1. Department of Dental Materials Science; Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam; Gustav Mahlerlaan 3004 1081 LA Amsterdam The Netherlands
2. Contact Allergy Unit, Department of Dermatology; K. U. Leuven University Hospital, Kapucijnenvoer 33; 3000 Leuven Belgium
3. Department of Dermatology; University Hospital and Faculty of Medicine, University of Coimbra; Praceta Mota Pinto 3000-075 Coimbra Portugal
4. Allergy Unit, Department of Dermatology; University Hospital Basel, Spitalstrasse 26; 4031 Basel Switzerland
5. Department of Dermatology; Hospital del Mar, Universitat Autònoma; Passeig Maritim 25-29 08003 Barcelona Spain
6. Department of Biomedical Science and Human Oncology; Dermatological Clinic, University of Bari; Policlinico di Bari, Piazza Giulio Cesare 11, 70124 Bari Italy
7. Department of Occupational and Environmental Dermatology; Skåne University Hospital, Lund University, SE-20502; Malmö Sweden
8. Department of Dermatology and Allergy Centre; Odense University Hospital, University of Southern Denmark, DK-5000; Odense Denmark
9. Department of Dermatology; VU University Medical Centre; De Boelelaan 1117 1081 HV Amsterdam The Netherlands