Objective: To observe the effect of Xixin oil on blood histamine content and pathomorphological change in nasal mucosa of guinea pigs with allergic rhinitis (AR). Method: Forty FMMU guinea pigs were randomly divided into control group,AR model group,Xinqin granule group and Xixin oil group,with 10 cases in each group.Generally sensitized guinea pigs were received repeated local sensitization in nasal cavity with ovalbumin.Guinea pigs in control group and model group were given normal saline,while guinea pigs in Xinqin granule group were given 4.65 g ·kg^-1 Xinqin granule and 0.45 g ·kg^-1volatile oil for Xixin oil group.Pathomorphological changes in nasal mucosa were observed and blood histamine was determined for each group. Result: Xixin oil could significantly reduce the amount of nasal secretions,sneezing and the degree of nasal scratching of AR guinea pigs.The degree of nasal mucosal inflammation in Xixin oil group was improved and the content of histamine was decreased obviously. Conclusion: Xixin oil can alleviate local symptoms and improve the degree of inflammation after local invasion in nasal mucosal of guinea pigs with AR.The possible mechanism might be related with inhibition of histamine release,which play an important role in the treatment of allergic rhinitis.