Pathological scarring, i.e. hypertrophic scars and keloids, can be reduced by injecting botulinum toxin A, according to the latest studies. The effect of improving the appearance of scars here underlies the theory of chemoimmobilization.
The musculature surrounding the wounds tends to become hyperactive as a result of microtrauma and, accordingly, the inflammatory phase is increased and prolonged, with cytokines and growth factors being released.
The injection of botulinum toxin A into the muscles surrounding the wound causes the neurotoxin to now paralyze this muscle in a dose-dependent manner. This inhibits the growth of fibroblasts and thus the formation of scars.
In order to determine the exact dosing of botulinum toxin A, Chen et al. (2021) investigated the influence of different doses on surgical scars in a randomized study with 24 participants of different genders in middle age. For this purpose, the drug was injected intradermally into scars after tumour excisions without muscle involvement.
Here, different doses were injected into each half of the surgical wound closure following surgery. On the one hand a lower dose with 4 Botox units per injection point at a distance of one centimeter and on the other hand a higher dose with 8 Botox units per injection point.
The result of this study showed significantly better mSBSES scores and VAS scores in the scar half with the higher botulinum toxin dosage than the other half with the lower dosage.
Thus, it can be concluded that immediate injection of botulinum toxin A can improve the appearance of surgical scars, although it should be noted that a uniform treatment regimen should not be used due to differences in tissue composition and other individual factors.
A major disadvantage of botulinum toxin A injections in scars is only the high cost and the lack of evidence whether the preparation is also effective in keloids.