The unified allergic airway describes patients who have both asthma and allergic rhinitis. Both conditions have similar underlying pathophysiology in terms of T-helper 2 (Th2) cell activation. Patients with unified allergic airway disease have a greater burden in terms of impaired quality of life, and the presence of airway hyper-responsiveness (AHR) to methacholine is a hallmark of their underlying asthmatic inflammatory process. Targeting the Th2 allergic airway with a topical antihistamine may improve airway hyperresponsiveness.