House dust mite avoidance measures for perennial allergic rhinitis.

BACKGROUND: In developed countries, it is estimated that approximately 30% of the general population suffer from one or more allergic disorders, of which allergic rhinitis is the most common. Perennial rhinitis is most often due to allergy to the house dust mite. In such patients, house dust mite avoidance is logical, but there is considerable uncertainty regarding the efficacy and effectiveness of interventions designed to reduce dust mite exposure.

OBJECTIVES: To assess the benefit (and harm) of measures designed to reduce house dust mite exposure in the management of house dust mite sensitive allergic rhinitis.

SEARCH STRATEGY: Our search included the Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials Register (CENTRAL) (The Cochrane Library, Issue 2, 2005), MEDLINE (1951 to 2005) and EMBASE (1974 to 2005). No restrictions on the language of publication were employed. The bibliography of each paper and other published reviews were checked for further references. The date of the last search was May 2005.

SELECTION CRITERIA: Randomised controlled trials (with or without blinding), in which house dust mite control measures have been evaluated in comparison with placebo or other dust mite avoidance measures, in patients with clinician diagnosed allergic rhinitis and confirmed allergy to dust mite.

DATA COLLECTION AND ANALYSIS: Two authors independently checked titles and abstracts identified by the searches and full text copies of all papers of potential relevance were considered. Trials were graded for methodological quality using the Cochrane approach. Data extraction was performed in a standardised manner. Meta-analysis was neither possible nor appropriate, because of the heterogeneity of the patient groups studied; a narrative overview of the results is therefore presented.

MAIN RESULTS: Seven trials satisfied the inclusion criteria. Of these, only two studies investigating the effectiveness of mite impermeable bedding covers were of good quality; the remaining five studies were small and of poor quality. Two trials investigated the efficacy of acaricides, another two trials investigated the role of high-efficiency particulate air filters; the remaining three trials investigated the efficacy of bedroom environmental control programmes involving use of house dust mite impermeable bedding covers. Six of the seven trials showed that the interventions result in significant reductions in house dust mite load when compared with control. Of the house dust mite interventions studied to date, acaricides appear to be the most promising type of intervention, although the findings from the two studies which employed these interventions need to be interpreted with care because of their methodological limitations. Use of house dust mite impermeable bedding as an isolated intervention is unlikely to offer clinical benefit. No serious adverse effects were reported from any of the interventions.

AUTHORS' CONCLUSIONS: Trials to date have on the whole been small and of poor methodological quality, making it difficult to offer any definitive recommendations on the role, if any, of house dust mite avoidance measures in the management of house dust mite sensitive perennial allergic rhinitis. The results of these studies suggest that use of acaricides and extensive bedroom based environmental control programmes may be of some benefit in reducing rhinitis symptoms and, if considered appropriate, these should be the interventions of choice. Isolated use of house dust mite impermeable bedding is unlikely to prove effective.