Objective To explore the effect of Qufeng Xiaodian decoction on rash symptoms and immune function in children with allergic purpura. Methods A total of 50 children with allergic purpura admitted to Yanchang County People's Hospital from February 2020 to February 2024 were selected as the research objects. They were divided into control group and observation group by random number table method, with 25 children in each group. The control group was treated with conventional western medicine, and the observation group was treated with Qufeng Xiaodian decoction on the basis of the control group. The clinical efficacy, rash symptom score, immune function index, clinical symptom regression time, hospitalization time and adverse reactions were compared between the two groups. Results The total effective rate of treatment in the observation group was 92.00%, which was higher than 80.00% in the control group (P <0.05). The rash symptom score of the two groups after treatment was lower than that before treatment, and that of the observation group was lower than that of the control group (P <0.05). After treatment, IgA, IgM and IgG in the two groups were lower than those before treatment, and those in the observation group were lower than those in the control group (P <0.05). The disappearance time of pruritus and purple spot and hospitalization time in the observation group were shorter than those in the control group (P <0.05). The incidence of adverse reactions in the observation group was 8.00%, which was lower than 12.00% in the control group (P <0.05). Conclusion Qufeng Xiaodian decoction is effective in the treatment of children with allergic purpura, which can effectively reduce rash symptoms, regulate immune function, promote the disappearance of clinical symptoms, shorten hospitalization time, improve treatment effect, and has fewer adverse reactions. It is worthy of clinical application.