Clinical effects of air cleaners in homes of asthmatic children sensitized to pet allergens. A placebo-controlled trial of a HEPA air cleaner in the treatment of cat allergy.
Exposure to cat and dog allergens is very common in the Western World and is a serious cause of asthma in sensitized subjects.
                We sought to study the clinical effects of air cleaners in living rooms and bedrooms of asthmatic children sensitized to cat or dog allergens.
                Twenty asthmatic children sensitized to pet allergens (cat/dog) and with an animal at home participated in a double-blind, placebo-controlled, cross-over study in which the effects of air cleaners placed in the living room and bedroom for 3 months were compared with the effects of sham air cleaners. Before and after each study period, lung function, airway hyperresponsiveness (adenosine monophosphate), and peak flow variation were recorded. Cat and dog allergen levels were assessed in the filters of the air cleaners.
                After a 3-month intervention with active air cleaners, airway hyperresponsiveness decreased significantly, showing a 1.2 doubling dose increase of PC(20 )adenosine (P =.003). Peak flow amplitude also decreased (P =. 045). Substantial amounts of airborne cat and dog allergen were captured by the air cleaners in living rooms and bedrooms as well. Allergen levels in floor dust were not changed.
                In young asthmatic patients sensitized and exposed to pets in the home, application of air cleaners in living rooms and bedrooms was accompanied by a significant improvement in airway hyperresponsiveness and a decrease in peak flow amplitude. To evaluate the effect of a room high-efficiency particulate air (HEPA) cleaner on cat-induced asthma and rhinitis, 35 cat-allergic subjects who were living with one or more cats were studied in a double-blind, placebo controlled trial. After a 1 mo baseline period, subjects' bedrooms were equipped with an active or placebo air cleaner for the following 3 mo. Evaluations included monthly measurement of cat-allergen levels, daily morning, afternoon, and nighttime nasal- and chest-symptom scores, twice-daily measurement of peak-flow rates, daily medication scores, monthly spirometry, and methacholine (MCh) challenge testing before and after the study. Airborne allergen levels were reduced in the active-filter group as compared with the placebo group (p = 0.045). However, no differences were detected in settled-dust allergen levels (p = 0.485), morning, afternoon, or nighttime nasal-symptom scores (p = 0.769, 0.534, and 0.138), chest-symptom scores (p = 0.388, 0.179, and 0.215), sleep disturbance (p = 0.101), morning or afternoon peak-flow rates (p = 0. 424 and 0.679), or rescue medication use (nasal, p = 0.164, chest, p = 0.650), respectively. Although the combination of a HEPA room air cleaner, mattress and pillow covers, and cat exclusion from the bedroom did reduce airborne cat-allergen levels, no effect on disease activity was detected for any parameter studied.
The available trials are too small to provide evidence for or against the use of air filtration units to reduce allergen levels in the management of pet-allergic asthma. Adequately powered trials are needed. There are no trials of other allergen reduction measures, such as pet washing or possibly pet removal.