1. Department of Dermatology and Allergy, Charité– Universitätsmedizin Berlin, Germany
2. Ambulatorio di Allergologia, Clinica San Carlo, Paderno Dugnano (MI), Italy
3. Allergy Centre, Department of Dermatology, Odense University Hospital, Denmark
4. Allergy and Respiratory Diseases, DIMI – University of Genoa, Genoa, Italy
5. Department of Dermatology, Hospital del Mar, IMAS, Universitat Autònoma of Barcelona, Spain
6. Dermatology Centre, Norfolk & Norwich University Hospital, Norwich, UK
7. Department of Dermatology and Allergology, Hannover Medical University, Germany
8. Department of Dermatology, University Hospital RWTH Aachen, Germany
9. Clinical Department of Internal Diseases, Allergology and Clinical Immunology, Medical University of Silesia, Poland
10. Department of Medicine, Johns Hopkins University, Baltimore, MD, USA
11. Allergy and Immunology Department, Centro Medico‐Docente La Trinidad, Caracas, Venezuela
12. Allergy Unit, Department of Dermatology, University Hospital, Zurich, Switzerland
13. Department of Clinical Epidemiology & Biostatistics, Hamilton, Canada
14. Department of Dermatology, Johannes Gutenberg‐University, Mainz, Germany
15. Unit of Dermatology, University of Bari, Bari, Italy