Objective To explore the clinical effect and mechanism of Xianhecao-Baizhu in treatment of diarrhea irritable bowel syndrome with spleen deficiency and dampness type.

Methods A total of 120 patients were randomly divided into treatment group and control group, with 60 cases in each group. The treatment group was given Xianhecao-Baizhu Decoction orally, and the control group was given pefican combined with montmorillonite powder orally. The course of treatment lasted for 1 month. The improvement of main symptoms, comprehensive efficacy, serum levels of 5-HT and IL-1β before and after treatment in two groups were observed.

Results The improvement rate of abdominal distension or abdominal pain in the treatment group was higher than that in the control group (P < 0.05). The total effective rate of the treatment group was higher than that of the control group (P < 0.05). After treatment, serum 5-hydroxytryptamine (5-HT) and interleukin -1β(IL-1β) levels were decreased in both groups, but the decrease was more obvious in the treatment group than in the control group (P < 0.05). After treatment, abdominal pain scores and diarrhea scores in the two groups decreased, and the decrease in the treatment group was more obvious than that in the control group (P < 0.05). The scores of Hamilton Anxiety Scale (HAMA) and IBS Quality of Life Scale (IBS-QOL) in the two groups after treatment were decreased compared with those before treatment, and the HAMA and IBS-QOL scores in the treatment group were lower than those in the control group (P < 0.01).

Conclusion Xianhecao-Baizhu can treat diarrhea irritable bowel syndrome with spleen deficiency and dampness type by reducing the secretion levels of 5-HT and IL-1β.