In this study, after treatment with an IL-9 neutralizing antibody, the fraction of Th2 cells in the spleen of allergic rhinitis mice decreased, the expression of cytokines such as IL-4, IL-5, IL-13, and IL-9 in the corresponding nasal mucosa decreased, and its mRNA also decreased, indicating the anti-inflammatory effect of the IL-9 neutralizing antibody. This evidence concerns the gene IL9 and allergic rhinitis.