1. Department of Dermatology and Allergy, Herlev and Gentofte Hospital, Gentofte Hospitalsvej 15, 2900 Hellerup, University of Copenhagen , Denmark
2. Department of Dermatology and Venereology, Bispebjerg and Frederiksberg Hospital, University of Copenhagen , Denmark
3. Section of Epidemiology, Department of Public Health, University of Copenhagen , Denmark
4. Department of Clinical Medicine, University of Copenhagen , Copenhagen , Denmark