IL5 and asthma: A key phenotypic characteristic that is used to define asthma subgroups is the presence or absence of biomarkers of type‐2 inflammation.4 Typical type‐2 biomarkers include bronchial epithelial gene expression of POSTN (Periostin), CLCA1 (Chloride Channel Accessory 1) and SERPINB2 (Serpin Family B Member 2),12 blood and sputum eosinophils,13 fractional exhaled nitric oxide (Feno),14 serum periostin,12, 15 serum IgE 13 and type‐2 gene expression (IL4, IL5, IL13) in sputum cells.