Allergic asthma is classically defined by allergen-induced airway inflammation and is represented by elevated serum immunoglobin E (IgE), type 2 cytokine (interleukins-4, -5, and -13 [IL-4, IL-5, IL-13]) production, and sputum eosinophilia (>1%-3%) (15, 16). Here, IL4 is linked to allergic asthma.