Rhinitis is defined as an inflammatory condition that affects the nasal mucosa. The symptoms of rhinitis include nasal obstruction, hyperirritability, and hypersecretion. Rhinitis can be caused by a variety of different allergic and nonallergic conditions (Table 14–1). The incidence of rhinitis seems to have increased since the Industrial Revolution. One in five Americans is estimated to be afflicted with rhinitis.
Table 14–1Types of rhinitis. ||Download (.pdf) Table 14–1 Types of rhinitis.
|Allergic Rhinitis ||Infectious Rhinitis ||Nonallergic, Noninfectious Rhinitis ||Miscellaneous |
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Allergic rhinitis is one of the most common chronic conditions in the United States. Of the approximately 50 million U.S. individuals who have rhinitis, many do not have an allergic cause to their rhinitis. The symptoms of nonallergic rhinitis include nasal obstruction, hypersecretion, and irritability, none of which is due to allergy.
Airflow through the nose is more efficient in gas exchange and requires less energy than mouth breathing. The nose serves as the initial conduit into the airway. As such, it has important functions of warming, humidifying, and cleansing the air that we breathe. The nasal cycle consists of simultaneous sympathetic and parasympathetic modulation in opposite directions on opposite sides of the nose. The nasal cycle can alter airflow in 1 nostril by up to 80%, while maintaining total airflow.
From anterior to posterior, the different structural elements of the nose act together to achieve these functions. The nasal vestibule is lined by vibrissae that filter large particulates as they enter the nose. The vestibule then communicates with the nasal valve region, where the nasal mucosa becomes a ciliated, pseudostratified, columnar epithelium. This type of epithelium permeates the entire sinonasal cavity; its importance is underscored when considering conditions such as Kartagener syndrome in which immotile cilia lead to chronic crusting from mucus stasis. Under the mucosa lie stromal cells, inflammatory cells, nerves, blood vessels, and seromucous glands. Each of these elements may play a role in nasal inflammation.
The nose is divided into left and right chambers by a septum comprised of cartilage and bone. Laterally, 3 bony projections—superior, middle, and inferior turbinates—project into the nasal cavity. These turbinate bones are lined by mucosa, thereby increasing the nasal surface area and covering important sinus ostia. The nasolacrimal duct drains into the inferior meatus. The frontal, maxillary, and anterior ethmoid sinuses drain into the middle meatus; the posterior ethmoid sinuses drain into the superior meatus. Finally, the sphenoid sinus ostia are superior to the choana and drain medially to the superior turbinate. Inflammation in these critical drainage sites can lead to epiphora or sinus disease.