The effects of particulate matter on atopic dermatitis symptoms are influenced by weather type: Application of spatial synoptic classification (SSC)

The effects of weather and air pollution on atopic dermatitis (AD) flares have not been well investigated. To investigate the effects of particulate matter (PM) on AD symptoms by weather type, a total of 125 young children (76 boys and 49 girls) under 6 years of age with AD living in Seoul, Korea, were enrolled as a panel and followed for 17 months between August 2013 and December 2014. AD symptoms were recorded on a daily basis, including itching, sleep disturbance, erythema, dry skin, oozing, and edema. Daily weather was classified into 7 categories according to spatial synoptic classification (SSC). Personal exposure to PM with an aerodynamic diameter less than 2.5 and 10 μm (PM2.5 and PM10, respectively) in each individual was estimated with time-weighted average concentrations considering outdoor and indoor levels of PMs and time to spend outdoors or indoors in a day. Generalized linear mixed models were used to analyze the effects of PM2.5 and PM10 on AD symptoms, controlling for ambient temperature, humidity, age, sex, SCORAD (SCORing of AD) at enrollment, fever, day of week, and topical corticosteroid use. A total of 20,168 person-days of symptom records were collected. The presence of AD symptoms was higher on dry polar (DP) days (45.4%, P < .0001) than on moist tropical (MT) days (37.7%, P < .0001). Overall, the risk of AD symptoms significantly increased with increased exposure to PM2.5 and PM10. Among the 7 weather types, the risks of AD symptoms caused by PM2.5 and PM10 exposure were significantly increased on dry moderate (DM) days, while not significant on the other weather types. In addition, lagged effect of PM2.5 up to 4 days was found on DM days. In conclusion, dry moderate weather type, particulate matters, and their modifying effects should be simultaneously considered for proper management of AD.