Background: A link (''naso-bronchial reflex'') between nasal and bronchial reactivity seems to exist. The effect of nonspecific nasal challenge (standing for the exposure to irritative stimuli at the workplace) on lung function indices and nonspecific bronchial reactivity is not known. Methods: In 80 healthy workers (age: 36.0 Ϯ 8.6 years) continuously exposed to acceptable levels of different respiratory irritants (for more than 2 years) nasal challenge was performed by spraying doubling concentrations of histamine (0.0625-16.0 mg/mL, doses of histamine: 7.8 g-2.08 mg) into each nostril. Before and immediately after nasal challenge spirometry and the bronchoprovocation test with histamine (0.5-128 mg/mL) was performed. Results: Although nasal challenge with histamine had not reduced airway caliber (before nasal challenge vs. following nasal challenge: FEV 1 3.8 Ϯ 0.8 vs. 3.7 Ϯ 0.8 L, and MEF 50 4.3 Ϯ 1.4 vs. 4.3 Ϯ 1.4 L/s, mean Ϯ SD, respectively), it had significantly reduced nonspecific bronchial reactivity in 30.2% of the irritant-exposed subjects. Conclusions: Nasal challenge with histamine decreases nonspecific bronchial reactivity in workers occupationally exposed to respiratory irritants. Thus, a methodological implication would be that these two tests should not be performed consecutively in less than 2 hr in the same subjects.