Objective To analyze the effect of compound acid combined with doxycycline hydrochloride on skin lesion severity in patients with mild to moderate acne. Methods A total of 60 patients with mild to moderate acne diagnosed and treated in Traditional Chinese Medicine Hospital of Hepu from April 2023 to April 2024 were selected, and they were divided into the control group and the observation group by the random number table method, with 30 patients in each group. The control group was treated with doxycycline hydrochloride, and the observation group was treated with compound acid combined with doxycycline hydrochloride. The treatment effect, skin lesion severity and adverse reaction rate were compared between the two groups. Results The total effective rate of the observation group (96.67%) was higher than that of the control group (73.33%) (P<0.05). The scores of the number, type, pain and color of skin lesions in the two groups after treatment were lower than those before treatment, and those in the observation group were lower than those in the control group (P<0.05). There was no statistically significant difference in the incidence of adverse reactions between the two groups (P>0.05). Conclusion The application of compound acid combined with doxycycline hydrochloride in the treatment of patients with mild to moderate acne can effectively reduce skin lesion severity, improve related symptoms, and does not increase the incidence of adverse reactions, with good application safety.