The soybean is widely used in food industry due to its nutritional and functional qualities, but some studies have pointed it as a potent food allergen, especially in children. The concentration of IgG, IgG1 and IgE immunoglobulins in mice supplemented orally with common and transgenic soy was analysed. Mice were divided into two groups (6 animals each): lyophilized conventional soy (LCS) and lyophilized transgenic soy (LTS). Both received 100 μg of extracts for 10 consecutive days. Animals before immunization (pre-immune) formed the control group. The serum samples of the animals were undergone enzyme-linked immunosorbent assay (ELISA). The results of the ELISA tests showed that LCS and LTS induced the synthesis of specific IgG1 and IgG classes immunoglobulins and induced the formation of IgE immunoglobulin when evaluated by western blotting test. These results evidence the allergenicity of soybean and individuals with some food hypersensibility should avoid the consumption of this food.