The results show that asthma is significantly correlated with elevated levels of IL-5 and IL-9 [IL-5, odds ratio (OR) = 1.112, 95% confidence interval (CI): 1.009–1.224, P = 0.032; IL-9, OR = 1.111, 95% CI: 1.013–1.219, P = 0.025], and the results of IVW are also supported by Radial-MR. The gene discussed is IL9; the disease is asthma.