Intranasal capsaicin in management of nonallergic (vasomotor) rhinitis.

Capsaicin is a selective transient receptor potential vanilloid 1 (TRPV1) ion channel agonist and has been demonstrated to reduce nerve conduction of nociceptive C fibers in the trigeminal nerve without affecting conduction in Adelta fibers. This chapter reviews the classification of chronic rhinitis subtypes, the prevalence and epidemiology of nonallergic rhinitis (NAR), postulated pathophysiology and mechanisms of NAR including the role of transient receptor potential (TRP) ion channels and discusses the potential therapeutic benefits of capsaicin in the treatment of chronic rhinitis subtypes, specifically NAR. Evidence supports that hypersensitivity of TRP ion channels on sensory afferent neurons innervating nasal mucosa is responsible for inducing NAR symptoms. These symptoms, characterized as excessive nasal glandular secretion, nasal congestion, and headache, are mediated through neuropeptide release during axonal and parasympathetic reflexes which are initiated by a spectrum of nonspecific irritants that activate TRP channels. Rational approaches to treat the pathophysiology of NAR would be to develop therapies with selective TRPV1 agonist activity like capsaicin that target desensitization of TRP ion channels on sensory afferent nerves.