main mite page: To return to the main mite control page click here.
|
|
British Medical Journal report suggests house dust mite control does not help asthma.
The British Medical Journal has just published a statistical analysis of objective trials of house dust mite control and concluded that there was no evidence of benefit to patients with asthma attributed to house dust mites. Before embarking on a lot of expense and trouble you will surely want to know what this report has to say and whether it should be regarded as reliable. Our main house dust mite page has a link to a new page on this, and to the web versions of the original articles.
|
|
Carpet-free bedrooms help. Mattress covers help. Anti-mite carpet shampoo does not.
A report from Melbourne, Australia, (Sporik and others, Journal of Allergy and Clinical Immunology, April 1998, vol. 101, pp451 -456) shows yet again that having a bedroom floor without carpet is associated with less house dust mite material on floors and that dust-proof bedding covers reduce mite dust from bedding, whilst shampooing carpets with a mite-killing material made no detectable difference.
Dust from uncarpeted floors had about one tenth of the mite material concentration found in carpeted floors when enough dust could be vacuumed up for analysis. But in many cases (24%) the uncarpeted floors did not yield enough dust for the test, so the true result is probably a much greater difference.
Beds with mattress covers yielded much lower mite material concentrations than uncovered mattresses. The mattress covers were made of Tyvek (DAC Allergy Covers, Allersearch), a nonwoven fabric made from high density polyethylene fibres. Such bedding covers are widely sold under a variety of brand names. We have previously considered them of unproven value, and these results show that they are effective and remain so for at least a year. Tyvek covers are popular because they are much cheaper than other types. The effectiveness of Tyvek was not compared with that of other materials. We are revising our advice on bedding covers because of these research results.
The differences remained over a one year period, showing no tendency to decrease with time. The differences were large enough to be expected to affect symptoms in children with asthma.
"Allerite®" carpet shampoo (Vax®) did not make any detectable difference to mite material concentrations, and did not seem to reduce the amount of dust significantly.
Comment:
Many others have shown that dust-proof bedcovers cause a great reduction in mite dust at the surface of the bed. It has also been found previously that there is a correlation between mite dust levels in bedroom carpet and in the beds. It seems that mites from carpets find their way into beds. Unfortunately this study did not seem to take the opportunity to check whether flooring affected mite dust in beds.
Many people have tried to show benefit from mite-killing sprays, carpet powders and carpet shampoos. All the substantial studies of which I am aware have failed to show that they cause a significant reduction in mite dust or an improvement in symptoms.
All over the world people continue to sell mite-killing materials, and people continue to buy and use them in preference to doing the two things known to help most; covering the bedding with appropriate coverings, and removing carpets. This may be because the unit price for the chemicals seems low compared to the cost of bed covers and reflooring. However the cost of using the chemicals regularly as generally advised by the manufacturers is usually surprisingly high over a period of some years.
Help!
If you spot mistakes or have questions, or have something useful or instructive to tell us about the topic on this page, please e-mail us. We cannot reply to all mail.
To return to the main mite control page click here.
This page is maintained by Martin Stern
It was rewritten 25 May 1998. BMJ article Oct 1998. Last update 18 Jan 2000.
Copyright © 1997 M. A. Stern
