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; Faculty of Medicine, University Hospital, 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. Parc de Salut Mar, Universitat Autònoma de Barcelona; 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 Dermatology; VU University Medical Centre; De Boelelaan 1117 1081 HV Amsterdam The Netherlands