<p>The potential for vitamin D₃ supplementation as adjunctive therapy in allergic rhinitis (AR) management remains a topic of considerable interest. Studies have investigated the relationship between serum vitamin D levels and AR severity, with conflicting results. To evaluate the impact of vitamin D₃ supplementation on symptom severity and IgE levels in patients with persistent allergic rhinitis (AR), and to assess the role of sustained supplementation in achieving long-term benefits. A randomized, double-blind, prospective interventional study was conducted at a teaching institute in India with 600 AR patients randomized into three groups: Group A (intranasal corticosteroids and placebo), Group B (intranasal corticosteroids and vitamin D₃ supplementation with maintenance doses), and Group C (intranasal corticosteroids and vitamin D₃ without maintenance doses). A control group of 200 healthy individuals was also included. Vitamin D₃, IgE levels, and Total Nasal Symptom Score (TNSS) were measured at baseline, 2 months, and 6 months. At baseline, 81.66% of AR patients had suboptimal vitamin D₃ levels compared to 65% in the control group. Group B showed the most significant improvement in vitamin D₃ levels, with 80% achieving normal levels by 6 months. TNSS and IgE levels also improved significantly in Group B, with sustained reductions compared to Groups A and C (<i>p</i> &lt; 0.001). Group C showed a rebound in symptoms and IgE levels after discontinuation of supplementation. Sustained vitamin D₃ supplementation significantly improves symptom severity and IgE levels in patients with persistent AR. These findings suggest vitamin D₃ as a promising adjunct to standard AR treatment.</p>