Introduction: Bovine milk is the first and most common cause of food allergy in early childhood with a prevalence rate of about 2-7/5%. The milk coagulum consists of four proteins α_S1, α_S2, β and к-caseins. Cow's milk caseins play a basic role in persistence of cow’s milk allergy (CMA) in children. Proteolytic system of lactic acid bacteria (LAB) has the ability to hydrolyze antigenic epitopes of milk proteins and, as a result, can reduce allergy to caseins.The aim of this study was to isolate the best lactic acid bacteria strain from cow’s milk samples in order to reduce bovine milk caseins allergenicity. 
 
Materials & Methods: In the present study, after isolation of 30 cocci LAB from 20 Iranian cow’s milk samples, the effect of proteolytic activity of these bacteria on milk caseins was investigated by SDS-PAGE and RP-HPLC techniques. Subsequently, among the 15 strains with protease activity, the binding ability of native and hydrolyzed α_S1-casein to IgE sera from cow’s milk allergic patients was determined by competitive ELISA test.
 
Findings: After accomplishing biochemical tests including gram staining and catalase test, molecular identification of the strains was done by 16s rRNA fragment sequencing. The obtained results suggested that Lactococcus lactis was able to hydrolyze casein fractions in both skim milk and sodium caseinate and could reduce allergenicity of bovine milk α_S1-casein.
 
Discussion & Conclusions: Our conclusion demonstrated that the isolated Lactococcus lactis strain from cow’s milk samples can be used as a main or adjunct starter culture in dairy products to reduce immunor-eactivity of cow’s milk caseins.