1 Allergy Unit, Department of Dermatology, University Hospital, Zurich, Switzerland; Center of Dermatology and Allergology, Luzerner Kantonsspital, Lucerne, Switzerland. Electronic address: barbara.ballmer@luks.ch.
2 Department of Paediatric Pneumology and Immunology, Charité Universitätsmedizin Berlin, University Medical Center, Berlin, Germany.