Breath Analysis in Asthma

Inclusion Criteria: 1. Confirmed asthma. Diagnosis of asthma is made with episodic chest symptoms and a documented reversibility of at least 12% and/or 200 ml in FEV1 after 200 ug of inhaled salbutamol or airway hyperresponsiveness in the case of normal lung function testing (PC20 methacholine \< 4mg/ml) at the time of diagnosis. 2. Age between 18 and 80 years at study entry. 3. Healthy controls: never-smokers, normal spirometry (baseline FEV1 \> 85% predicted and FEV1/FVC greater than 0.7). Exclusion Criteria: 1. Asthma exacerbation within the last 6 weeks, defined as worsening of asthma symptoms requiring a change in therapy by a physician or a change in regular asthma therapy (including short course of oral corticosteroids) 2. Any lung disease other than asthma. 3. Acute inflammatory disease (e.g. common cold) within the last 4 weeks. 4. Regular intake of oral steroids. 5. Active smoking habits / positive history of smoking. 6. Acute or chronic hepatic disease. 7. Renal failure or renal replacement therapy. 8. Pregnancy.