Over the past 10 years, there has been increasing recognition of the interaction between the upper and lower airways in patients with a variety of infectious and inflammatory illnesses, including allergic rhinitis, rhinosinusitis, and asthma. Epidemiologic and mechanistic links have been proposed to demonstrate these relationships and to offer possible etiologic explanations to account for these observations. Among patients with upper respiratory illnesses, cough can be seen as a common symptom, both from the direct influences of upper airway inflammation, which incite reflex changes and bronchospasm, and from the exacerbation of associated pulmonary processes, such as asthma. Despite this increasing awareness of interaction between the upper and lower airways, the influence of both upstream and downstream respiratory inflammatory processes on laryngeal pathophysiology has not been extensively studied. Research suggests, however, that both direct stimulatory effects on the larynx and secondary effects of mucus production and mucus trafficking can create a range of laryngeal symptoms, including cough. This review discusses the interaction of the upper and lower airway in respiratory disease, and focuses on the effect of these respiratory processes on laryngeal inflammation, function, and symptoms.
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