In a monocentric placebo-controlled double-blind study with two-period cross-over the anti-obstructive effect of azelastine nasal spray was evaluated. Nasal provocation with histamine or specific allergen respectively was performed before the pollen season in 28 patients with a history of seasonal allergic rhinitis. Efficacy was documented by rhinomanometry, acoustic rhinometry, rhinoscopy and symptom score. Acoustic rhinometry showed a statistically significant lesser decrease in nasal cavity volume in favour of azelastine after histamine provocation (p < 0.05). Reduction in nasal flow as determined by rhinomanometry confirmed this tendency (p < 0.1) after allergen provocation. The analysis of the patients’ symptom scores clearly indicated the superior efficacy of azelastine as compared to placebo, especially for nasal obstruction after provocation with both histamine (p = 0.005) and allergen (p < 0.02