Noninfectious, nonallergic rhinitis (NINAR): considerations on possible mechanisms

Most patients who suffer from chronic noninfectious, nonallergic rhinitis (NINAR) cannot be assigned to a syndrome of known etiology. The symptomatology may well resemble that of allergic rhinitis; however, NINAR has lower prevalence of sneezing, conjunctival symptoms, and pruritus and higher prevalence of symptoms compatible with sinus disease. The triggers for the symptoms of NINAR are mainly irritants and changes in atmospheric conditions. Among individuals who develop chronic rhinitis symptoms, the percentage of nonallergic etiology increases steadily with age and is more than 60% beyond the fifth decade of life. Our strategy regarding the pathophysiology of NINAR should be to identify functional abnormalities of nasal mucosa that can potentially result in the alleged nasal symptoms. In this respect, comparison of patients with NINAR to patients with allergic rhinitis and to healthy individuals could shed light into the cause(s) of NINAR. Three potential functional abnormalities are discussed in this article: those associated with the aging process of the nasal mucosa, those resulting in various forms of nasal hyperreactivity, and those reflecting imbalanced neuronal control of end organs of the nose. The most interesting development in the therapy of NINAR is the use of capsaicin. Although placebo-controlled studies are scarce and participants have not been adequately characterized, it is possible that abnormal nociceptor nerve endings play a role in the generation of the symptoms of NINAR. Alternatively, NINAR may represent a condition of increased perceptual acuity to irritants and to environmental changes. This problem may also benefit from defunctionalization of nociceptors.