Allergenic Immunotherapy and Seasonal Changes in Nitric Oxide Concentration in Exhaled Air in Seasonal Rhinitis Patients

Abstract

Concentration of nitric oxide in exhaled air (FeNO) was revealed to decrease as a result of immunotherapy. However, individuals who are exposed to environmental allergens are characterized by elevated values of FeNO. The aim of this study was to analyze the effects of subcutaneous immunotherapy (SCIT) on the dynamics of FeNO determined during consecutive pollination seasons. This study, performed between 2005 and 2008, included 41 patients with confirmed sensitivity to grass pollens and predominating symptoms of seasonal allergic rhinitis, randomly assigned to desensitization by preseasonal or maintenance SCIT. FeNO was measured prior to and during each pollen season (November-January and May-July, respectively). The results were conferred to data on grass pollination intensity in 2006-2008 (air concentration of grass pollen grains, seasonal number of days when air concentration of grass pollen reached at least 50 grains per 1 m(3)). Median content of FeNO in exhaled air was significantly higher in 2007 compared to 2006 and 2008 pollen seasons. During 2007 and 2008 pollen seasons, significant increase in FeNO was observed compared to the respective preseasonal values. Median number of days with air concentration of grass pollen ≥ 50 grains per 1 m(3) of air during 4 weeks preceding seasonal FeNO measurement was significantly higher in 2007, corresponding to higher FeNO value recorded during this pollen season. However, no significant correlation was observed between seasonal number of days with ≥ 50 grass pollen grains per 1 m(3) of air and FeNO in exhaled air (r=0.09, p=0.362). Most seasonal allergic rhinitis patients show physiological levels of FeNO prior to the pollen seasons and a marked increase in this parameter, probably proportional to pollination intensity, is observed within the seasons. ISRCTN Registry: ISRCTN86562422.