Objective To investigate the allergenicity on HPT(hygromycin B phosphotransferase) protein with BN rat model.Method Forty male BN rats were randomly divided into 4 groups(10 rats/group),ovalbumin(OVA,as the positive control),HPT protein,potato acid phosphotransferase(PAP,as the negative control),and distilled water(as the solvent control),and were daily administrated 1 ml per rat at the concentration of 1 mg/ml by gavage for 28 days.Plasma were separated on 7th day for determination of histamine.Sera were obtained on 14th day and 28th day for determination of IgE.In addition,blood pressures of rats in all groups were measured after challenging with OVA,HPT,PAP or distilled water(5 mg/ml,2 ml per rat).Results No IgE response was elicited by HPT protein,while OVA elicited strong IgE response.There was no statistical significance between HPT protein and PAP(or distilled water) in plasma histamine levels.The plasma histamine level of positive control group increased,and there was statistical significance between positive control group and HPT group.In addition,an oral challenge with OVA induced a temporary drop in blood pressure of 3 rats,while no effect was found on the blood pressure by HPT.Conclusion No allergenicity of HPT protein was found in BN rat model.