Background Allergic asthma is a chronic airway inflammatory disease partly characterised by high concentration of T help 2 (Th2) cytokines in bronchoalveolar lavage fluid (BALF). There is no report on the relation of peripherally circulating blood lymphocytes and asthma. We explored the balance of Th2/Th1 cytokines in asthmatic mice. Exogenous recombinant interleukin (IL) 33 acted on murine peripheral circulating blood lymphocytes, IL-5 cytokine was selected for assessing Th2 cytokines and interferon-gamma (IFN-gamma) for Th1 cytokines. Methods Female specific pathogen free BABL/c mice were sensitised by intraperitoneal injection of 20 mu g of ovalbumin emulsified in 1 mg of aluminium hydroxide gel in a total volume of 200 mu l, and challenged for 30 minutes in 7 consecutive days with an aerosol of 2 g ovalbumin in 100 ml of PBS. Then we collected BALF and isolated lymphocytes from the peripheral blood. The lymphocytes were divided into two groups: asthmatic group and normal group. Th1/Th2 cytokines was detected by enzyme-linked immunosorbent assay (ELISA) kits. Results In the asthma group, we found numerous eosinophils and lymphocytes on the glass slides. We then confirmed that the optimal concentration of IL-33 was 10 ng/ml and time of IL-33 stimulating lymphocytes was 24 hours. In the asthma group, the production of IL-5 was significantly increased over normal group after stimulation with IL-33 (P<0.05) and the production of IFN gamma was supressed from IL-33 stimulated lymphocytes (P<0.05). Conclusion IL-33 acts on lymphocytes of peripheral blood increasing secretion of Th2 cytokines and inhibiting secretion of Th1 cytokines.