Background: Vitamin D supplementation has been proven to be effective in the treatment of allergic rhinitis (AR). Objective: We conducted the present study to explore the role and efficacy of vitamin D adjuvant therapy for the treatment of inflammation in patients with AR. Methods: Out of 127 patients with potential eligible AR, 60 were randomly assigned into two groups and were finally included in our analysis (n=30 for each intervention). The patients with potential eligible AR were randomly allocated to intervention with desloratadine citrate disodium (DCD, 8.8 mg/day) without and with vitamin D3 nasal drops (1.5х106 IU, once/week) for four weeks. Thirty healthy control subjects were included in our study. We assessed the changes in the serum 25(OH)D, peripheral blood eosinophils, interleukin (IL)-4 levels, and nasal symptoms. Serum 25(OH)D, peripheral blood eosinophils, and IL-4 levels were detected respectively with liquid chromatography-tandem mass spectrometry (LC-MS/MS), a blood detector, and enzyme-linked immunosorbent assay. Results: Our patients who received vitamin D3 adjuvant therapy had a higher serum 25(OH)D level (47.57 ± 2.83 vs. 31.51 ± 2.95 ng/ml, p=0.000) and lower AR symptoms score (2.07 ± 1.89 vs. 3.37 ± 1.50, p=0.005), serum IL-4 (10.38 ± 3.41 vs. 12.79 ± 5.40 pg/ml, p=0.043), and peripheral blood eosinophils (0.34 ± 0.09 vs. 0.41 ± 0.10 109/l, p=0.003) compared with DCD single treatment. The efficacy rates of DCD with and without vitamin D3 in AR were 97% and 84%, respectively. Conclusion: Nasal vitamin D3 combined with DCD could improve the clinical symptoms of AR. Vitamin D3 adjunct therapy showed significant effects on inhibiting inflammation in patients with AR. We concluded that vitamin D3 supplementation could be an effective adjuvant therapy in AR patients.