Background: Sinonasal polyps and allergic rhinitis are prevalent disorders that significantly diminish the standard of living for those who suffer from them. Variants in the interleukin 21 (IL-21) gene have been linked to an increased risk of developing several immune-related diseases. Objective: To examine the correlation between IL-21 gene polymorphisms and the likelihood of developing allergic rhinitis and sinonasal polyps. Patients and Methods: Patients with sinonasal polyps and allergic rhinitis, in addition to a control group, participated in this cross-sectional study. Controls (Group A), patients with AR (Group B), and patients with SNP (Group C) comprised the patient population. TaqMan SNP Genotyping assays were utilised to genotype the IL-21 gene SNP (rs6822844). To identify associations, clinical and genetic data were evaluated. Results: A notable disparity in the distribution of genotypes was identified in the case-control comparison (p < 0.006). In particular, individuals diagnosed with AR had 32 %GG genotypes, 56 %GT genotypes, and 12% TT genotypes. In contrast, the control group demonstrated a mere 4% TT genotypes, 12% GG genotypes, and 84% GT genotypes. The genotype distribution of the SNP patients differed significantly (p < 0.002), with 16% carrying the GG genotype, 60% carrying the GT genotype, and 24% carrying the TT genotype. The distribution of genotypes in the control group comprised 4% TT genotypes, 84% GT genotypes, and 12% GG genotypes. Conclusion: It is possible that Egyptians with certain IL-21 gene variants are more likely to suffer from allergic rhinitis and sinonasal polyps.