Clinical Question: Do impermeable bed and pillow covers improve symptoms of allergic rhinitis?

Setting: Outpatient (any)

Study Design: Randomized controlled trial (double-blinded)

Synopsis: Use of impermeable bed and pillow covers by persons with allergies reduces exposure to dust mite allergens—but is that enough to improve symptoms? Previous studies have been small and poorly designed, and have provided conflicting results. In this trial, subjects eight to 50 years of age who were allergic to dust mites were randomized (allocation concealed) to receive impermeable (n = 139) or permeable (n = 140) bed covers. Participants were recruited from specialty clinics, from general practices, and by advertisements. Persons with pets in the home, persons using oral or high-dose inhaled steroids, and those taking cyclosporine or regular doses of antibiotics were excluded.

Measurements were taken at baseline and at the 12-month follow-up visit between September and December, the peak months for Dutch dust mites. Nineteen subjects in the control group and 24 subjects in the group using impermeable covers were lost to follow-up, most often because they moved or because of a protocol violation. The primary outcome was a 100-point allergy symptom severity score. The groups were similar at baseline, and analysis was by intention-to-treat for participants with a 12-month outcome measurement.

Although allergen counts were significantly lower in the beds of subjects with impermeable bed covers, and while both groups experienced an improvement in symptoms, the degree of improvement did not differ significantly between the groups (−9.8 points in the impermeable cover group versus −10.9 points in the control group; P =.8). There also was no significant difference in daily symptom scores and in the results of the nasal allergen provocation test. The study was powered to detect at least a 25 percent reduction in the symptom score.

Bottom Line: In persons with allergic rhinitis who are sensitive to dust mites, use of impermeable bed and pillow covers does not improve symptoms more than use of conventional covers. (Level of Evidence: 1b)