Purpose: High level of indoor air pollutant may cause aggravation of atopic diseases long with various allergic respiratory diseases especially in people who spend mostly of their lives indoors. The aim of this study was to evaluate the effect of air purifier on the reduction of relevant hazards in indoors and the improvement of atopic dermatitis (AD). Methods: A total of 24 families, consisted of 18 AD families and 6 normal control families, were enrolled in this study. We examined air quality and AD severity before the installation of air purifiers and after twenty-four weeeks. The assessment of air quality included fine particles (particulate matter, PM2.5 and PM10), gaseous contaminants (CO, CO2, volatile organic compounds [VOCs], formaldehyde, NO2) and density of offloating microorganisms. Severity of AD was assessed by SCORing atopic dermatitis (SCORAD) index and transepidermal water loss (TEWL). Results: At the end of study, particular air pollutants and VOCs of gaseous air pollutants decreased in both groups (P<0.01). In AD group, SCORAD index decreased from 23.45±4.34 to 15.42±6.53 (.18.5%) and TEWL decreased from 33.78±5.16 to 26.89±5.66 (.18.7%) (P<0.01 and P<0.01, respectively). However, the value of total immunoglobulin E and eosinophil did not show significant changes in both groups compared with baseline. Conclusion: These results suggested that air purifier may improve severity of AD by reducing air pollutants like fine particles and VOCs. Our preliminary study could provide a basis for using air purifier to prevent aggravation of AD. (Allergy Asthma Respir Dis 2013;1:248-256)