Effects of air purifiers on patients with allergic rhinitis: A multicenter, randomized, double-blind, and placebo-controlled study

Purpose: Exposure to particulate matter (PM) is a well-known risk factor in the triggering and exacerbation of allergic airway dis-ease. Indoor environments, where people spend most of their time, are of utmost importance. To assess the effects of air purifiers [equipped with high-efficiency particulate air (HEPA) filters] on allergic rhinitis (AR) in adult patients, we performed a multicenter, randomized, double-blind, and placebo-controlled study. Materials and Methods: Patients with house dust mite (HDM)-induced AR were randomly assigned to either active or mockup (placebo) air-purification groups. Two air purifiers (placed in living room and bedroom) were operated for 6 weeks in each home environment. The primary study endpoint was to achieve improvement in AR symptoms and medication scores. Secondary end-points were to achieve improvement in the quality of life (QoL) and visual analog scale (VAS) scores, as well as in the indoor (bed-room and living room) concentrations of PM_2.5 and PM₁₀. Results: After 6 weeks of air purifier use, medication scores improved significantly in the active (vs. placebo) group, although sub-jective measures (symptoms, VAS, and QoL scores) did not differ. Bedroom PM_2.5 concentrations initially exceeded living room or outdoor levels, but declined (by up to 51.8%) following active purifier operation. Concentrations of PM_2.5 in living room and PM₁₀ in bedroom and living room were also significantly reduced through active purification. Conclusion: The use of air purifiers with HEPA filters significantly reduced medication requirements for patients with HDM-in-duced AR and significantly lowered indoor PM_2.5 concentrations, regardless of room placement. Active intervention to reduce household air pollutants may help improve allergic airway disease (clinicaltrials.gov NCT03313453).