Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 10 4 2011 12 15 251 260 EN Michael P Makris Allergy Clinical Research Center, Allergy Unit, ¨Attikon¨ University Hospital, Medical School, University of Athens, Athens, Greece Christina Gratziou Asthma and Allergy Center, Evgenidion Hospital, Medical School, University of Athens, Athens, Greece Xenophon S. Aggelides Allergy Clinical Research Center, Allergy Unit, ¨Attikon¨ University Hospital, Medical School, University of Athens, Athens, Greece Sokratis P. Koulouris Allergy Clinical Research Center, Allergy Unit, ¨Attikon¨ University Hospital, Medical School, University of Athens, Athens, Greece Ioanna Koti Allergy Clinical Research Center, Allergy Unit, ¨Attikon¨ University Hospital, Medical School, University of Athens, Athens, Greece Dimitrios C Kalogeromitros Allergy Clinical Research Center, Allergy Unit, ¨Attikon¨ University Hospital, Medical School, University of Athens, Athens, Greece 2015 10 01 Allergic rhinitis and asthma share common  epidemiological features and inflammatory processes. The aim of the present study was to document the influence of natural allergen exposure in exhaled NO  (eNO)  and in spirometric parameters of patients with seasonal allergic rhinitis(SAR) and to investigate the differences among subjects with positive versus negative bronchial provocation to metacholine(BPMch). Twenty-six non-smoking  patients  (13F/13M;  mean  age 28.4ys) with  a  documented history of SAR, 15 healthy, non-atopic(6F/9M;  mean age 37.1ys) and 6 non-symptomatic atopic subjects (3F/3M; mean age 36.5ys) were studied. At the first visit during pollen season each   subject   filled  symptom-score   card,   underwent   eNO   and   nasal   NO    (nNO) measurements and spirometry. BPMch was performed within the next 10 days. At the second visit out of pollen season, all measurements but BPMch were repeated. Control subjects underwent eNO and nNO measurements.  eNO  was  significantly increased  during  pollen  season  in  BPMch   positive  vs  BPMch negative(46.22±32.60  vs 17.81±12.67, p=0.014) and  vs non-atopic  controls(11.40±5.84, p<0.001) as well as atopic controls(13.56±5.34, p=0.001). No difference was detected out of pollen season in both patients’ groups. nNO values were increased only in BPMch(+) group compared to both  control  groups in pollen season (vs non-atopics  p=0.002,   vs atopics p=0.002) and only vs non-atopics out of season, p=0.004. Regression analysis has shown that the difference in FEF25-75 values (off season-in season) is a predictor of positive BPMch. eNO  is markedly increased in BPMch  patients with allergic rhinitis while mid-expiratory flow may represent an early marker of lower airway involvement in respiratory allergy. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/317 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/317/317