IL4 and asthma: A correct definition of asthma and CRS phenotype/endotype is crucial, taking into account the availability of novel biological therapies, such as anti-IgE, anti-IL-5/IL-5Rα and anti-IL4/IL-13Rα, which are dedicated to patients who do not respond to conventional asthma or CRSwNP therapies [21,22,23,24].