High level of indoor air pollutant may cause aggravation of atopic diseases (AD) along with various allergic respiratory diseases especially to people who spend most of their lives indoors. The aim of this study is to evaluate the effect of air purifier on the reduction of relevant hazards in indoors and the improvement of AD. A total of 24 families, consisting 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 weeks. The assessment of air quality includes particles (PM2.5 and PM10), gaseous contaminants (CO, CO2, VOCs, formaldehyde, NO2) and density of offloating microorganisms. Severity of AD was assessed by SCORing Atopic Dermatitis (SCORAD) index and transepidermal water loss (TEWL). 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, p<0.01, respectively). However, the value of total IgE and eosinophil did not show significant changes in both groups compared with baseline. 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 purifer to prevent aggravation of AD.