Objective To investigate the effect and mechanism of Huanglian Jiedu Decoction in improving the itching symptoms of 1-chloro-2,4-dinitrobenzene(DNCB)-induced atopic dermatitis(AD)in mice.Methods Thirty-six Balb/c mice were randomly divided into normal group,model group,Dexamethasone(positive control,2.5 mg·kg-1)group and Huanglian Jiedu Decoction low-,medium-and high-dose groups(0.4,0.8 and 1.6 g·kg-1),6 mice in each group.After shaving the back of the mice,200 μL of DNCB solution was applied to the back of the mice for sensitisation(1%DNCB for 3 consecutive days)and excitation(1.5%DNCB,starting from the fourteenth day,excitation was performed once every 3 days for a total of 5 times).The stimulation and drug interventions were carried out simultaneously,and each group was administered by gavage at a set dose once daily for 14 days.The severity score of the skin lesions was calculated with reference to the Scoring Atopic Dermatitis(SCORAD),and the number of times the mice scratched within 20 minutes was recorded.The pathological changes of the lesions were observed by HE staining;mast cell infiltration was observed by toluidine blue staining;and the mRNA expression levels of thymic stromal lymphopoietin(TSLP),interleukin(IL)13,histamine H4 receptor(HRH4),and IL-31 in the lesions were detected by RT-qPCR.Results Compared with the normal group,the dorsal skin of the mice in the model group showed obvious erythema,mossification,crusting and epidermal shedding after DNCB excitation,and the severity score of the lesions was significantly increased(P＜0.001);the hyperkeratosis of epidermis,the thickness of spinous layer was significantly increased(P＜0.001),sponge oedema,and a large number of inflammatory cells infiltration was seen in the dermis;and the number of mast cells was significantly increased(P＜0.001);the times of scratches within 20 minutes was significantly increased(P＜0.01);and the mRNA expression levels of TSLP,IL-13,HRH4,and IL-31 in the skin lesion tissue were all significantly elevated(P＜0.05,P＜0.01).Compared with the model group,the skin lesions on the backs of mice in the low-,medium-and high-dose groups of Huanglian Jiedu Decoction were significantly improved,the mossy area was significantly reduced,the severity was significantly reduced,and the severity score of skin lesions was significantly reduced(P＜0.001),and the number of mast cells and the mRNA expression levels of IL-13,HRH4,and IL-31 were significantly reduced in the skin lesion tissues(P＜0.05,P＜0.01,P＜0.001);the thickness of the stratum spinosum was significantly reduced in the medium-and high-dose groups of Huanglian Jiedu Decoction(P＜0.001),and the number of inflammatory cells in the dermis was significantly reduced;the number of scratching in mice in the high-dose group of Huanglian Jiedu Decoction was significantly reduced within 20 minutes(P＜0.01),and the mRNA expression level of TSLP in the lesion tissue was significantly reduced(P＜0.05).Conclusion Huanglian Jiedu Decoction can alleviate itching symptoms in AD mice,and its mechanism of action may be related to repairing the skin barrier in AD mice,attenuating the infiltration of inflammatory cells and mast cells,and down-regulating the mRNA expressions of itch-associated factors TSLP,IL-13,IL-31 and HRH4 in skin tissues.