Letter Maurits S. van Maaren*1, Dewi Rijnenberg*2, Theo H.W.M. Roovers3, Annick A.J.M. van de Ven4, Rick G. Pleijhuis4, Thomas Rustemeyer5, Paul L.A. van Daele1, Heike Rockmann-Helmbach2, Saskia M. Rombach1* both authors contributed equally1. Department of Internal Medicine, Division of Allergy and Clinical Immunology, Erasmus Medical Center, Rotterdam, the Netherlands2. Department of Dermatology and Allergology, University Medical Center Utrecht, Utrecht, The Netherlands3. Department of Allergology, Elisabeth-TweeSteden Ziekenhuis, Tilburg, Noord-Brabant, the Netherlands4. Department of Internal Medicine and Allergology, University Medical Center Groningen, Groningen, the Netherlands5. Department of Dermatology, Amsterdam University Medical Centers, Amsterdam, the Netherlands