1. Department of Dermato-Allergology; National Allergy Research Centre, Gentofte Hospital, University of Copenhagen; 2900 Hellerup Denmark
2. Occupational Medicine; Finnish Institute of Occupational Health; 00250 Helsinki Finland
3. Department of Dermatology; Bispebjerg Hospital, University of Copenhagen; 2400 Copenhagen Denmark
4. Department of Dermatology and Allergy Centre; Odense University Hospital, University of Southern Denmark; 5000 Odense Denmark
5. Allergy Unit, Department of Dermatology; University Hospital and University of Basel; 4031 Basel Switzerland
6. Department of Occupational and Environmental Dermatology; Skåne University Hospital, Lund University; SE-20502 Malmö Sweden
7. Hospital Municipal de Vicente López ‘Profesor Bernard Houssay’; Buenos Aires Argentina
8. Department of Dermatology; Hospital del Mar, Universitat Autónoma de Barcelona; 08003 Barcelona Spain
9. Department of Dermatology; University Hospital and Faculty of Medicine, University of Coimbra; 3000-075 Coimbra Portugal
10. Contact Allergy Unit, Department of Dermatology; University Hospital K. U. Leuven; B-3000 Leuven Belgium
11. Department of Dermatology, Environmental Medicine, Health Theory; University of Osnabrueck; D-49069 Osnabrueck Germany
12. Institute of Environmental Medicine, Karolinska Institutet; SE-17177 Stockholm Sweden
13. Department of Dermatology; University Hospital Örebro; SE-70185 Örebro Sweden
14. Allergy Unit, Department of Dermatology; University Hospital Erlangen; 91054 Erlangen Germany
15. Unit of Occupational and Environmental Dermatology; Centre for Occupational and Environmental Medicine, SLSO; SE-11365 Stockholm Sweden
16. Department of Dermatology; VU University Medical Centre; 1081 HV Amsterdam The Netherlands
17. Department of Experimental Dermatology and Cosmetology; Jagiellonian University Medical College; 30-688 Krakow Poland
18. Department of Dermatology; CHRU Besançon; 25030 Besançon Cedex France
19. Department of Cutaneous Allergy; St John's Institute of Dermatology, St Thomas' Hospital; London SE1 7EH UK
20. Spire Hospital; Leeds LS8 1NT UK
21. Department of Medical Informatics, Biometry and Epidemiology; University of Erlangen/Nürnberg; 91054 Erlangen Germany