The invention provides a lactic acid strain for resisting allergic and dermatitis reactions. The lactic acid strain is obtained by multiple chemical and physical mutagenesis of a starting strain lactobacillus acidophilus. The invention further provides a preparation for resisting allergy and dermatitis, prepared by the lactic acid strain, and the preparation is directly combined with the lactic acid strain, Bifidobacterium and Bulgarian bacteria. The lactic acid strain prepared and the preparation thereof are safe for human body and effective for colony adjustment; due to good gastric acid resistance of the lactic acid strain, the survival rate of beneficial living bacteria to the intestinal tract is high, the intestinal flora can be balanced, the immunity of the human body can be improved, and the purpose of resisting allergy and dermatitis can be achieved.