Abstract: Objective: To investigate the ameliorative effect of yeast extract on β-lactoglobulin allergy in mice and its regulatory effect on the gut microbiota, and to explore its mechanism of action. Methods: A mouse model of β-lactoglobulin allergy was established to explore the effects of yeast extract intervention on allergic symptoms, serum histamine, immunoglobulin E (IgE), and mast cell protease-1, as well as the morphology of spleen and colon tissues, intestinal microbiota, and short-chain fatty acids. Results: Yeast extract could alleviate allergic symptoms in β-lactoglobulin-allergic mice, reduce serum IgE levels, mast cell protease activity, and histamine content, improve intestinal inflammatory infiltration, increase the expression of CXCR3⁺Th1 and FOXP³⁺ Treg cells in the spleen, up-regulate the expression of Th1-type factors (IFN-γ) and Treg-type factors (TGF-β) in serum, increase the content of acetic acid, butyric acid, and short-chain fatty acids, and increase the relative abundance of Faecalibacterium, Lactobacillus, and Bifidobacterium. Conclusion: Yeast extract can alleviate food allergy induced by β-lactoglobulin, and its mechanism may be related to the regulation of intestinal microbiota, enhancement of intestinal barrier function, regulation of Th1/Treg cell immune balance, and inhibition of IgE secretion.