The main findings of our study are that (1) higher TSLP levels are associated with increased asthma disease severity in children, and (2) children with high TSLP levels (>75th percentile) are characterized by having increased pulmonary IL-5 levels together with greater airway obstruction (FEV1/FVC % predicted) but without other characteristic phenotypical features. This evidence concerns the gene IL5 and asthma.