IGHE and asthma: We observed that only butyrate supplementation significantly alleviated asthma severity, characterized by reduced cell counts (total cells and eosinophils) and type 2 cytokines (IL-4, IL-13, and IL-5) in BALF, as well as total and OVA-specific IgG1/IgE levels in serum (Supplementary Fig. 2b–g).