Quick answer:
Jawline or masseter botox relaxes the chewing muscles at the back of the jaw so they gradually shrink, which can make a square lower face look slimmer. In Busan it is one of the most requested injectable treatments. Visible slimming usually takes four to eight weeks, and the effect typically lasts around four to six months.
Why Some Faces Look Wide at the Jaw
The masseter is a thick muscle running from the cheekbone to the angle of the jaw. People who clench, grind their teeth at night or chew gum frequently can develop a larger masseter, which gives the lower face a square or broad outline. Genetics and bone shape also matter. Before suggesting treatment, a doctor should check whether width comes mainly from muscle, from fat, from bone, or from a combination. You can often feel the muscle bulge yourself by clenching your teeth and placing your fingers just in front of the jaw angle.
How Masseter Botox Works
Botulinum toxin blocks nerve signals to the injected muscle. With less activity, the masseter slowly shrinks over several weeks, a process called disuse atrophy. This is why slimming is gradual rather than immediate. The treatment does not remove bone or fat, so a wide jaw caused by bone structure or a full lower face caused by fat will respond less, and a fat-targeting device or surgical consultation may be more relevant in those cases.
Korean and imported toxins approved by the Ministry of Food and Drug Safety (MFDS) are used for this purpose. Masseter reduction is widely practiced but is considered off-label for some products, so it is reasonable to ask the doctor about the product, dose and their experience with this area.
Results Timeline
- First one to two weeks:
chewing may feel slightly weaker, especially with tough foods. The face still looks the same.
- Four to eight weeks:
slimming becomes noticeable as the muscle reduces.
- Around two to three months:
the slimming effect is often at its most visible.
- Four to six months:
muscle strength gradually returns and the jaw may widen again.
Some people choose repeat treatments to maintain the result. With regular sessions, some find they need treatment less often, but responses vary and no outcome is guaranteed.
Other Benefits People Report
Because the muscle is relaxed, some people with clenching or night grinding (bruxism) report less jaw tension or morning tightness. Botulinum toxin for bruxism is an area of ongoing research and is not a replacement for dental assessment. If you grind your teeth, a dentist may also recommend a night guard.
Who Is a Good Candidate
- Adults with a square lower face caused mainly by masseter bulk
- People who clench or grind, after discussion with a doctor or dentist
- Those who want gradual change without surgery
Who should avoid or be cautious
- People who are pregnant or breastfeeding
- Those with neuromuscular disorders or an allergy to product components
- People with thin, lax skin along the jaw, especially in their late forties onward, as muscle reduction can sometimes make sagging more visible
- Anyone with temporomandibular joint problems, until assessed
- People whose jaw width is mainly due to bone or fat
Possible Side Effects
- Mild bruising or tenderness at injection points
- Temporary chewing fatigue, particularly with hard or chewy foods
- Smile changes:
if toxin spreads to nearby smile muscles, the smile can look uneven for several weeks
- Paradoxical bulging:
an uneven bulge when clenching if part of the muscle is untreated, which may need a touch-up
- Cheek hollowing or sagging:
more likely with high doses, repeated treatment or thin tissue
Accurate placement, an appropriate dose and anatomical assessment reduce these risks. Report any lasting asymmetry to the clinic, ideally with photos.
The Procedure
The doctor asks you to clench, palpates the muscle and marks safe injection points, staying away from the area closer to the mouth. A few injections per side are typical. The appointment is short, and most people return to their plans right away. Avoid massaging the jaw for the rest of the day and follow any advice about exercise or saunas.
Understanding the Price
Cost mainly depends on the toxin brand, the total units used for both sides, and whether a review visit is included. Some clinics advertise jaw botox at low event prices; check the brand, units and who performs the injection before comparing. A written quote stating these details plus VAT makes comparison straightforward.
Planning Around a Visit to Busan
Because slimming appears weeks later, you will not see the result during a short trip. A two-week review is helpful for checking symmetry, so if you are leaving earlier, ask whether the clinic will review photos online. Many visitors combine jaw botox with treatments for other areas in a single Seomyeon visit, but tell the doctor everything you plan to have done, including any lifting or fat-reduction devices.
Frequently Asked Questions
Will jaw botox make it hard to eat?
You may notice chewing fatigue for a few weeks, especially with tough foods such as dried squid or chewy rice cakes. Normal eating is usually unaffected.
Can jaw botox reduce a double chin?
No. It targets the masseter muscle at the side of the jaw. Fat under the chin requires a different approach.
Does masseter botox become permanent?
No. The muscle gradually regains strength, though some people need treatment less often after several sessions.
Why does one side look different?
Most faces are asymmetric, and muscles may respond differently. A review around two to four weeks allows small adjustments.
Key Takeaways
- Masseter botox slims the lower face by shrinking an enlarged chewing muscle.
- Results appear in four to eight weeks and usually last four to six months.
- It does not treat width caused by bone or fat.
- Risks include chewing fatigue, smile asymmetry and, in some cases, more visible sagging.
Medical disclaimer: This article is for general education only and does not replace a consultation with a licensed physician. Treatment suitability, results and risks vary by individual. In an emergency in Korea, call 119.
Last reviewed: October 2026.
