IL4 and asthma: The final findings indicated strong significant association between IL-4 C33T polymorphism and asthma risk in European population across dominant model (OR = 1.23, 95% CI = 1.01–1.50, P = 0.03, FEM), recessive model (OR = 2.94, 95% CI = 1.54–5.62, P = ≤0.001, FEM), allelic model (OR = 1.30, 95% CI = 1.10–1.54, P = ≤0.001, FEM) and CC vs. TT (OR = 3, 95% CI = 1.56–5.76, P = ≤0.001, FEM).