Glycinin, one of the main soybean antigen proteins, is researched by many nutritionists and it can cause allergic reactions in young animals.But its effect is considerably more severe in weaned piglets, showing symptoms of diarrhea.At present, in order to eliminate the allergic effects, various food processing methods were used to process soybean.However, there are few reports about the allergic reactions induced by glycinin which are alleviated with a prior immunized method in piglets.So we exploring a new way to prevent the allergic reaction induced by soybean antigen protein.The aim of this study was to investigate the effects of a prior immunization with glycinin on growth performance, serum immunoglobulin contents, small intestinal histamine release and mucosal histology in piglets.Forty piglets (7 d of age) were randomly divided into four groups of ten piglets each.Piglets of Groups Im (immunized) and Im + S (immunized and sensitized) were immunized twice by hypodermic injection with glycinin at 500 μg/kg body weight (BW) at day 7 and 21 of age.At day 23, Groups Im + S and S (sensitized) were intramuscularly injected with 2 500 μg glycinin per kg BW.The piglets of Group C (control) received a physiological saline solution by hypodermic injection.All piglets were weaned at the age of 23 d and blood samples were taken on days 7,21 and 35.At the end of the trial,five piglets per group were slaughtered and the intestine was collected for evaluating histamine levels and mucosal histology.Compared with Group C, in Group S the average daily gain (ADG) ,feed intake and gain:feed ratio were decreased (P < 0.01), and serum levels of IgG and IgE piglets were increased (P < 0.05).Furthermore, in this Group the histamine levels in the duodenum and ileum were significantly decreased (P < 0.05) , and the structure of duodenal and ileal mucosa was severely damaged.But in Groups Im and Im + S the ADG was increased (P < 0.05), serum IgE levels were decreased (P < 0.05), intestinal histamine levels were increased (P < 0.05), and the intestinal mucosa was not damaged.The results suggest that prior immunization with glycinin can increase ADG and serum IgG levels, decrease serum IgE levels and histamine release.Therefore, this method is also potentially able to protect the structural integrality of the intestinal mucosal epithelia and alleviate allergic reactions in piglets.