Nasal disease and asthma.

The nose plays a primary role within the airways, working as a filter and air-conditioner, together with other important functions. Thus, it is not surprising that nasal diseases are associated with several other comorbidities, including both upper and lower airways, such as bronchial hyperresponsiveness (BHR) and asthma. Several studies have investigated the relationship existing between the upper and the lower airways and new insights are rising. Nevertheless, some uncertainties still remain, mainly because nasal disorders are quite heterogeneous, overlapping (i.e. rhinitis-rhinosinusitis-sinusitis, acute or chronic, allergic or non-allergic) and difficult to diagnose, so that, frequently, many studies don’t differentiate between the various conditions. For this reason, the purpose of this review is to systematically analyze present epidemiological, pathophysiological and clinical data on the relationship between nasal diseases and asthma, splitting up three main conditions: allergic rhinitis, chronic rhinosinusitis and nasal polyposis.