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.