While botulinum toxin is most associated with forehead lines, the evidence base for its use elsewhere in the face and neck has grown substantially, with distinct considerations for male and female patients.
1. Masseter Muscle (Jaw Contouring)
For patients seeking a slimmer lower face or relief from masseter hypertrophy, toxin injection into the masseter is well established. Studies have reported favourable long-term efficacy, with a 12% reduction in masseteric muscle volume after three consecutive injections, sustained one year after treatment completion . Botulinum toxin type A injections are now the standard non-surgical treatment for masticatory muscle hypertrophy, improving both facial aesthetics and associated symptoms such as jaw fatigue and discomfort , though consensus on optimal average dosage hasn’t yet been firmly established .
2. Lower Face and Neck (Platysma, Marionette Lines, Perioral Area)
A systematic review of aboBotulinumtoxinA use specifically in the middle and lower face and neck found consistently positive results. Across ten included articles covering marionette lines, masseter volume, nasal wrinkles, perioral wrinkles, and the platysma muscle, all studies reporting on efficacy demonstrated improvement compared with baseline, with no serious adverse events reported . The upper platysma, though primarily a neck muscle, is closely linked to lower face contouring outcomes , making it a key target for jawline definition procedures.
3. Facial and Neck Scars
A more recent application is scar management. A 2024 systematic review and meta-analysis found that botulinum toxin A improved scars across the face, head, and neck compared with controls, with particularly strong outcomes in the upper lip and forehead regions on subgroup analysis.
Sex-Based Differences Matter
Importantly, treatment isn’t one-size-fits-all. Men typically require higher doses than women to achieve the same clinical effect , a finding attributed to greater skeletal and facial muscle mass in men, along with more pronounced facial movement and deeper rhytids . Real-world data reflects this: in one cross-sectional analysis, men received significantly higher doses in the procerus and nasal muscles than women , while dosing and product choice were also shaped by differing aesthetic goals between sexes — men favouring structural enhancement, women favouring softer aesthetic regions .
Safety Profile
Across these non-forehead applications, the safety profile remains reassuring when technique is correct. Complications such as unnatural smile or sunken appearance, occasionally seen with larger-volume injections like masseter treatment, typically resolve within one to two months and can be minimised by precise, deep-level placement of the toxin .
Conclusion
The evidence supports botulinum toxin’s expanding role well beyond the forehead, with masseter reduction, lower face/neck contouring, and scar improvement all backed by systematic review data. Effective treatment, however, depends on tailoring dose and technique to each patient’s anatomy and goals — including meaningful differences between men and women.
References:
1. Kassir et al., J Cosmet Dermatol, 2024 (lower face/neck review)
2. Galadari et al., Toxins, 2021, DOI: 10.3390/toxins13020169
3. Rammal et al., Facial Plast Surg Aesthet Med, 2024
4. Key Clinical Postulates II, PMC7693297
5. Cross-sectional sex/age analysis, ScienceDirect, 2025
