Cow's milk allergy is one of the most common food allergies in childhood. Beta-lactoglobulin (β- lg) is a dominant allergen in cow's milk. Hydrolysis is known as an effective method to reduce the allergenicity of proteins. Thus, the objective of this study was to compare the allergenicity of β-lg and its hydrolysates using an animal model. Twenty four BALB/c mice were divided into three groups and subcutaneously injected with native bovine β-lg and its hydrolysates on days 0, 7 and 14. During the sensitization period, a number of systemic anaphylactic indicators were observed in mice sensitized by β-lg compared to those sensitized by hydrolysates of β-lg. Mice sensitized by hydrolysates of β-lg showed a significantly lower spleen lymphocyte proliferation level than that sensitized by intact β-lg. Antibody levels of β-lg-specific IgE in serum induced by native β-lg were significantly high. Plasma histamine levels were also evaluated and showed the same trend as IgE. Moreover, the hydrolysates of β-lg significantly down-regulated IL-4 and IL-5 secretions in serum. These results suggested that enzymatic hydrolysis could reduce the allergenicity of β-lg.