IGHE and asthma: Subsequently, we discovered that in asthma patients, the concentration of sphingosine metabolites in plasma and induced sputum were highly associated with clinical parameters of asthma (Fig. 1F-H) including Asthma Control Test (ACT), serum total IgE concentration, fractional exhaled nitric oxide (FENO) and index of pulmonary function FEV1/FVC (data not shown), indicating the potential impact of sphingosine metabolism on the pathogenesis of asthma.