In recent years, periostin as measured in serum or plasma, has emerged as a biomarker of type-2 inflammation in asthma due to its marked up-regulation by IL-13 in airway epithelial cells and fibroblasts [1, 2], alongside significant relationships with other surrogate markers of type-2 inflammation including blood and sputum eosinophils and exhaled nitric oxide [3]. This evidence concerns the gene IL13 and asthma.