Background: There is a dearth of real-world evidence studies focused on allergy immunotherapy (AIT) use among patients with allergic rhinitis (AR). Objective: This study examined claims data of AR patients residing in the United States to assess patient characteristics and health outcomes. Methods: AR patients were identified in the IBM MarketScan database between January 1, 2014, and March 31, 2017. Patients receiving AIT were identified with relevant billing codes (earliest AIT claim for vaccine as the index date); patients without AIT were identified with claims that contained a diagnosis code for AR (earliest AR claim as the index date). All the patients were required to have continuous enrollment 12 months prior to and following their index date. AIT patients reaching 25+ injection claims were analyzed as a separate maintenance cohort. Patients were assessed for demographic characteristics, comorbid conditions, and health care utilization. Results: A total of 2,334,530 AR patients were included; 103,207 had at least one AIT claim, with 45,279 (43.9%) of these patients reaching maintenance. Patients who reached AIT maintenance presented higher rates of baseline comorbidities than both the full AIT cohort and the patients with no AIT claims, including asthma (34.6% versus 30.1% versus 7.5%) and upper respiratory tract infections (63.1% versus 60.3% versus 34.2%). From baseline to follow-up, maintenance AIT patients demonstrated reductions in all AR-related comorbidities assessed, along with reductions in all-cause and AR-related service utilization. Conclusion: Patients initiating AIT presented the greatest need for therapeutic intervention, as evidenced by higher allergy-related comorbidities; those who reached maintenance demonstrated improved outcomes following the initiation of therapy. Continued efforts to increase patient awareness and adherence to AIT are needed.