1. Department of Dermatology, Inselspital; Bern University Hospital; Bern Switzerland
2. Centro Studio, Italian Group for Epidemiological Research in Dermatology (GISED); Bergamo Italy
3. Graduate School for Cellular and Biomedical Sciences; University of Bern; Bern Switzerland
4. Department of Dermatology; University Hospital Zurich; Zurich Switzerland
5. Faculty of Medicine; University of Zurich; Zurich Switzerland
6. Allergy Unit, Clinic of Dermatology and Allergology; Cantonal Hospital St Gallen; St. Gallen Switzerland
7. Department of Dermatology; University Hospital of Lausanne CHUV; Lausanne Switzerland
8. Department of Dermatology; University Hospital Basel; Basel Switzerland
9. Clinic of Dermatology and Allergology; Cantonal Hospital St Gallen; St Gallen Switzerland
10. Hautärzte am Graben; Winterthur Switzerland
11. Department of Dermatology; Cantonal Hospital Aarau; Aarau Switzerland
12. Department of Dermatology; Geneva University Hospitals (HUG); Geneva Switzerland
13. Dermatology Office; Versoix Switzerland
14. Department of Clinical Social Medicine, Occupational and Environmental Dermatology; University Hospital, Ruprecht Karls University; Heidelberg Germany
15. Institute of Epidemiology and Preventive Medicine; University of Regensburg; Regensburg Germany
16. Department of Dermatology; San Bortolo Hospital; Vicenza Italy