Idiopathic rhinitis

Background: Idiopathic rhinitis (IR) can be diagnosed in case of non-allergic rhinitis after exclusion of other non-allergic rhinitis forms like drug-induced rhinitis, occupational rhinitis, hormonal rhinitis, gustatory rhinitis, and rhinitis of the elderly. The aim of the current study was to give an overview of the pathophysiological mechanisms as well as the diagnostic work-up and therapy of IR. Methods: Selective literature review in Pubmed and Medline between 1970 and 2020. Additionally, German publications not listed in the above mentioned databases were reviewed. Results: IR can be caused by inflammatory and, more often, by neurogenic mechanisms. This neurogenic inflammation, which is often accompanied by nasal hyperreactivity, seems to be triggered by a structural and functional dysregulation in the noziceptive TRPV1 substance P signaling pathway. Nasal administration of capsaicin leads to an excitation of unmyelinated sensory C fibers via TRPV1 channels resulting in a long-lasting refractory phase. During that phase, no further stimuli can activate the nerves, and symptoms of the patient decline. Discussion: Diagnosis and therapy of IR still remain challenging as simple diagnostic tools are missing and no capsaicin preparations for medical treatment have been approved for the German market. Further research on diagnosis and therapy would therefore be desirable.