Objective  To explore the effect of air pollution and meteorological factors on the outpatient visits.

  Methods  Data of outpatient visits for dermatitis in the West China Hospital of Sichuan University, air pollutants data (SO₂, NO₂, PM₁₀) and meteorological data (barometric pressure, temperature, relative humidity, wind speed)from January 1, 2011 to December 31, 2015 were collected. Distributed lag nonlinear model was used to analyze the influence of air pollution and meteorological factors on the outpatient visits.

  Results  The daily outpatient amountof dermatitis was positively correlated with PM₁₀ and wind speed, and negatively correlated with SO₂ and temperature. Univariate analysis showed that therelative risk of daily outpatient visits for a 10 μg/m³ increment in SO₂ and NO₂ were 1.003 (95%CI: 1.002-1.004) and 1.002 (95%CI:1.001-1.002) respectively. And the relative risk of daily outpatient visits for a 10% increment in relative humidity was 0.996 (95%CI:0.994-0.997).Multi-pollutant models indicated that air pollutant concentrations were significantly associated with the daily outpatient amount of dermatitis. Distributed lag models showed that the effects of SO₂, NO₂ and PM₁₀ on the daily outpatient amount of dermatitis were mainly observed on the day of exposure. Relative humidity had negative effect on the daily outpatient amount of dermatitis on the day of exposure, in Lag2 days and in Lag4 days.

  Conclusion  Air pollutants may be a risk factor for dermatitis, and relative humidity can reduce the risk of dermatitis.