IL4 and asthma: The analysis of overall population revealed the significant positive association between IL4 gene -589C/T polymorphism and the risk of asthma across all genetic models; including dominant model (OR = 1.22, 95% CI = 1.04–1.44, P = 0.01, REM), recessive model (OR = 1.17, 95% CI = 1.08–1.27, P < 0.001, FEM), allelic model (OR = 1.21, 95% CI = 1.09–1.33, P < 0.001, REM), and TT vs. CC model (OR = 1.34, 95% CI = 1.18–1.52, P < 0.001, FEM), except CT vs. TT model (OR = 1.13, 95% CI = 0.95–1.34, P = 0.17, REM) (Fig. 2).