In eosinophilic asthma, eosinophils, under the action of several cytokines including IL-5, accumulate within the bronchial tract where they release cytotoxic proteins, lipid mediators, cytokines, and chemokines that significantly contribute to airway hyperresponsiveness, inflammation, remodeling, and clinical exacerbations [21]. Here, IL5 is linked to airway hyperresponsiveness.