We estimated the exposure to ambient air pollutants and analyzed the associations with allergic diseases. We enrolled 177 children with atopic dermatitis (AD) and 70 asthmatic adults living in Seoul Metropolitan Area, Korea, and followed for 17 months between August 2013 and December 2014. Parents or patients recorded symptom scores on a daily basis. Exposure to particulate matter with a diameter <10 mu m (PM10) and nitrogen dioxide (NO2) was estimated in four different ways in each individual, using the AQ1 (measurements from the nearest air quality monitoring station to residential houses), AQ2 (measurements modified from AQ1 with the indoor level of air pollutants and time activity of each individual), AQ1-DI, and AQ2-DI (measurements modified from AQ1 and AQ2, respectively, with daily inhalation intakes of air pollutants). A generalized linear mixed model (GLMM) was used to analyze the associations between exposure metrics and clinical symptoms after adjusting for ambient temperature and humidity, age, season, gender, and time trend. The exposure metrics for PM10 and NO2 showed different distributions. Symptoms of AD and asthma were positively associated with exposure to PM10, but not NO2, in all exposure metrics. The effect size of PM10 exposure on asthma symptoms was slightly greater inmetrics with inhalation capacity (AQ-DIs) than in thosewithout (AQs). This pattern was not observed in AD. Exposure to PM10 is associated with symptomag gravation in childhood AD and adult asthma. Different exposure estimates may be used to evaluate the impact of air pollution on different allergic diseases. (C) 2016 Elsevier B.V. All rights reserved.