“Rhinitis” is a general term used to indicate nasal congestion, nasal obstruction, and rhinorrhea. Although it etymologically implies an inflammatory phenomenon, not all types of rhinitis are associated with inflammation and may be due to mucosal hyperresponsiveness to either exogenous or endogenous stimuli. Non-allergic rhinitis (NAR) describes a subset of rhinopathies in which patients exhibit symptoms associated with rhinitis but in whom allergy has been ruled out via skin or in vitro testing. The differential diagnosis of NAR is broad and patients may exhibit both allergic and non-allergic types of disease. Research in the realm of NAR has attempted to better elucidate this condition. Proposed mechanisms include an exaggerated response to environmental triggers or free radicals, neural dysregulation, and chemoreceptor activation. The purpose of this excerpt is to briefly review those theories that critically examine the underlying pathophysiology of this heterogeneous nasal disease.