A double-blind study of the effectiveness of a high-efficiency particulate air (HEPA) filter in the treatment of patients with perennial allergic rhinitis and asthma

Abstract

This study was designed to assess the effectiveness of a high-efficiency particulate air (HEPA) filter in alleviating allergic respiratory symptoms. Thirty-two patients were studied who had symptomatic perennial rhinitis and/or asthma during the fall and winter months and had a positive skin test with house dust or house dust-mite extract. An ENVIRACAIRE room air cleaner was placed in the bedroom for 8 weeks. In a random manner, the active filter was used for 4 weeks and a blank filter for 4 weeks. There was an average 70% reduction in the particulate matter ≥0.3 μm with the HEPA filter. In a double-blind design, results were assessed by analysis of the patients' symptom/medication scores and subjective evaluation. For the total study, there was no difference in the total symptom/medication scores or individual symptom scores during the placebo and active-filter periods. Analysis of the last 2 weeks of each filter period in which respiratory infection was absent demonstrated definite differences in total and individual symptoms, suggesting active-filter benefit. Patients' subjective responses also suggested benefit from the filter. The overall impression is that the HEPA filter can reduce allergic respiratory symptoms.