People With Asthma May Still Benefit from Getting Rid of Dust Mites

Sloane Miller Health Guide
  • Have you seen the reports circulating that say: "... the most widely recommended treatments to reduce dust mites had no effect on the symptoms of asthma sufferers, researchers in Denmark found."  MSNBC reported on this a few weeks back.


    That's alarming, as it seems to go against what we've always heard about dust mites: reduce them, their waste and their carcasses and you will greatly reduce your allergies and asthma.

  reported on the same study and had this to say: "We sent the study to a panel of experts, and their response was that the study might show that dust mite control could make a difference if it is used as part of a larger program, including using air conditioning and keeping your windows closed, washing your hair and clothes at night and keeping pets indoors. Wrapping your mattress could also be helpful, but if that is your only effort to control dust mites it won't make much difference."

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    That is a more balanced statement (i.e. irritant reduction is part of a larger overall program, no one element solves any problem), but still I wondered "what is going on here? " Where did the researchers get their information since it seems to go against commonly held beliefs?


    The Cochrane Collaboration Review

    I read another dust mite related "study," which was not a direct study but a review conducted by Gøtzsche PC, Johansen HK, Schmidt LM, Burr ML  of The Cochrane Collaboration. The mission of The Cochrane Collaboration: "Cochrane Reviews are based on the best available information about healthcare interventions. They explore the evidence for and against the effectiveness and appropriateness of treatments (medications, surgery, education, etc) in specific circumstances."


    This review  of 49 trials included a total of 2,733 patients from as far back as 1973. The review was first publishd in 2004 and republishd in 2007. This researchers conducting this review wrote, "We were unable to demonstrate any clinical benefit to mite-sensitive asthmatics of measures designed to reduce mite exposure."  


    However they also state that: "Adherence to the applied measures was rarely evaluated...[and] that mite reduction was determined in different ways in the various studies. Some recorded mite counts and some measured antigen levels, using dust samples from different sources, and the reductions reported do not necessarily correspond to a similar reduction in the patients' exposure. For example,removing mites from the surface of mattresses and pillows does not affect the mite content of blankets or duvets, and merely killing the mites does not necessarily reduce airborne mite antigen, if nothing is done to remove the fecal particles that contain it. A potential reservoir for mites is the scalp, and it has been suggested that neglect of this source may explain the failure of many trials of mite eradication."


    Three Weaknesses of the Review

    But this review came under some fire of its own. The Allergy and Asthma Foundation of America issued a statement repudiating several of the Cochrane's conclusions. After reading the report, I have to agree with AAFA's statements.


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    First the review includes studies from 35 years ago.  As AAFA says: "... environmental control techniques, tools and research have advanced over the past 35 years."


    Secondly, as AAFA states: "Many of the studies included in the Cochrane review are themselves antiquated, limited and potentially biased, each in its own way.  For example, it is well known that several approaches used in the past for reducing mites in homes were not effective, such as acaricidal agents, etc." FYI, acaricidal means it kills mites.


    Thirdly, the Cochrane review acknowledges that, "differing physical methods and protocols were employed in each of the several studies ... (i.e. different types/brands/materials of bedding covers and barriers, different care and washing instructions/methods, etc.) making Cochrane's combined "meta analysis" somewhat of an apples-to-oranges exercise."



    What To Do?

    The Cochrane report concludes: "Chemical and physical methods aimed at reducing exposure to house dust mite allergens cannot be recommended."


    Based on what I've read, I cannot agree because of the review's weaknesses as I've mentioned above.


    AAFA's conclusion is a balanced assessment: "... dust mite reduction is not easy and that mite reduction alone should not be considered the only method of allergen reduction in the home.  A multi-disciplinary approach to allergen and irritant reduction using scientifically validated tools and techniques must be employed, which may include vacuuming, bedding barriers, encasements, removal of pets, anti-smoking measures, mold remediation, rodent and insect removal, indoor pollen avoidance, air filtration and more."

Published On: May 14, 2008