Gut sphingolipid metabolites in infants with atopic dermatitis are associated with food allergy

Measurement of the total serum immunoglobulin E (IgE), specific IgE and eosinophil levelsThe total and specific IgE levels (IU/mL) were measured using the ImmunoCAP-CAP 1000 system (Phadia AB, Uppsala, Sweden) at 1 year of age.Concentrations of at least 0.35 kU/L (corresponding to CAP class 1) were considered positive.Atopy was defined as a ≥1 positive response.Eosinophils were counted using an automatic blood-cell counter (XE-100; Sysmex Co., Kobe, Japan) at 1 year of age. Study subjects for target lipidome analysisGut sphingolipid metabolites were prospectively analyzed from 46 healthy infants, 30 infants with only AD and 82 FA with AD in infants at 6 months of age in available fecal samples.The study population consisted of 158 six-month-old infants involved in the Cohort for Childhood Origin of Asthma and Allergic Diseases (COCOA) [1], which was a previously established general population-based birth cohort.The Institutional Review Boards (IRBs) of Asan Medical Center approved this study (IRB No. 2021-1596).A diagnosis of AD was based on the Hanifin and Rajka's criteria by pediatric allergists [2].The severity of AD was assessed using the Scoring Atopic Dermatitis (SCORAD).FA was diagnosed by a physician based on confirmed allergic sensitization, as evident by IgE levels higher than 0.35 kU/L corresponding to food antigen and history of IgE-mediated symptoms after food ingestion during the first year of life.Human feces were freeze-dried for 24 h using a benchtop manifold freeze drier and stored at -80°C until analysis.