IL13 and adult onset asthma: This phonotype suggests that she would benefit more from Feno and IgE-lowering therapies (eg, inhibition of IL-4 or IL-13 by dupilumab or, more speculatively, binding of TSLP with tezepelumab)36 than blood eosinophil-lowering therapies (eg, inhibition of IL-5 or IL-5R by mepolizumab or benralizumab).37, 38, 39 Indeed, Feno increases with IL-13 activity in the airway epithelium40—most classically with allergies, the hallmark of childhood asthma41—whereas the blood eosinophil count reflects systemic IL-5 activity and the pool of effector cells,24 a key biomarker for severe adult-onset asthma.41