Koji Kawakami

Background Pediatric allergic rhinitis (AR), including cedar pollinosis (CP), is increasing in Japan. We investigated the effects of sublingual immunotherapy (SLIT), which has limited studies of its effectiveness in real‐world settings, on children with CP. Methods This retrospective cohort study used a claim database in 2018–2021. Children aged ≤15 years with CP records in 2019 were eligible and were followed up through 2021. We included 2962 CP children undergoing SLIT and 547 who were not. The medication score was used to evaluate SLIT effectiveness in the cedar pollen dispersal season each year. Adverse events and the occurrence of allergic diseases were also evaluated. Results Medication score was higher in the SLIT group during the index period but lower in 2021 compared to the non‐SLIT group (mean ± standard deviation: 5.17 ± 2.39 and 4.74 ± 2.38 in 2019, 3.13 ± 2.30 and 3.55 ± 2.48 in 2021, respectively). The adjusted mean difference between groups from 2019 to 2021 was −0.62 (95% confidence interval: −0.86 to −0.39, p < .0001), and the medication score was reduced in the SLIT group (risk ratio: 1.2: 1.1 to 1.3). The occurrence of adverse events involving abdominal disorders (adjusted odds ratio [aOR]: 0.64: 0.51 to 0.81), asthma exacerbation (aOR: 0.37: 0.24 to 0.57), and allergic diseases involving hay fever unrelated to CP (aOR: 0.60: 0.45 to 0.80) or asthma (aOR: 0.71: 0.58 to 0.86) was lower in the SLIT group. Conclusion In children with CP, SLIT is effective, well tolerated, and could decrease the occurrence of other allergic diseases.