Air Pollution and Weather Conditions Are Associated with Daily Outpatient Visits of Atopic Dermatitis in Shanghai, China

<b><i>Background:</i></b> Non-optimum weather conditions and air pollution have the potential to increase the risk of atopic dermatitis (AD), but the associations are rarely evaluated, especially in developing countries. <b><i>Objective:</i></b> To investigate the independent influence and interaction effects of meteorological factors and air pollutants on the onset of AD. <b><i>Methods:</i></b> Daily data on outpatient visits of AD were obtained from Shanghai Dermatology Hospital and comprised 34,633 patients during the period from January 2013 to December 2018. Meteorological conditions and air pollutant concentrations in Shanghai, China, during the 6-year period were collected. We applied the overdispersed generalized additive model and the distributed lag model to explore the short-term cumulative effects of environmental factors on AD. <b><i>Results:</i></b> AD symptoms were aggravated by extreme low temperature (1st percentile, 0.5°C) (RR = 1.32, 95% CI: 1.16–1.51) and per 10 unit decrease of humidity (RR = 1.10, 95% CI: 1.12–2.47). The increased concentration of air pollutants except ozone (O₃) contributed to the increased risk of AD outpatients. A 10 μg/m³ increase in sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) were associated with 6.03% (95% CI: 2.29%, 9.91%), and 1.96% (95% CI: 0.46%, 3.48%) increase of AD outpatients. AD patients in the 8- to 17-year-old group were most susceptible to extreme low temperature, and patients in the 0- to 7-year-old group were most susceptible to air pollutants, including particulate matter (PM₁₀), SO₂, and NO₂. Men were more sensitive to the effects of extreme low temperature than women, while women were more vulnerable to air pollutants. The adverse effects of SO₂ and NO₂ on AD can be enhanced significantly by the warm season or other pollutants. <b><i>Conclusion:</i></b> Exposure to a lower temperature, lower humidity, and higher levels of air pollutants is significantly associated with increased risks of AD incidence. These impacts were more pronounced in children less than 7 years old, women, and warm seasons.