title: Reply.
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Klaus
authors.initials: K
authors.lastname: Bønnelykke
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Nadja Hawwa
authors.initials: NH
authors.lastname: Vissing
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Astrid
authors.initials: A
authors.lastname: Sevelsted
authors.affiliation: Airway Disease Infection Section, MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, National Heart & Lung Institute, Imperial College London, London, United Kingdom; Centre for Respiratory Infection, National Heart & Lung Institute, Imperial College London, London, United Kingdom.
authors.forename: Sebastian L
authors.initials: SL
authors.lastname: Johnston
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark. Electronic address: bisgaard@copsac.com.
authors.forename: Hans
authors.initials: H
authors.lastname: Bisgaard