Korea masseter Botox is botulinum toxin type A injected into the chewing muscle at each angle of the jaw, so the muscle relaxes and slowly thins and a square lower face looks narrower. For students and young workers living around Hongdae, being in Seoul changes the plan: you can attend a review a few weeks later, watch the change build, and decide on a second dose in person instead of guessing from abroad. The injections take minutes after ice or numbing cream. Chewing can feel weaker for a while, and bruising or uneven sides are possible. This page sets out a first-year calendar, the questions worth asking at the first visit, and the side effects to watch for.
Guide
A first-year jaw calendar for Seoul residents
Jaw Botox in Korea works slowly. The muscle stops bulging within days, but the slimmer outline appears over several weeks as the muscle loses bulk, and it fades again over months if no further dose is given.
The calendar below is a common frame that doctors adjust to each face.
| Point in time | What usually happens | What to do |
|---|---|---|
| Injection day | Small marks, possible tenderness or a bruise | Avoid massaging the jaw and hard exercise |
| Weeks 1 to 2 | Clenching feels softer, tough food takes more effort | Note any difference between the left and right side |
| Weeks 4 to 8 | Lower face looks narrower in photos | Attend a review and compare with your baseline photos |
| Months 3 to 6 | Muscle begins to regain strength | Discuss with the doctor whether a second dose is needed |
| End of year one | Pattern of your own response is clear | Agree on a spacing that suits you, or stop |
Guide
What a 239-patient review found about technique
Placement matters as much as dose. In a retrospective study in Aesthetic Plastic Surgery in 2026, Qian and colleagues reviewed 239 patients, average age about 30, treated with a fan-shaped injection from a single entry point deep in the lower masseter. Facial width fell at all three measured levels, most at the line of the mouth corners. Two of the 239 had a temporary local bulge that settled on its own, and no lasting cheek hollowing, smile asymmetry or chewing weakness needing treatment was found during follow-up of about five months.
The authors stress that the design was retrospective and that controlled studies with longer follow-up are still needed. Ask how many points go into each side and how deep.
Guide
When the jaw is wide and the chin is short
Toxin narrows the jaw but does not add length to the face. In 2016 in Aesthetic Surgery Journal, Chang and Kang described 13 patients with wide, short faces who had fat grafting to the chin together with one to three rounds of masseter toxin. The ratio of jaw width to facial height moved from 0.599 to 0.569 and no complications appeared during follow-up averaging 20 months.
The series was small and combined two procedures. It is a reason to ask the doctor whether your concern is width, length or both before committing to a year of injections.
Guide
Questions worth asking before the first injection
The first appointment sets the pattern you will repeat, so write the answers down.
- Is my wide jaw mainly muscle, or does bone or fat play a bigger part?
- Which toxin brand is used, and how many units go into each side?
- Will both sides get the same dose if one muscle is larger?
- Is the quote for one side or both, and is it shown before VAT?
- What should I tell my dentist or orthodontist?
Guide
Eating, exams and side effects to watch for
Weaker chewing is the effect people notice first. Chewy rice cakes, dried squid or hard bread can feel tiring for a few weeks. If you clench through exam season, the softer bite can feel strange at first; mention clenching to the doctor.
Other effects include bruising, tenderness, a temporary bulge when clenching, uneven sides, and, if toxin spreads to nearby muscles, a change in the smile. Pregnancy, breastfeeding, neuromuscular disease and infection at the site are reasons to wait. Results vary from person to person.
Evidence
Research behind this page
- Fanning Deep Injection of Botulinum Toxin Type-A for Masseter Hypertrophy: A Retrospective Study of 239 PatientsAesthetic Plastic Surgery · 2026 · doi:10.1007/s00266-026-06223-1
In 239 patients treated with a single-entry, fan-shaped deep masseter injection, facial width decreased at all measured levels and two had a temporary local bulge, with no lasting smile asymmetry or chewing weakness seen in follow-up.
- Achieving Ideal Lower Face Aesthetic Contours: Combination of Tridimensional Fat Grafting to the Chin with Masseter Botulinum Toxin InjectionAesthetic Surgery Journal · 2016 · doi:10.1093/asj/sjw082
In 13 patients with wide, short faces, chin fat grafting plus one to three masseter toxin injections improved the jaw-width to facial-height ratio, with no complications over a mean 20-month follow-up.
FAQ
Questions about Botox in Hongdae
Can I chew normally during finals week after jaw injections?
You can eat normally, but tough or chewy food may feel tiring for several weeks after jaw injections. The bite usually weakens within the first one to two weeks and recovers gradually. If finals fall soon after, choose softer meals and avoid gum. Some people who clench under stress find the softer bite helpful, while others find it distracting and mention it at the review.
Could masseter Botox in Seoul change how my smile looks?
It can, though it is uncommon when the injections stay deep and low in the muscle. Toxin that spreads to the muscles near the mouth can make a smile look uneven for some weeks. In the 2026 review by Qian and colleagues, no lasting smile asymmetry was reported with a deep fan-shaped technique. Ask how deep the points will be.
What if one side bulges when I clench a few weeks later?
A small bulge on clenching usually means part of the muscle was not reached, and it is often adjusted at a review. In the Qian study it happened in two of 239 patients and settled without treatment. Take a photo while clenching, compare both sides, and show it at the follow-up rather than massaging the area yourself, since pressure on fresh points is discouraged.
Will a slimmer jaw make my face look longer?
It narrows the lower face but does not add length, so a face may look longer only because it is slimmer. In the small 2016 series by Chang and Kang, people with short faces had chin fat grafting alongside toxin to change proportions. If length is your concern, ask whether a chin treatment should be part of the discussion before a second dose.
What does the injection actually feel like?
Most people describe a short sting and some pressure, followed by a dull ache for a day. Ice or numbing cream is commonly used first, and the injections themselves take only a few minutes. In the Qian review the average pain score was low, about one on a ten-point scale, but sensitivity differs from person to person and with the number of points.
What if I leave Seoul before my next dose is due?
Ask for a written record of the brand, units per side and injection pattern before you leave, so a doctor elsewhere can continue the plan. The jaw slowly returns toward its earlier width over months if no further dose is given. Baseline and review photos taken in the same light will also help the next doctor judge how your muscle has responded.