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).