Orally exhaled nitric oxide in patients with seasonal allergic rhinitis during natural pollen season.

BACKGROUND: Nitric oxide (NO) is the endogenous molecule involved in regulatory, protective, and defensive mechanisms. Although exhaled NO (ENO) has been used to monitor patients with asthma, possible usage of ENO in allergic rhinitis (AR) still needs to be evaluated. The authors wanted to determine the levels of NO exhaled orally both out of the pollen season and during the natural pollen exposure in patients with AR without asthma.

METHODS: Forty-six patients without asthma, with seasonal AR (SAR) and 15 healthy, nonreactive, nonatopic subjects as a control group were investigated. ENO, congestion score, and peak nasal inspiratory flows (PNIFs) were measured in all subjects 6 weeks before the pollen season, at the height of the pollen season, and 6 weeks after the end of the pollen season.

RESULTS: Patients with SAR had significantly higher basal ENO values compared with healthy control. The number of parts of NO increased in both groups during the pollen season but only in AR patients was the increase significant compared with the levels before the pollen season. Those with SAR and high levels of NO in exhaled air at the height of the pollen season had significantly lower PNIF rates and higher obstruction scores than out of the pollen season and in the healthy group.

CONCLUSION: Natural exposure may lead to an elevation of ENO in the patients with SAR without asthma. We estimate that the increased ENO may result from subclinical allergic inflammation present within the lower airways of nonasthmatic patients with SAR.