1 Department of Internal Medicine, Section of Allergology, Erasmus MC, Rotterdam, The Netherlands.
2 Department of Pediatric Respiratory Medicine and Allergy, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
3 Department of Allergy, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
4 Department of Pediatric Respiratory Medicine and Allergy, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: b.j.vlieg-boerstra@amc.uva.nl.