The prevalence of obesity is increasing in Brazil, generating high costs for the health system. In the search for alternative therapies to control the obesity, several researches seek active compounds in natural products in order to find better pharmacological effects. Inhibitors of α-amylase such as phaseolamine extracted from common beans (Phaseolus vulgaris) have shown satisfactory results in weight loss. The present study aimed to verify the possibility of phaseolamine-causing allergic reactions through the humoral response in mice sensitized with phaseolamine. Swiss female mice (n = 10) were sensitized orally with 100 µg of lyophilized phaseolamine diluted in water for 10 consecutive days and reinforced on the 21th and 35th days after the beginning of this experiment. The production of immunoglobulins IgG, IgG1 and IgE was measured by ELISA and western blotting. The immunological response was investigated and it was found that phaseolamine induced the synthesis of IgG and did not induce the synthesis of IgG1 and IgE. The present study indicates that the product did not cause allergic reactions.