Objective To observe the ultrastructure changes of nasal mucosa cilia in rat models of allergic rhinitis (AR), and the effect of 18β-glycyrrhetinic acid on the pathological changes of nasal mucosa cilia. Methods Totally 96 Wistar rats were randomly divided into 4 groups: normal control group, AR model group, loratadine treatment group and glycyrrhetinic acid treatment group.AR models were established by ovalbumin-induction, and then each group was administered with corresponding treatments. At 2 weeks, 4 weeks, 6 weeks, and 10 weeks after treatment, the behavioral changes were compared between different groups and the ultrastructure changes of nasal mucosa cilia were observed under scanning electron microscope and transmission electron microscope in each group. Results Model group developed typical AR symptoms: the cilia in the top layer of the nasal mucosa were disordered, lodging, matted together and some were even lost; the cilia membrane was broken, and the microtubules of cilia were reduced or disappeared; furthermore, small and abnormal cilia were observed, while mucous blanket on the top of cilia was thickened and contained neutrophils, monocytes, eosinophils and other inflammatory cells; and with persistent allergen exposure, the morphological changes of the nasal mucosa cilia aggravated gradually. While in both glycyrrhetinic acid treatment group and loratadine treatment group, the AR symptoms were relieved gradually, and the morphological damages of nasal mucosa were gradually recovered: the cilia were well arranged with the density similar to that of normal group, and small cilia were reduced and the thickened mucous blanket on the top of cilia disappeared. Conclusion Persistent exposure to allergen can lead to progressive ultrastructure damages to nasal mucosa cilia in rat AR model, and 18β-glycyrrhetinic acid can, to some extent, relieve or even reverse the ultrastructure changes of nasal mucosa cilia.