Intradermal injection of botulinum toxin for erythema in rosacea: A scoping review and meta-analysis

Background Rosacea is a skin condition characterised by persistent facial erythema, flushing, papules, pustules, and telangiectasia. Botulinum toxin A (BoNT-A) has been used to treat a variety of conditions, but its effectiveness in improving facial erythema in rosacea patients is uncertain. Objectives The aim of the study is to evaluate the effectiveness and determine the optimal dose of BoNT-A treatment for rosacea. Methods An online database search (Pubmed, Cochrane Library and Embase) was conducted on 30th June 2023 to identify studies that used intradermal injection of BoNT-A to treat facial erythema in rosacea patients and excluded studies in which BoNT-A was used for facial erythema due to other known medical condition such as menopause, drug or pregnancy. The primary outcome measure for this study was the improvement in erythema score as objectively assessed. A random effect model was used in the meta-analysis. Results Seven studies involving a total of 167 rosacea patients were included in the meta-analysis. Meta-analysis of two randomised controlled trials showed improvement of erythema on the third month after treatment standardized mean difference (SMD): 1.676, 95% confidence interval (CI): 2.278-1.074, I2: 35.76%). A separate analysis of seven single-armed treatment studies found significant improvement in erythema with intradermal injection of BoNT-A at one, two and three months after treatment (first month: SMD: 2.712, 95% CI: 4.1182-1.243; second month: SMD:2.213, 95% CI: 3.702-0.725; third month: SMD: 1.912, 95% CI: 2.882-0.941). Adverse events, including mild facial paralysis and injectional purpura, were reported in some studies. Limitation The limitations of this study include heterogeneity in study design and a small sample size. Conclusion Intradermal injection of BoNT-A may be an effective treatment for facial erythema in rosacea. Unwanted facial muscle paralysis was seen in different BoNT-A concentration but not noted when the dose was less than 0.02ml per site. Future studies particularly randomised trials are required to identify the volume of injection required to reduce the erythema.