reduce surgical scar hypertrophy. Injecting BTxA at different time points is associated with different levels of efficacy, but the efficacy of different doses of BTxA for symptom management has not been studied. The aim of this study was to study the effect of different doses of BTxA administered early after surgery on the improvement of the sign through an experiment. The study included 22 patients who underwent surgery between September 2019 and October 2020. High and low dose BTxA were randomly administered to each half of the surgical wound immediately after surgery. Half of the subjects were injected with a low dose (4 U) of BTxA, and the other half were injected with a high dose (8 U). Symptoms were then assessed at 6 months postoperatively using the modified scar evaluation scale (mSBSES), and patient satisfaction was assessed using the visual analogue scale (VAS). The occurrence of complications or adverse events were also recorded. Twenty patients completed the study and were analyzed. Compared with the low-dose side, the high-dose sides had significantly better mSBSES scores and significantly higher VAS scores (p < 0.01, respectively). No serious adverse reactions or post-injection complications were observed. Immediately after surgery, high-dose BTxA injection (which is within the therapeutic range) improved the appearance of the postoperative scar more than low-dose injection. In patients undergoing invasive surgical procedures, cosmetic scars that appear after wound healing can cause concern. Multiple factors are associated with adverse scarring, including surgical technique, anatomical regions, skin tension, postoperative infection, and immunological responses. Early treatment of surgical wounds can result in better outcomes and reduced need for treatment at later stages. Various treatments, such as compression therapy, radiation therapy, silicone gel therapy, and laser therapy, have been shown to be helpful, but most of these therapies have been unsatisfactory. In the last ten years, several studies have shown that botulinum toxin type A (BTxA) has a positive effect on the prevention and treatment of wounds. For example, Gassner et al. reported that BTxA can regulate underlying muscle tissue to reduce wound tension during scar formation. Further, Xiao et al. confirmed that continuous injection of BTxA can reduce the thickness and amount of collagen deposition and decrease the rate of hypertrophic scarring. An early proven method of treatment to prevent scar formation is the injection of BTxA into surgical lesions at various postoperative times. In various studies, the timing of BTxA injection has been reported from immediately after surgery to 9 days after surgery. Hu et al. showed that BTxA may be more beneficial in the early stages of wound healing and that injection of BTxA immediately after wound closure may provide excellent results for facial surgical wounds. However, the effects of different doses of BTxA have not yet been studied. Therefore, this prospective, randomized, controlled, split-scar trial was conducted to investigate the effect of different doses of paralesional administration of BTxA on the appearance of the surgical scar. Go to effect of botulinum toxin injection