Skin Guide · Sep 2026
Skin Guide
A jaw that slims slowly
Masseter Botox rests an overworked chewing muscle until it shrinks. It works only when the width is muscle.
Weeks
four to
eight
Maylin Apgujeong
Model portrait
Not a patient
Skin Guide · Botox
Masseter Botox for Jaw Slimming: A Seoul Clinic Guide
Masseter Botox relaxes the large chewing muscle at the back of the jaw. When that muscle is what makes the lower face look square, resting it lets the jawline slim gradually over about two months. It is one of the most requested uses of Botox in Seoul, and it works only when the width comes from muscle, not from bone or fat. A doctor checks that first by feeling the muscle while you clench.
Maylin Apgujeong · Skin Guide
What the masseter does, and why it widens the jaw
The masseter runs from the cheekbone down to the angle of the jaw. It does the heavy work of chewing, and it grows the way any muscle grows when it is used a lot. Clenching, grinding at night, and chewing gum or tough food every day can all build it up. When it is large, the lower face looks broad and square even in people with a slim build.
Botulinum toxin blocks the signal that tells the muscle to contract. A muscle that works less, shrinks. That is the whole idea behind jaw slimming with Botox: it does not dissolve anything, it lets an overworked muscle rest until it becomes smaller.
Is the width muscle, bone or fat?
This is the question that decides whether masseter Botox is the right treatment. Three different things can make a jaw look wide:
- Muscle: you can feel a firm bulge at the jaw angle that hardens when you bite down. This is what Botox treats.
- Bone: a wide or flared jaw bone does not change with Botox.
- Fat or loose skin: softness along the lower face and jowls needs a different approach, such as lifting treatments.
Many faces are a mix. A doctor examines you in person, asks you to clench and relax, and tells you honestly how much of the width is likely to change.
What the treatment is like
- Time: the injections themselves take a few minutes. Most of the appointment is the consultation and marking.
- Feel: a few small injections on each side, with a brief sting. Numbing cream can be used.
- Dose: set per side after examination. Muscles are rarely identical, so both sides are not always treated the same.
- Afterwards: you can go back to your day. Avoid pressing or massaging the area and skip heavy exercise and saunas for the rest of the day.
Timeline: when the jaw starts to slim
- First 1 to 2 weeks: the muscle weakens. You may notice chewing feels a little tired with tough food.
- Weeks 4 to 8: the muscle shrinks and the lower face starts to look narrower in photos.
- Around 2 to 3 months: the slimming is usually at its most visible.
- After that: the effect fades slowly as the muscle recovers. The jaw muscle tends to hold longer than lines on the upper face, and with repeated treatment the muscle often stays smaller.
Because the change is gradual, it looks natural. People around you tend to notice that your face looks softer, not that you had something done.
How the jaw slims over time
Masseter Botox, illustrated
Three illustrations cover what masseter Botox is, how it changes the jawline, and what to expect from the treatment.
Illustration only. These are conceptual educational illustrations, not actual patient results.
Side effects to know about
- Small bruises or tenderness at the injection points, usually gone in a few days.
- Chewing fatigue with hard food for the first weeks.
- Rarely, a slightly uneven smile if the toxin affects a nearby muscle. This is temporary and settles as the effect wears off.
- If the muscle is treated too strongly, some people notice a hollow look below the cheekbone. A conservative dose avoids this.
Botox is not recommended during pregnancy or breastfeeding, or for people with certain neuromuscular conditions. Tell the doctor about your health history and any medication before treatment.
Masseter Botox for clenching and grinding
Some people come for jaw slimming and find their clenching eases too. Others come for the clenching first. Relaxing the masseter can reduce the force of grinding and the ache that comes with it. If jaw pain or grinding is your main concern, mention it at consultation so the plan covers it, and keep seeing your dentist about your teeth.
Other areas people treat at the same visit
Many visitors combine jaw slimming with softening expression lines, such as crow’s feet around the eyes or bunny lines on the nose. Men often want a plan built around a stronger jaw and a lower brow; men’s Botox explains how that differs. Each area is planned on its own, and the doctor explains what makes sense for your face rather than treating everything at once.
Doing it safely in Seoul
At Maylin Apgujeong, a doctor examines your jaw before anything is decided, explains in writing what is likely to change and what is not, and sets a dose that keeps the result natural. Consultation is in English. If you are visiting Korea for a short stay, the timing is easy: the treatment is quick, and the slimming shows up after you are home.
How many units for the masseter?
The dose depends on how bulky the muscle is. A commonly used range is around 20 to 50 units per side in Botox units, with smaller muscles at the lower end. The doctor feels the muscle while you clench and sets the dose from that.
Unit numbers here are in Botox (onabotulinumtoxinA) units; other products are dosed differently, so numbers are not interchangeable.
Why visitors ask for it in Korea
Jaw slimming is one of the most common treatments in Korean clinics, and visitors often combine it with a trip because the visit is short and needs no downtime. The slimming shows over the following weeks, usually after you are home, so we take photos before treatment.
FAQ
How long does masseter Botox last?
Usually several months. The jaw muscle often holds longer than lines on the forehead or around the eyes, and repeat treatments can extend it.
Will it change how I chew?
You may feel mild chewing fatigue with hard food in the first weeks. Everyday eating is not affected.
Can it make my face look sunken?
Not when the dose fits the muscle. A conservative plan keeps the jawline soft without hollowing the cheek.
When will I see the result?
Expect gradual slimming from around the fourth week, with the clearest change at two to three months.
What are the downsides of masseter Botox?
Chewing fatigue for a week or two, tenderness or a bruise, and less often an uneven smile if product spreads. It needs repeating to keep the result.
How many units of masseter Botox do I need?
Commonly around 20 to 50 units per side in Botox units, depending on muscle size.
What is the riskiest place for Botox?
Areas near the eyes and brow, and high doses in the neck, carry the most notable risks. In the jaw, placing the product within the muscle protects the smile.
Plan a visit: send a front and side photo of your face on WhatsApp, LINE, or KakaoTalk. We will tell you whether masseter Botox is likely to help and what a visit would involve, in English, before you land.
This guide comes from Maylin Clinic Apgujeong, the Apgujeong branch of the Maylin Doctor Network in Gangnam, Seoul. You can meet our doctors before you book.
General information, not medical advice for your individual case. What is appropriate depends on your history and on an examination. See also our Medical Disclaimer and Medical Review Process.
Published · Updated
Medically reviewed by Hyoung Moon Kim, MD, PhD on .
From our channels
YouTube · from our channel
What to watch out for when botox is combined with energy devices
YouTube short on combining botox with energy-based devices
Watch on YouTube →
Instagram · from our channel
Dr. Kim on carbon shockwave lifting, KALDAT Busan 2026
Instagram reel of Dr. Kim lecturing at the KALDAT Busan symposium
Watch on Instagram →Not sure this is the right treatment?
That is what the consultation is for. We will look at your skin and tell you what we would recommend and what we would leave alone, including if the answer is nothing for now.
Book a consultation