Supplementary Material for: Cumulative Evidence for Association of Acetaminophen Exposure and Allergic Rhinitis

<b><i>Background:</i></b> Several studies have linked acetaminophen exposure to the risk of allergic rhinitis, with controversial results. <b><i>Methods:</i></b> A systematic search of PubMed, Embase, Cochrane Library, and Web of Science was conducted up to December 1, 2019. We included observational studies that examined the association between acetaminophen exposure and the risk of allergic rhinitis. Two reviewers independently extracted data and assessed study quality. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using random-effects meta-analysis. <b><i>Results:</i></b> Eighteen studies with 870,492 participants were included. Analysis showed that acetaminophen exposure was associated with an increased risk of allergic rhinitis (OR: 1.54, 95% CI: 1.41–1.69). Also, early exposure and exposure in the past year to acetaminophen was positively associated with risk of allergic rhinitis (OR: 1.34, 95% CI: 1.21–1.49 and OR: 1.74, 95% CI: 1.48–2.04, respectively). The risk of allergic rhinitis was greater for people who had acetaminophen exposure once per month over the past year (OR: 1.90, 95% CI: 1.60–2.26) compared to once per year (OR: 1.28, 95% CI: 1.11–1.48). <b><i>Conclusion:</i></b> With our meta-analysis, we provide the evidence that exposure to acetaminophen is associated with an increased risk of allergic rhinitis. In addition, acetaminophen exposure in early life and acetaminophen exposure in the past year are positively associated with the risk of allergic rhinitis. Future research is needed to evaluate whether the association is causal.