Background: Nitric oxide (NO) plays a major role in the regulation of vascular tone and in non-specific host defence. The epithelium in the paranasal sinuses was recently identified as the major site of NO production in the upper airways.
Objective: To investigate NO status in allergic rhinitis, we compared the NO concentration in the nasal cavities of control subjects (n = 19) and in patients with allergic rhinitis (n = 36) with symptoms (WS, n = 17) or without symptoms (WOS, n = 19) on the day of the test.
Methods: NO concentration was measured using a chemiluminescent analyser aspiring from each nasal cavity at a sampling flow rate of 0.7 L/min, before and 10 min after administration of a nasal vasoconstrictor.
Results: The mean NO concentration (+/- SE) in the control was 235 +/- 11 ppb and 225 +/- 9 ppb in the right and left nostrils respectively, and was decreased by 14% and 12% by the nasal vasoconstrictor (P < 0.001). The NO concentration in patients with allergic rhinitis was significantly higher in the right and left nostrils (382 +/- 20 ppb and 396 +/- 28 respectively, P < 0.0001 versus control). All WOS patients demonstrated normal or increased NO concentrations in both nostrils, whereas two WS patients showed decreased NO concentrations in the left nostril. Inhalation of a nasal vasoconstrictor increased NO concentration by 6% and 27% in the right and left nostrils respectively in WS patients.
Conclusion: Nasal NO concentration is increased in patients with allergic rhinitis. Interestingly, patients without symptoms on the day of the test also showed a clear-cut increase in nasal NO production, which could reflect a permanent inflammation of the sinus mucosa.