 All patients are recruited at the outpatient clinic of Allergology and Clinical Immunology of the University Hospital of Bern, Switzerland. Patients older than 18 years and younger than 65 years of age with clinically well-controlled asthma under a fixed combination of budesonide formoterol or equivalent are included after having signed an informed consent form. Clinically well-controlled asthma is defined as the absence of symptoms and exacerbations during the 8 weeks prior to inclusion. In addition, documented airway hyperresponsiveness to mannitol and methacholine as well as current non-smoker status is required for inclusion. Smokers, women planning a pregnancy or pregnant, and patients with any significant illness that can interfere with the feasibility or the results of the provocation tests, such as acute asthma or severe cardiovascular disease, will not be included. 