Capsaicin for allergic rhinitis in adults

Abstract

Background: This is an update of a Cochrane Review first published in The Cochrane Library in Issue 2, 2006. Allergic rhinitis represents a global health problem. Non-specific nasal hyper-responsiveness is an important feature of allergic and non-allergic rhinitis. This phenomenon is believed to result from the effect of allergic inflammation on the sensory nerves that supply the upper airway mucosa. A pharmacological agent that has proved useful in the investigation of effects of neuronal stimulation is capsaicin, the pungent component of hot pepper. Intranasal capsaicin specifically stimulates afferent nerves consisting mostly of unmyelinated C fibers and some myelinated A-delta fibers. As a result it can trigger central and axonal reflexes, the latter being putatively mediated by the release of neuropeptides. Capsaicin, as a blocking agent of neuropeptides, blocks the axon reflex and may exert a curative effect on allergic rhinitis. Objectives: To assess the effectiveness of capsaicin for allergic rhinitis in adults. Search methods: We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; mRCT and additional sources for published and unpublished trials. The date of the most recent search was 2 September 2009. Selection criteria: Randomized controlled trials of capsaicin for allergic rhinitis in adults. Data collection and analysis: Three authors read each paper, blind to its identity. Decisions concerning inclusion were made by simple majority. We all performed quality assessment independently. Main results: One small trial did not find evidence that intranasal capsaicin had a therapeutic effect in allergic rhinitis. A small pharmacological effect on clinical histamine dose response was found. After treatment, leukotriene levels in nasal lavage did not increase in the capsaicin group. Authors' conclusions: There is insufficient evidence to assess the use of capsaicin in clinical practice.