IGHE and allergic asthma: Between 2014 and 2020, the ERS/ATS severe asthma guidelines newly recommended that the T2 biomarkers of blood eosinophils ≥ 260 cells/μL and FeNO ≥ 19.5 ppb can be used to identify adults with severe allergic asthma likely to benefit from anti-IgE therapy (alongside total IgE level) [3].