IL-13 produced in the airway promotes the survival and migration of eosinophils, the activation of macrophages, the production of mucus by airway epithelial cells, the transformation of airway fibroblasts to myofibroblasts leading to collagen deposition and tissue remodeling, and airway hyper-responsiveness, all of which are key features of allergic asthma (Ingram and Kraft, 2012). Here, IL13 is linked to allergic asthma.