Abstract: Su Hong, Yang Zhi, Tan Yaxin, Shi Hang, Chen Yuan, Jiang Song, Zhang Yiqiong, Xiong Ying, He Li Department of Dermatology and Venereology, First Affiliated Hospital of Kunming Medical University, Kunming 650032, China （Su H, Yang Z, Tan YX, Shi H, Jiang S, Zhang YQ, Xiong Y, He L）; Department of Dermatology and Venereology, First People′s Hospital of Yunnan Province （Chen Y） Corresponding author: Yang Zhi, Email: vipyz@126.com 【Abstract】 Objective To evaluate and compare the clinical efficacy and safety of intense pulsed light （IPL） versus 595?nm pulsed dye laser （PDL） for the treatment of post?acne erythema. Methods A randomized split?face clinical trial was conducted. A total of 20 patients with post?acne erythema were enrolled, and randomized to receive treatment with IPL on one half of the face and 595?nm PDL on the other facial side once every 4 weeks for 3 sessions. Digital photographs were taken using the VISIA, and erythema index was recorded before each treatment and one month after the last treatment. The severity of bilateral facial erythema was evaluated based on a 4?point grading scale before the first treatment and after the last treatment. Pain scores and adverse reactions were recorded using a visual analogue scale （VAS） after each treatment, and a patient satisfaction survey was conducted by questionnaire at the last follow?up. Results The mean erythema index on the IPL side before and after treatment was 472.25 ± 86.02 and 357.15 ± 82.71 respectively, and that on the PDL side before and after treatment was 476.40 ± 74.25 and 360.05 ± 64.83 respectively. Repeated measures analysis of variance （ANOVA） showed that the erythema indices on both treated sides signi?cantly decreased over time （F = 197.666, P < 0.001）, and the efficacy of IPL was better than that of PDL （F = 1 173.909, P < 0.001）. Erythema severity grades on the IPL side as well as on the PDL side significantly differed between before and after treatment （Z = 28.735, 31.450, respectively, both P < 0.001）. As VAS showed, the pain score on the PDL side was significantly lower than that on the IPL side （t = 2.468, P < 0.05）. Among the 20 patients, 17 and 15 assessed their improvement as good or excellent after PDL and IPL treatment respectively, but there was no significant difference between the two groups （Z = 2.696, P > 0.05）. The adverse reactions included erythema, burning sensation, tense sensation, blistering and hyperpigmentation on IPL?treated side, and erythema and purpuric reactions on the PDL?treated side, which all disappeared in a few hours to several days. Conclusions Both IPL and 595?nm PDL are effective and safe for the treatment of post?acne erythema, and are worthy of clinical promotion and application. IPL shows superiority in the efficacy, but elicits higher pain sensation compared with PDL.