2014 British/ Scottish Asthma Guidelines

A question for Dr Mitchell - The recent 2014 British/ Scottish Asthma Guidelines recommend educators not to recommend Hepa Fliters and dustmite encasements/ Your comment please.

Thanks for that information.  I was not aware of that recommendation.  I am, however, aware of several high profile studies questioning the efficacy of HEPA air cleaners and also dust mite impermeable encasements.  These recommendations may be based on those results.  I will explore this further.

Those studies, incidentally, did not specifically tailor the use of dust mite covers to those that had dust mite allergy; and additionally, they were singe-factor studies, looking at just that component of risk.  Most children have many different risks - intervening on just one is not likely to be effective.  I will find out more about those guidelines and get back to you about this issue.

Best regards,





The anonymous person asked about HEPA filters, but the response from Dr. Mitchell referred to HEPA air cleaners.   So those are 2 different tools correct?  Filters go in a vacuum cleaner and air cleaners are its own tool.  Do I have this right?  Thanks. 

Thanks for these questions regarding air filtration, and the British/Scottish Guidelines.

First, Geri, you are correct, I assumed the initial question referred to HEPA air cleaners, which we recommended (and in some cases provided) in our studies for those who had pets and pet allergy, or had smokers in the home, and/or evidence of mold.  We also recommended (and in some cases provided) HEPA vacuums for all our participants.  These are indeed different tools, although they address the same issue - overall allergen exposures.  Incidentally, we have also used self-adhesive filters that can be cut to the size of a room vent and used to reduce allergen levels when patients do not have access to main furnace vents.  These approaches to lowering overall allergen load in the home seemed sensible and useful to our investigators although we did not study them in the absence of our fully tailored, multifaceted interventions.  So, to speak definitively about their effectiveness alone, is not possible. 

The British/Scottish Asthma 2014 Guideline recommendation against employing physical methods (i.e.., filters or bedding covers) to reduce dust mite levels in homes was somewhat surprising.  It appears to be based upon the Cochrane review which includes some disconfirming data from studies that I believe are inappropriate since they examined this single risk factor, namely, dust mite intervention via HEPA filtration or mite impermeable bed covers.  It was interesting reading these British guidelines; they are very sensitive to making recommendations unless the data are absolutely clear and consistent.  Our science and the quality of the many variety of research studies seldom provides such consistency and clarity.  The British/Scottish guidelines, however, do recognize the importance of  "tailoring" such recommendations.  In their guidelines, shortly after recommending against the use of filters for dust mites, they acknowledge their potential usefulness for pet allergen ("In homes where there is no cat but still detectable cat allergen, there may be a benefit from introducing additional avoidance measures such as air filters and high efficiency vacuum cleaners for cat allergic patients."  2014 British/Scottish asthma guidelines, page 52.)

Finally, (and I apologize for this long answer..) I was interested to note how sensitive these British guidelines are to the potential expense of non-medical interventions.  I wonder if structural differences in the U.S.. versus U.K.. situations might not account for some of the difference in emphasis within our guidelines.  In the U.K.. National Health System (NHS) medical care and medications may be considerably less expensive (or free) as compared to purchasing HEPA air cleaners or vacuums.  In the U.S.., the expense and difficulty of accessing health care and/or medications may make self management approaches relatively less costly.