The relationship between outdoor air pollutants and atopic dermatitis of adults: A systematic review and meta-analysis

Background: Atopic dermatitis (AD) poses a significant disease burden in adults. Environmental factors are essential in its pathogenesis.Objective: Given the possible role of air pollutants in allergic diseases, it is worthwhile to summarize the effects of outdoor air pollution on adult AD.Methods: We undertook a systematic review based on PubMed and EMBASE as of August 16, 2021, and found 20 relevant studies. A random-effects meta-analysis was carried out.Results: Regarding long-term effects (within months to years), traffic-related air pollution and particulate matter < 2.5 mu m in diameter (PM2.5, per 10 mu g/m3 increment) are associated with the prevalence of adult AD (OR 1.40, 95%CI [1.24, 1.58] and 1.67, 95%CI [1.26, 2.21]). Exposures to PM2.5 and nitrogen dioxide are associated with incident AD, with ORs of 2.30 (95%CI: 1.25, 4.25) and 1.30 (95%CI: 1.04, 1.61) per 10 mu g/m3 increment. In terms of short term effects (within days), exposure to particulate matter < 10 mu m in diameter (PM10) and sulfur dioxide (SO2) are associated with exacerbations of AD at lag day 0 based on those time-series studies, with an excessive risk of 2.9%, in particular, per 10 mu g/m3 increment in SO2 exposure. In addition, both short-term and long-term exposures to these air pollutants are associated with AD symptoms (eczema, pruritus, and sleep disturbance).Conclusions: Outdoor air pollutants exert both short-term and long-term adverse effects on adult AD, contributing to its development, severity and exacerbation of symptoms. The influence of air pollution should be considered in the management of adult AD.