| RCT | Randomized controlled trials |
| CI | Confidence interval |
| SMD | Standardized mean difference |
| AR | Allergic rhinitis |
| 25-(OH)D | 25-hydroxyvitamin D |
| IL | Interleukin |
| Treg | Regulatory T cell |
| SD | Standard deviation |
| PRISMA | Preferred Reporting Items for Systematic Reviews and Meta-Analyses |
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