Impermeable bed covers don't help allergic rhinitis

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

Synopsis Impermeable bed and pillow covers reduce the exposure of allergic patients 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 randomised controlled (double blinded) trial, adults and children aged 8 to 50 years who were allergic to dust mites were randomised (allocation concealed) to receive either impermeable (n = 139) or permeable (n = 140) bed covers. They were recruited from specialty clinics and general practices and by advertisements. Patients with pets in the home, those using oral or high dose inhaled steroids, and those taking cyclosporine or regular doses of antibiotics were excluded. Baseline and 12 month follow up measurements were made between September and December, the peak months for dust mites in the Netherlands. Nineteen patients in the control group and 24 in the impermeable cover group 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 patients with a 12 month outcome measurement.

Although allergen counts were significantly lower in the beds of patients with impermeable bed covers, and although both groups experienced an improvement in symptoms, there was no significant difference between groups in the degree of improvement (9.8 points in the impermeable cover group v 10.9 points in the control group; P = 0.8). There was also 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% reduction in the symptom score.

Bottom line Impermeable bed and pillow covers do not improve symptoms more than conventional covers in patients with allergic rhinitis who are sensitive to dust mites.

Level of evidence 1b (see www.infopoems.com/resources/levels.html); individual randomised controlled trials (with narrow confidence interval).