There is also increasing evidence that BoNTA can elicit biological effects beyond muscular relaxation, which may include direct effects within the skin.7 Hence, there could be many potential applications in dermatology. BoNTA formulations are already indicated for the treatment of axillary hyperhidrosis via anticholinergic effects on the sweat glands, based on intradermal rather than intramuscular injection.1,2,8 In addition, there are reports of BoNTA usage in the management of various other dermatological conditions, including alopecia, psoriasis, pigmentation disorders, and cutaneous vascular conditions.7,9
Furthermore, there is a growing body of data showing that BoNTA injections can reduce scarring, for example following surgery.6,10,11 Although the mechanisms of effect may include the prevention of underlying muscle contraction (thereby reducing wound tension),6 direct effects on wound healing have also been proposed.7
For the past few years, I have been injecting BoNTA intradermally as an ‘adjuvant’ treatment to reduce scarring in selected patients undergoing minor dermatological surgeries such as the excision of sebaceous cysts or intradermal naevi. These are common procedures that are often associated with troublesome scarring. However, to the best of my knowledge, there are no previous descriptions in the literature of adjuvant BoNTA injection in these settings.
Personal interest in using BoNTA to aid wound healing after sebaceous cyst excision was first stimulated by a procedure on a patient’s forehead. OnabotulinumtoxinA was injected into the frontalis muscle at the time of treatment to reduce tension on the sutures. It was also injected into the wound edges based on an analogy with hyperhidrosis – that if BoNTA can reduce sweating,8,12 it might also reduce sebaceous secretions. Indeed, a recent systematic review described several studies showing that BoNTA can reduce sebum production and excretion.13 In this particular instance, the excision wound healed particularly rapidly and well, with minimal scarring.
Subsequent repeats of this procedure have also been successful. For example, Figure 1 shows a patient with a recurrent sebaceous cyst that had first been removed around 1 year previously. The cyst was highly adherent, and excision was difficult. In total, 5 units of onabotulinumtoxinA were injected intradermally into each wound edge and a further 15 units were injected subdermally. At 17 days, the patient showed remarkably rapid healing with minimal visible hypertrophic scarring. After 2 months of follow up, there has been no recurrence of the cyst.
There is no precedent in the literature for using adjuvant BoNTA to aid wound healing after sebaceous cyst excision. However, a case report from 2005 highlighted the disappearance of a 2 cm sebaceous cyst on the forehead, secondary to intramuscular injection of the area with 75 units of BoNTA for the treatment of migraine.14 There was no recurrence of the cyst.