Nitric oxide metabolites in allergic rhinitis: The effect of pollen allergen exposure.

BACKGROUND Seasonal allergic rhinitis (SAR) is characterised by an inflammation consequent to allergen exposure. Nitric oxide may be involved in allergic inflammation. OBJECTIVE This study evaluated the serum nitrite concentrations in SAR patients during and outside pollen exposure in order to estimate activity of nitric oxide synthases. METHODS One hundred and two (56 females, 46 males, median age: 28.7 years) were included in this study: 56 with SAR evaluated outside the pollen season and so without allergic inflammation and symptoms, and 46 with SAR evaluated during the pollen season with symptoms. Serum concentrations of nitrite were measured and in those patients exposed to pollens, results were compared to scores of the Visual Analogue Scale for nasal obstruction perception. RESULTS Serum nitrite concentrations were higher in SAR patients evaluated outside the pollen season (U=-6.78; p<0.0001), moreover, there was a significant relationship between nasal obstruction perception and nitrite in patients evaluated during the pollen season. CONCLUSION This preliminary study demonstrates that serum nitric oxide metabolism depends on allergen exposure.