The aim of the present study was to investigate the effect of oral probiotic bacteria administration at different times on ovalbumin-sensitized rats. Brown-Norway (BN) rats were orally sensitized with ovalbumin for 6 weeks. Probiotics were administered before the initial sensitization (prevention group) or at the end of sensitization period (treatment group). In whole-course intervention group, probiotics were administered 2 weeks before the initial sensitization until 1 week after the end of sensitization period. Ovalbumin-immunoglobulin E (IgE) level, intestinal barrier function and immune responses were analyzed. The positive control group had a significantly increased ovalbumin-IgE level (P<0.05), impaired intestinal barrier function and skewed T-helper 1 (Th1)/Th2 cytokine balance compared with the negative control group. In probiotics prevention and whole-course intervention groups, the infiltration of inflammatory cells (eosinophil and mast cells) in small intestinal mucosa was significantly lower (P<0.05), and the ratio of cytokine interferon-γ/interleukin-4 produced by spleen and mesenteric lymph nodes significantly higher (P<0.05) than in the positive control group, which suggested a cytokine profile inclined to Th1. Both probiotics prevention and prebiotics treatment could attenuate food allergic response. Probiotics prevention tends to modulate the immune response, whereas probiotics treatment has a more obvious effect in enhancing intestinal integrity.