Masseter Botox (Jaw Slimming)

Botulinum toxin blocks acetylcholine release at the neuromuscular junction, preventing the masseter muscle from fully contracting during chewing. The muscle undergoes disuse atrophy over 8–12 weeks, reducing its volume and therefore the visible width of the jaw. Typical dosing is 25–50 units per side. The effect lasts 4–6 months before the muscle re-bulks; over repeated treatments the atrophy can become semi-permanent.

Numbing cream, 2–4 injections per side into the masseter body. Mild soreness and a "fullness" sensation for 1–2 days. Chewing tough food feels slightly weaker for 2–3 weeks (this is the treatment working, not a side effect). Visible jaw-slimming starts at 3–4 weeks, peaks at 8–12 weeks. Combined with bruxism-relief benefits (stopping teeth grinding) that many patients find more valuable than the cosmetic change.

Masseter Botox is distinct from the facial anti-wrinkle Botox and the microdose "baby Botox" protocols — instead of targeting expression muscles, it injects higher doses of botulinum toxin type A directly into the masseter muscles (the chewing muscles on the jawline). The treatment was developed in Korea in the late 1990s as a non-surgical alternative to jaw-slimming surgery, and has since become one of the most-requested K-cosmetic procedures globally. Over 3 months the masseter atrophies from disuse, producing a visibly softer, less square jawline — plus significant relief from bruxism (teeth grinding) and TMJ tension.