Objective To investigate the effect of Xiaofenghuoxue decotion(XFHX)on the production of Th1 and Th2 cytokine in bronchoalveolar lavage fluid(BALF)in asthma guinea pigs sensitized and challenged with ovalbumin.Methods The animals were randomly divided into 5 groups:the normal control group,the asthma group,the XFHX high dose group,the XFHX low dose group and the budesonide group.2 weeks after sensitization with a mixture of 10% OVA and 10% Al(OH)3,the drugs were given to the animals for 7 days,and then the animals were challenged with aerosol of 1% ovalbumin,the latency time for the onset of respiratory abnormalities was examined,BALF was collected 16 h after.Leukocyte in BALF was counted.The level of IFN-γ reduced by Th1 cells and IL-4 and IL-5 produced by Th2 cells were determined by EILSA.NO contents were also examined.Results The latency time for the onset of respiratory abnormalities and leukocyte infiltration in both XFHX high dose group and low dose group significantly decreased compared with the asthma group.The level of IFN-γ in both XFHX high dose group and low dose group significantly increased compared with the asthma group,the level of IL-4 and IL-5 in both XFHX high dose group and low dose group significantly decreased compared with the asthma group.The production of NO was inhibited in both XFHX high dose group and low dose group compared with the asthma group.Conclusions These results suggest that the anti-asthma effect of Xiaofenghuoxue decotion is associated with NO regulated reversal of Th1/Th2 cytokine balance in allergen-induced asthma guinea pigs. Objective To investigate the effect of Xiaofenghuoxue decotion(XFHX) on the production of Th1 and Th2 cytokines in bronchoalveolar lavage fluid(BALF)in asthma guinea pigs sensitized and challenged with ovalbumin.Methods The animals were randomly divided into 5 groups: the normal control group ,The asthma group,the XFHX high dose group,the XFHX low dose group and the budesonide group.2 weeks after sensitization with a mixture of 10% OVA and 10% Al(OH)3,the drugs were given to the animals for 7 Days,and then the animals were challenged with aerosol of 1% ovalbumin,the latency time for the onset of respiratory abnormalities was examined,BALF was collected 16 h after.Leukocyte in BALF was counted.The level of IFN-γ reduced by Th1 cells And IL-4 and IL-5 produced by Th2 cells were determined by EILSA.NO contents were also examined.Results The latency time for the onset of respiratory abnormalities and leukocyte infiltration in both XFHX high dose group and low dose group slightly decrease d compared with the asthma group.The level of IFN-γ in both XFHX high dose group and low dose group significantly increased compared with the asthma group,the level of IL-4 and IL-5 in both XFHX high dose group and low dose Group significantly decreased compared with the asthma group.The production of NO was inhibited in both XFHX high dose group and low dose group compared with the asthma group.Conclusions These results suggest that the anti-asthma effect of Xiaofenghuoxue decotion is associated with NO regulated reversal Of Th1/Th2 cytokine balance in allergen-induced asthma guinea pigs.