Asthma associated to rhinitis
A large amount of data show that AR and asthma are associated both epidemiologically and clinically, introducing the definition of united airway disease. The mechanisms underlying such association were initially suggested to start from the nose, including the loss of the protective and homeostatic effects of nasal function, the activation of a naso-bronchial reflex and the spread of allergic inflammation from the nose to the lower airways. Later, other factors such as microbial stimuli and systemic inflammatory mechanisms, involving bloodstream and bone marrow, were advocated.