1. Department of Internal Medicine, University Hospital Basel, Switzerland
2. Department of General Practice and Health Services Research, University of Zurich, Switzerland
3. Division of Immunology and Allergy, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
4. Allergology, University Hospital Basel, Switzerland
5. Allergology and Clinical Immunology, University Hospital Bern, Switzerland
6. Department of Respiratory Medicine, University Hospital Basel, Switzerland