The upper airway (extending from the nares to larynx) fulfills essential physiologic functions, including sensation, air conditioning, filtration, and communication. As the portal of entry for the respiratory tract, the upper airway's sentinel function is performed by the olfactory and trigeminal nerves. Sensory (eye, nose and throat) irritation figures prominently in symptom reporting in so-called "problem buildings," as well as in industrial exposures to irritant gases, vapors, and smokes. Both irritants and allergens can alter function in the upper airway, leading to loss of air conditioning and filtering due to airflow obstruction and hypersecretion. Increasing evidence points to a "unified airway" model of pathogenesis (in which rhinitis may precede the development of asthma). The spectrum of occupational irritant- and allergen-related upper airway health effects-including sensory irritation, olfactory dysfunction, rhinitis, sinusitis, nasal septal perforation, and sinonasal cancer-is reviewed in this article.