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Original Investigation
April 21, 2021

Association of Wildfire Air Pollution and Health Care Use for Atopic Dermatitis and Itch

Author Affiliations
  • 1Department of Dermatology, University of California, San Francisco
  • 2Dermatology Service, San Francisco Veterans Affairs Medical Center, San Francisco, California
  • 3School of Public Health, University of California, Berkeley
  • 4Department of Epidemiology and Biostatistics, University of California, San Francisco
  • 5Department of Medical Statistics, London School of Hygiene & Tropical Medicine, London, United Kingdom
  • 6Office of Health Equity, California Department of Public Health, Richmond
  • 7Division of Occupational and Environmental Medicine, University of California, San Francisco
JAMA Dermatol. 2021;157(6):658-666. doi:10.1001/jamadermatol.2021.0179
Key Points

Question  Is short-term exposure to wildfire-associated air pollution associated with the frequency of outpatient clinic visits for atopic dermatitis and itch?

Findings  In this cross-sectional time-series study of 8049 dermatology clinic visits by 4147 patients, short-term wildfire-associated air pollution exposure was significantly associated with increased rates of weekly appointments. The increases were seen in pediatric and adult appointments for atopic dermatitis and in pediatric appointments for itch.

Meaning  In this study, short-term exposure to poor air quality due to wildfire smoke appeared to be associated with exacerbations of patients’ skin conditions as measured by increased use of health care services for the management of atopic dermatitis and itch.


Importance  Air pollution is a worldwide public health issue that has been exacerbated by recent wildfires, but the relationship between wildfire-associated air pollution and inflammatory skin diseases is unknown.

Objective  To assess the associations between wildfire-associated air pollution and clinic visits for atopic dermatitis (AD) or itch and prescribed medications for AD management.

Design, Setting, and Participants  This cross-sectional time-series study assessed the associations of air pollution resulting from the California Camp Fire in November 2018 and 8049 dermatology clinic visits (4147 patients) at an academic tertiary care hospital system in San Francisco, 175 miles from the wildfire source. Participants included pediatric and adult patients with AD or itch from before, during, and after the time of the fire (October 2018 through February 2019), compared with those with visits in the same time frame of 2015 and 2016, when no large wildfires were near San Francisco. Data analysis was conducted from November 1, 2019, to May 30, 2020.

Exposures  Wildfire-associated air pollution was characterized using 3 metrics: fire status, concentration of particulate matter less than 2.5 μm in diameter (PM2.5), and satellite-based smoke plume density scores.

Main Outcomes and Measures  Weekly clinic visit counts for AD or itch were the primary outcomes. Secondary outcomes were weekly numbers of topical and systemic medications prescribed for AD in adults.

Results  Visits corresponding to a total of 4147 patients (mean [SD] age, 44.6 [21.1] years; 2322 [56%] female) were analyzed. The rates of visits for AD during the Camp Fire for pediatric patients were 1.49 (95% CI, 1.07-2.07) and for adult patients were 1.15 (95% CI, 1.02-1.30) times the rate for nonfire weeks at lag 0, adjusted for temperature, relative humidity, patient age, and total patient volume at the clinics for pediatric patients. The adjusted rate ratios for itch clinic visits during the wildfire weeks were 1.82 (95% CI, 1.20-2.78) for the pediatric patients and 1.29 (95% CI, 0.96-1.75) for adult patients. A 10-μg/m3 increase in weekly mean PM2.5 concentration was associated with a 7.7% (95% CI, 1.9%-13.7%) increase in weekly pediatric itch clinic visits. The adjusted rate ratio for prescribed systemic medications in adults during the Camp Fire at lag 0 was 1.45 (95% CI, 1.03-2.05).

Conclusions and Relevance  This cross-sectional study found that short-term exposure to air pollution due to the wildfire was associated with increased health care use for patients with AD and itch. These results may provide a better understanding of the association between poor air quality and skin health and guide health care professionals’ counseling of patients with skin disease and public health practice.

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