Rhinitis and asthma commonly coexist in allergic patients. This observation might be attributable to their coexistence in time, but it is also possible that both diseases are the opposite poles of a single disease affecting the respiratory system, or even an anomalous systemic immune response to the allergen. Nose-lung interactions have been widely studied from epidemiological, physiopathological, aetiological and pharmacological aspects. In the present article we review this topic and its main clinical implications.