Local Allergic Rhinitis: A Different Rhinitis Endotype? Literature Overview

Featured Application: Although there are different rhinitis phenotypes and—due to recent research and the spread of knowledge on the physiopathological mechanisms underlying rhinitis—different rhinitis endotypes have been recognized, the differences between them are not always clear. This review focused on the features of local allergic rhinitis (LAR) as a rhinitis endotype independent of allergic rhinitis (AR) and nonallergic rhinitis (NAR). Chronic rhinitis (CR) is commonly divided into allergic rhinitis (AR) and nonallergic rhinitis (NAR). AR is triggered by the immunoglobulin E (IgE)-mediated response to allergens, whereas NAR is characterized by the absence of allergic sensitization. Previous studies have demonstrated the presence of local IgE in the nasal mucosa of patients suffering from typical allergic rhinitis (AR) symptoms but without a history of atopy and a positive response to a nasal allergen challenge (NAC). This condition was recently defined as local allergic rhinitis (LAR), which is supposed to be a different CR characterized by a type 2 (T2) inflammation response with the release of typical T2 mediators. LAR is defined as a phenotype of AR characterized by a localized nasal allergic response that is negative skin prick testing to allergens in the absence of serum-specific IgE. Diagnosis is based on a positive response to NAC. This review is an update of LAR literature, focusing on the definition of LAR as an independent endotype. LAR, AR, and NAR are characterized by the same clinical symptoms, although there are some differences between these three subtypes. However, the literature data are not yet univocal in defining LAR as an independent endotype.