Mechanisms of rhinitis

The differential diagnosis of rhinitis is broad. New concepts of lymphocyte subsets and cytokine production permit speculation about new disease classifications. For allergic rhinitis, mast cell degranulation is the major defining feature. Histamine remains preeminent for inducing the symptoms of allergic rhinitis, including itching, sneezing, dripping, and congestion. Histamine, however, is joined by a growing list of immediate and late-phase mediators that plague the muscosal surface. The mechanisms of symptom production in rhinitis are reviewed, focusing on the effects on mucosal resident cells, such as epithelium, endothelium, and glands, the role of nociceptive and parasympathetic nerves, and the recruitment and activation of leukocytes in the mucosa. The benefits and mechanisms of action of antihistamines, anticholinergic agents, and glucocorticoids are discussed.