There is increasing support for the use of botulinum toxin in emerging off-label aesthetic uses of botulinum toxin in dermatology, a systematic review has found.

Although the evidence remains weak, a review of randomised trials, observational and cohort studies, as well as case reports has highlighted the potential for botulinum toxin to be used beyond its approved indications approved by the US Food and drug Administration, according to Dr Kevin Phan of St George Dermatology and Skin Cancer Centre, Sydney.

As lead author of the review, published in Dermatologic Therapy, he noted seven areas where botulinum toxin has been reported in the literature to have successful applications. These include

• Treatment of upper and midface

These indications including eyebrow lift, in which botulinum toxin may be used to paralyse the lateral brow depressors to mediate eyebrow elevation via unopposed action of the frontalis muscle. For bunny lines, (nasalis fanning rhytides) botulinum toxin may be injected higher on the nasal dorsum, to treat the contraction of transverse nasalis muscle and lower medial orbicularis muscles that produce horizontal lines over the nasal bridge. Botulinum toxin may also be useful to treat lowered nasal tip (tip ptosis) due to contraction of the depressor septi nasal muscle.

• Treatment of lower face

Emerging indication for botulinum toxin include gummy smile, in which the aim is to reduce contraction of the key targets, namely the levator labii superioris alaeque nasi bilaterally and depressor septi nasi muscles centrally. Botulinum toxin may also have applications in treating vertical perioral rhytids, drooping oral commissures, dimpled chin and platysmal bands .

• Wound healing and scar minimisation

Botulinum toxin may  improve the appearance of facial scars and have positive effects on scar formation at the cellular level. It has also been used for patients undergoing surgical reconstruction following Mohs micrographic surgery for skin cancer.

• Keloids and hypertrophic scars

Clinical trials have suggested that suggest that botulinum toxin type A may decrease keloid symptoms as effectively as intralesional steroids without the associated serious adverse events. However some studies and case reports have reported variable effects.

• Oily skin / pore size reduction

An apparent effect of botulinum toxin in reducing oily skin was noted initially as a side effect of forehead line treatment. It has since been increasingly used for this benefit but the mechanism of sebum reduction is not understood. There is promising preliminary evidence suggesting a potential role for the use of intradermal botulinum toxin injections for management of enlarged facial pores, but further research studies are needed.

• Rosacea

A possible benefit of intradermal botulinum toxin for facial erythema was noted more than a decade ago, and there have since been case reports and clinical trials showing some efficacy in selected patients to improve facial flushing associated with rosacea, although the effects last only some months before requiring further repeat injections

• Contouring of face, calf and shoulder

Interest in the use of botulinum toxin for facial contouring is increasing, and it may help where there is repeated jaw clenching and muscle becomes hypertrophied, producing a bulging lateral jawline. For shoulder contouring botulinum toxin may be of particular benefit in patients with trapezius muscle hypertrophy that results in a masculine silhouette. Botulinum toxin has also been used for non-cosmetic purposes in the shoulder region for cervical dystonia, where it causes relaxation in muscle tone, reduces motor unit potential size and force of contraction, which alleviated pain symptoms and improved posture.

Dr Phan and co-authors also note that there are several botulimun toxin formulations available and they are not interchangeable, with individualized units and doses for each product.

“With the increasing number of formations and available products as well as expanding indications, it is important that techniques have ongoing evaluation that seek to compare efficacy, dosing, and longevity of outcomes. Further ongoing studies are required to assess emerging indications,” they conclude.