Efficacy and safety of intradermal botulinum toxin A for post-acne erythema: a split-face randomized controlled trial.

Introduction: Post-acne erythema (PAE) is a common aesthetic sequela in patients with acne. Although numerous treatments for PAE have been investigated, the efficacy of intradermal botulinum toxin A (BTX-A) remains controversial. This study aimed to evaluate and compare the efficacy and safety of intradermal BTX-A versus broadband light (BBL) for treating PAE. Materials and methods: This study included 30 patients diagnosed with PAE at the Dermatology Outpatient Department of Henan Provincial People's Hospital in China between January 2023 and July 2023. In a split-face design, one cheek of each patient was randomly assigned to receive a single intradermal injection of BTX-A (experimental group), while the other cheek received three BBL treatments at one-month intervals (control group). The Clinician Erythema Assessment (CEA) score, VISIA results, L*a*b* values, skin physiological parameters, and adverse events were compared between the two groups. Results: The two groups showed no significant differences in baseline characteristics. At the one-month follow-up, the experimental group demonstrated significantly greater reduction in CEA, erythema index (EI), a* value, and sebum secretion compared to the control group (p < 0.05). The reduction in sebum secretion remained significantly greater in the experimental group at both the two- and three-month follow-ups (p < 0.05). Additionally, the experimental group showed a significantly greater reduction in the CEA score at 2 months and in the a* value at 3 months (p < 0.05). Compared to baseline, both groups exhibited a declining trend in EI, transepidermal water loss (TEWL), CEA score, sebum secretion, and a* value, along with an increase in skin hydration. Pain or discomfort, assessed by the visual Analog scale, was significantly higher in the experimental group (p < 0.001); however, there was no significant difference in satisfaction scores between the groups. Conclusion: In this split-face study, a single session of intradermal BTX-A was superior to a multi-session BBL regimen in reducing PAE over three months, with a comparable safety profile. These findings suggest that intradermal BTX-A is a promising and viable therapeutic option for PAE, warranting further investigation in larger, long-term studies. Clinical trial registration: The trial was registered before patient enrolment at http://www.chictr.org.cn (ChiCTR2500098527).