1 Paediatric Allergy Unit, Hospital General Universitario Gregorio Marañón, Madrid, Spain; Gregorio Marañón Health Research Institute (IiSGM), Madrid, Spain. Electronic address: sonsoles.infante@salud.madrid.org.
2 Paediatric Allergy Unit, Hospital General Universitario Gregorio Marañón, Madrid, Spain.
3 Paediatric Allergy Unit, Hospital General Universitario Gregorio Marañón, Madrid, Spain; Gregorio Marañón Health Research Institute (IiSGM), Madrid, Spain.
4 Gregorio Marañón Health Research Institute (IiSGM), Madrid, Spain.