Eosinophils are recognized as a cell type important in asthma exacerbation pathogenesis, as higher levels of eosinophil cationic protein (ECP) concentrations in sputum in asthma exacerbations were associated with a longer hospital stays,36 and treatments reducing eosinophil numbers in asthma, such as anti‐IL‐5 therapeutics mepolizumab and benralizumab have been shown to reduce exacerbation frequency.37, 38. This evidence concerns the gene IL5 and asthma.