Medically reviewed by Jacquelyn McDowell, FNP-C, Medical Director, and Courtney Strocky, NP. Last reviewed November 11, 2026.
Masseter Botox is an injection of a neuromodulator into the masseters, the large chewing muscles at the back of the jaw. Relaxing those muscles does two things. Over a couple of months the muscle gets smaller, so a square or wide lower face looks softer and slimmer. And because the muscle cannot contract as hard, many people who clench or grind their teeth feel less tension and jaw pain. Results build slowly, so this is a treatment for patient people, and it needs repeating to keep the effect.
What is the masseter muscle?
The masseter runs from the cheekbone down to the angle of the jaw, on both sides of the face. It is the main muscle you use to bite down. Put your fingers just in front of your earlobes, below the cheekbone, and clench your teeth. The muscle you feel bulge is the masseter.
Some people have naturally large masseters. Others build them up over years of clenching, grinding at night, or chewing gum. A large masseter widens the lower face at the jaw angle, which can make the face look square or heavy at the bottom even in someone who is otherwise slim.
How does masseter Botox work?
Botulinum toxin temporarily blocks the nerve signal that tells a muscle to contract. In the masseter, that means the muscle works less hard. A muscle that works less gets smaller over time, the same way an unused muscle anywhere else in the body shrinks. As the masseter shrinks, the width at the jaw angle reduces and the lower face takes on a softer, more tapered shape.
The same relaxation is what helps with clenching. The muscle can still chew normally, but it cannot clamp down with the same force.
On Glam's Botox and injectables page, Masseter Reduction and Jawline Slimming is described as injecting neurotoxin into the large masseter muscles to create a slimmer jawline, with the page noting it also helps with TMJ disorders, headaches from jaw clenching, and jaw tension.
Using botulinum toxin in the masseter is an off-label use, which is common practice in aesthetic medicine. Your injector should tell you that before treatment.
What does the research show?
For jaw slimming, the evidence is consistent and mostly from smaller studies. A 2023 review in Bioinformation looked at 20 publications on reducing lower-face width with botulinum toxin in the masseter. The authors found the treatment reduced width by reducing muscle volume, reported no permanent adverse events, and advised repeat treatment at regular intervals to maintain results. They also called for larger randomized trials to settle the best dose and frequency.
That call for better trials is fair. A Cochrane review published in 2013 searched for randomized or controlled trials of botulinum toxin for benign masseter enlargement and found none that met its criteria. Since then more studies have been published, but dosing still varies widely from study to study.
For clenching and grinding (bruxism), a 2019 systematic review of four randomized trials found botulinum toxin injections reduced bruxism episodes, pain, and maximum bite force compared with placebo or traditional approaches. A 2023 meta-analysis in Aesthetic Plastic Surgery found botulinum toxin reduced biting strength and pain, with effects showing in under four weeks, peaking between five and eight weeks, and lasting up to 24 weeks. The same analysis found that a night guard (oral splint) had a more lasting effect after about nine to twelve weeks. Botox and a night guard can work together, and the meta-analysis authors suggest Botox for people who struggle to wear a splint or want earlier relief.
Taken together, the studies support masseter Botox for softening a jaw made wide by a large masseter, and for easing clenching symptoms, though most of the research comes from small studies.
Who is masseter Botox best for?
It tends to suit you if:
- your lower face looks wide or square at the jaw angle, and the muscle bulges when you clench
- you clench during the day or grind at night, wake with a sore or tired jaw, or get tension headaches at the temples
- you have been told by a dentist that your teeth show wear from grinding
- you want a softer lower face without filler or surgery
It is less likely to help if the width of your jaw comes from bone structure, or if the fullness is fat under the jawline. Fullness under the chin is a different concern with different options.
If your main concern is jaw pain, clicking, or locking, see your dentist or doctor as well. Jaw joint disorders have several possible causes, and Botox treats only the muscle part of the picture.
How long does masseter Botox take to work, and how long does it last?
- First 1 to 2 weeks: The muscle starts to relax. Clenching may ease and chewing hard foods can feel tiring.
- Weeks 4 to 8: Clenching relief is usually at its best. The 2023 bruxism meta-analysis found effects peaked between five and eight weeks.
- Roughly 2 to 3 months: Visible slimming of the jaw angle as the muscle shrinks.
- Several months later: The effect fades gradually as nerve signaling returns.
- With repeat treatment: The muscle stays smaller between sessions, which is why the research recommends repeating treatment at regular intervals.
Because the shape change depends on the muscle shrinking, you will not see slimming in a mirror the week after treatment. Glam's page notes that Masseter Reduction is done in a series, which matches the research recommendation for repeat treatment at regular intervals. How many sessions you need, how far apart they go, and how often you maintain afterward depend on your muscle and your goals, and your injector sets that plan at your consultation.
What are the side effects of masseter Botox?
Most side effects are mild and temporary:
- tenderness, small bumps or bruising at the injection sites
- tired jaw when chewing tough foods like steak, bagels or gum, usually in the first few weeks
Less common effects come from the product reaching a nearby muscle or from too strong a dose:
- an uneven smile, if the toxin affects a smile muscle near the masseter
- a bulge in part of the muscle that was not fully treated, which can be corrected at follow-up
- a hollow look under the cheekbone in people who already have a lean face
This is why placement and dosing matter so much. The injector needs to map the muscle with you clenching, stay in the safe zone of the masseter, and dose for your face. Masseters vary a lot in size and strength from person to person, so the number of units and the neuromodulator used are chosen for you at your appointment.
What happens at a masseter Botox appointment?
Courtney will look at your face at rest and while you clench, feel the muscle on both sides, and ask about clenching, grinding, headaches and dental history. If one side is larger than the other, each side is dosed to match.
The injections themselves are quick, with a few points on each side. Glam lists the appointment at 30 minutes.
Aftercare follows Glam's general Botox guidance:
- avoid lying down for at least four hours
- skip exercise for 24 hours
- do not touch, rub or massage the area
- avoid alcohol for a day, since it raises the chance of bruising
- if you take a blood thinner, tell your injector beforehand, and do not stop a prescribed medication without asking the doctor who prescribed it
Chewing normally is fine. If you chew gum often, cutting back helps the muscle stay relaxed.
Masseter Botox at Original Glam
Masseter Reduction and Jawline Slimming is listed at $400 for a 30-minute appointment on Glam's Botox and injectables page. It is performed by Courtney Strocky, NP, one of our injectors. Courtney also treats forehead lines, frown lines and crow's feet, and many patients combine masseter treatment with their regular Botox appointment. Your consultation will cover what your full plan looks like and what it costs.
If you are new to Botox, Glam offers a personalized consultation at $50 for 45 minutes.
Original Glam is at 4635 West Colfax Ave, Denver, CO 80204.
Frequently asked questions
Does masseter Botox change your face shape?
It can. As the masseter shrinks over roughly two to three months, the jaw angle narrows and the lower face looks softer. How much depends on how large the muscle was to begin with.
Will Botox in my jaw affect chewing?
You can chew normally. Many people notice tough or chewy food tires the jaw more for the first few weeks, which eases as you adjust.
Does masseter Botox help with teeth grinding?
Research shows it can reduce bruxism episodes, pain and bite force. A night guard still protects your teeth and may give a more lasting effect, so many people use both. Check with your dentist about a night guard.
Can masseter Botox help TMJ pain?
It can relieve the muscle tension and clenching that contribute to some jaw pain. Jaw joint problems have several causes, so see your dentist or doctor for a diagnosis if you have clicking, locking, or ongoing pain.
How long does masseter Botox last?
The effect fades over several months. The 2023 bruxism meta-analysis reported effects lasting up to 24 weeks. Glam's Botox page notes that results may last longer over time with regular treatment.
Can masseter Botox make my face look sunken?
In someone who already has a lean face or a small masseter, it can create a hollow under the cheekbone. A good assessment should catch this before treatment.
Is masseter Botox the same product as forehead Botox?
The product is a neuromodulator, the same family used for forehead lines and crow's feet. The masseter is a much larger, stronger muscle, so the dose and placement are different, and the goal is to shrink the muscle over time as well as relax it. Glam's Botox page lists Botox, Xeomin, Dysport and Daxxify among its neuromodulators.
When will I see a slimmer jaw?
Clenching relief often comes first, within a few weeks. The shape change follows as the muscle gets smaller, usually over two to three months. Taking photos from the front before treatment and again at three months makes the change easier to see, since it happens too gradually to notice day to day.
Can I stop treatment once my jaw looks slimmer?
You can stop at any time. The muscle gradually regains its size and strength as the effect wears off, so the jaw returns toward its original shape over the following months. Nothing about stopping is harmful.
How much does masseter Botox cost at Original Glam?
Masseter Reduction and Jawline Slimming is listed at $400 for a 30-minute appointment.
Talk it through with Courtney
If you clench, grind, or have wondered whether your jaw muscle is behind a wide lower face, a consultation will give you a clear answer and a realistic timeline. Book a consultation at Original Glam.