Objective: To analyze the efficacy of allergen subcutaneous injection immunotherapy in patients with allergic rhinitis. Methods: Fifty patients with allergic rhinitis admitted from May 2023 to May 2025 were selected as study subjects and randomly divided into a control group and an observation group, with 25 patients in each group. The control group was treated with budesonide nasal spray, while the observation group received allergen subcutaneous injection immunotherapy in addition to the control treatment. The treatment efficacy, adverse reactions, symptom improvement time, and immune indicators were compared between the two groups. Results: The observation group showed a higher disease treatment efficacy than the control group (p < 0.05); the incidence of adverse reactions in the observation group was not statistically significant compared to the control group (p > 0.05); the observation group had a shorter symptom improvement time for nasal obstruction, rhinorrhea, and sneezing than the control group (p < 0.05); before treatment, there was no statistical significance in immune indicators between the two groups (p > 0.05); after treatment, CD3⁺ and CD4/CD8⁺ in the observation group were higher than those in the control group (p < 0.05). Conclusion: Allergen subcutaneous injection immunotherapy in patients with allergic rhinitis can improve disease treatment efficacy, alleviate clinical symptoms, and enhance immune function. This therapy is safe and has clinical application value.