House dust mite avoidance measures for perennial allergic rhinitis.

BACKGROUND: This is an update of a Cochrane Review first published in The Cochrane Library in Issue 4, 2001 and previously updated in 2003 and 2007.It is estimated that in developed countries approximately 30% of the general population suffer from one or more allergic disorders, of which allergic rhinitis is particularly 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 4, 2009), MEDLINE and EMBASE. The date of the last search was 31 December 2009. 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 screened titles and abstracts, graded methodological quality using the Cochrane approach and extracted data. Meta-analysis was neither possible nor appropriate due to heterogeneity of the patient groups studied. MAIN RESULTS: Nine trials involving 501 participants satisfied the inclusion criteria. Only two studies investigating the effectiveness of mite impermeable bedding covers were of good quality; the remaining seven 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 (HEPA) filters. One trial, using a factorial design, investigated the efficacy of both acaricide and house dust mite impermeable bedding covers in isolation and combination; the remaining four trials investigated the efficacy of bedroom environmental control programmes involving use of house dust mite impermeable bedding covers. Seven of the nine trials reported that, when compared with control, the interventions studied resulted in significant reductions in house dust mite load. Of the interventions studied to date, acaricides appear to be the most promising type of intervention, although the findings from these studies need to be interpreted with care because of their methodological limitations. 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.