Nonallergic rhinitis (nAR) is characterized by mucosal inflammation with the occurrence of a minimum of two nasal symptoms such as nasal obstruction, rhinorrhea, sneezing, and/or itchy nose. These symptoms occur with no clinical endonasal infection or evidence of inhalant allergen sensitization. Nonallergic rhinitis has a wide severity range and frequently presents or is induced by hyperresponsive/nonspecific environmental causes. Nasal hyperresponsiveness is a feature of both allergic and nonallergic rhinitis. nAR involves different subgroups (Table 46.1) and is classified below. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022.