The study group will consist of patients referred for methacholine challenge test. All patient will undergo spirometric, plethysmographic, interrupter technique and FOT examinations - before and after inhalation of aerosols. Patients will also undergo the measurement of nitric oxide concentration in exhaled air and laboratory tests, including: blood count, measurement of serum C-reactive protein, sodium, potassium, creatinine, immunoglobulin E and N-Terminal pro-brain natriuretic peptide (NT-proBNP) concentration.