Is your wide jaw caused by muscle or salivary glands? How to tell before jaw Botox

What makes the jaw look wide?

There are four main reasons the lower face looks wide or heavy. The chewing muscle (masseter) may be thick, the parotid salivary gland below the ear may be enlarged, the angle of the jawbone may be naturally prominent, or there may be fat or sagging along the jawline.

Botox can reduce only two of these: the masseter and the salivary gland. Botox does not change bone shape, and fat or sagging responds better to lifting or fat-reducing treatments. So before jaw Botox, we first check where the width of your face is coming from.

How can I tell muscle from salivary gland at home?

The easiest way is to place both hands on the corners of your jaw and clench your teeth firmly. If a hard mass bulges outward under your fingertips, the masseter is well developed.

If nothing hardens when you clench, but the area from just in front of the ear to below the earlobe is soft and puffy, the parotid gland may be enlarged. The parotid gland sits over the back upper part of the masseter, so when it grows, the side of the face spreads toward the ear and the line between jaw and neck becomes blurred.

Many faces have both. If your masseter has shrunk well after several rounds of masseter Botox but the area below the ear still looks wide, the salivary gland may be the remaining cause. In clinic we use the clench test and palpation, and when the boundary is unclear we sometimes check muscle thickness and gland position with ultrasound.

How does masseter Botox work?

Masseter Botox injects botulinum toxin into the masseter to temporarily block the nerve signals that make the muscle move. As the muscle is used less, it slowly loses volume and the angular corner of the jaw softens.

Change comes in stages. At around 1–2 weeks, you first notice less force when chewing hard food. The contour usually slims over 4–8 weeks. Muscle volume returns after about 3–6 months, but with regular repeat treatments the muscle often regrows more slowly.

The dose depends on muscle thickness and left-right difference. The 50U on our menu is a standard dose; for thick muscles or strong grinding or clenching habits, we consider 100U. If chewing on one side has made the two muscles different sizes, we split the dose unevenly between sides.

My cheeks are already hollow. Won't jaw Botox make them sink further?

People with a peanut-shaped face, where the side cheek hollows just below the cheekbone, often avoid jaw Botox altogether for fear of looking more sunken. Hollowing after masseter Botox has indeed been reported. The usual causes are injecting too high or using too much, so the toxin reaches the upper masseter right under the cheekbone [1]. In a cadaver study, a larger injection volume at the same spot spread upward past the line joining the mouth corner and the front of the ear [2].

So the more hollow the cheek, the more we keep injections to the lower part of the masseter, close to the jawline. In a study of 45 women who already had hollow cheeks, the upper limit of the injection zone was set lower than usual so the toxin went only into the lower masseter. Over four weeks no one's hollowing got worse, and in some the hollowing improved by one grade [3].

The masseter is a layered muscle. When only its lower part is weakened, the untreated upper part can take over more of the work and thicken, a change called compensatory hypertrophy. Anatomical studies and case reports describe it as the upper masseter filling out after long-term, repeated lower-masseter Botox [4][5]. In someone whose face is wide to begin with, this is a change to manage, but in a face that is hollow below the cheekbone, the extra volume of the upper part can help support the sunken area. If you have been putting off jaw Botox because of hollow cheeks, our view at SERENE is that Botox focused on the lower masseter may actually help smooth the side cheek line.

That said, the study that observed improvement was small and short [3], and no comparative trial has yet shown that compensatory hypertrophy fills hollow cheeks. If the hollow is deep, or fat loss and skin laxity are also involved, jaw Botox alone is not enough, and we also consider placing a small amount of filler just inside the edge of the hollow.

How is salivary gland Botox different from masseter Botox?

Salivary gland Botox is injected into the parotid gland, not the masseter, in divided doses. When the toxin blocks the nerve signals that tell the gland to secrete, the gland becomes less active and shrinks in size.

The injection sites are in front of the ear and below the earlobe, further back than masseter Botox, and the dose is spread across several points so it distributes evenly through the gland. If someone with an enlarged gland only repeats masseter Botox, the muscle shrinks but the swelling below the ear stays. So we do one or the other based on the cause, or both on the same day.

After salivary gland Botox, saliva may decrease temporarily and your mouth may feel dry. This usually settles or becomes unnoticeable within a few weeks, but tell us before treatment if you already have significant dry mouth or a condition that causes dryness.

Can I get Botox in both the parotid and submandibular glands at once?

Two salivary glands can make the lower face look wide. The parotid gland, in front of the ear and below the earlobe, makes the side of the face spread out, and the submandibular gland, on the inner side below the jawline, blurs the line under the jaw.

The two glands make saliva at different times. At rest, the submandibular glands produce about 60% of saliva and the parotid glands about 25%, while during chewing the parotid share rises to 50–70% [6]. If only one gland is treated, the other keeps producing saliva, but treating both at once reduces saliva both at rest and while eating.

This is exactly why both glands are injected together when treating patients who drool. In sialorrhea treatment, splitting the dose between the parotid and submandibular glands on the same day is the recommended approach [7], and a randomized controlled trial of this method showed a clear drop in saliva production [8]. That is the goal when the aim is less saliva, but for someone with normal saliva who is treated for facial contour, it means dry mouth can be correspondingly stronger.

In a study of drooling treatment in children with developmental disabilities, four-gland injections that added the parotid glands caused eating and swallowing problems about as often as submandibular-only injections, but moderately severe problems were more common (33.3% vs 10.1%) [9]. A case has also been reported in which cosmetic injections into both submandibular glands spread to nearby swallowing muscles and caused severe swallowing difficulty lasting several months [10].

For this reason, at SERENE we advise against treating both glands in one session. We suggest starting with the one that contributes more to facial width, checking the response, and then planning the next step. No study has yet directly compared dry mouth after treating both glands versus one in cosmetic patients, so this advice is a judgment based on salivary physiology and treatment studies.

Why do salivary glands enlarge, and when should you see a doctor before Botox?

Painless, even enlargement of both parotid glands is known to be linked to frequent drinking, repeated binge eating and vomiting, metabolic conditions such as diabetes, and some medications. Some people simply have larger glands without a clear cause. If the habit behind it continues, salivary gland Botox may also last a shorter time.

In the following cases, see an ENT specialist before any cosmetic treatment: only one side is enlarged, you can feel a hard lump, it grew quickly over a short time, it hurts when pressed, you have a fever, or pus-like fluid comes into the mouth, or your eyes and mouth are both very dry. Inflammation, stones, tumors, or autoimmune disease of the gland need to be checked first.

When is jaw Botox not a good fit, or when should you be careful?

If the width comes mainly from bone, Botox makes only a small difference. If the jawline looks heavy because of fat or sagging, shrinking the masseter will not sharpen the contour and may make sagging look more obvious. If hollow cheeks are a concern, we keep the injections low on the masseter, as explained above. For people in their 40s or older with reduced skin elasticity, we keep the dose conservative and plan it together with lifting when needed.

After masseter Botox, you may feel tired chewing tough food or get bruising at the injection site. Rarely, if the toxin spreads toward the smile muscle, the corners of the mouth may look uneven when smiling; this usually recovers within a few weeks. We do not treat people who are pregnant or breastfeeding, or who have a neuromuscular disease.

How often should I get it, and what should I avoid afterward?

At first, repeat it at around 3–6 months when the effect fades, then widen the interval once the muscle has shrunk enough. To lower the chance of developing antibodies to the toxin, we do not repeat it at intervals shorter than 3 months, and we use the lowest dose needed.

On the day of treatment, do not rub or massage the injection area hard, and avoid saunas and heavy drinking. For a few weeks afterward, cutting back on foods that take long chewing, such as dried squid or gum, reduces the stimulus that makes the muscle grow back.

Prices (as of the October 2026 menu)

Korean toxin pricing is based on Hutox. The areas and dose you need are decided after consultation.

Frequently asked questions

References

1. Peng HLP. Masseter Hypertrophy: Toxin Treatment Techniques, Causes of Complications, and Prevention. In: Serdev N, ed. Botulinum Toxin. IntechOpen; 2018.
2. Yu P, Zhai H, Li Z, et al. Pivotal role of injection volume on sunken cheek prevention in masseter muscle BoNT-A injection: A cadaver study. J Cosmet Dermatol. 2022;21(1):137-141.
3. Huang SL, Guo Y, Liu J, et al. A Novel Injection Technique to Prevent Exacerbation of Sunken Cheek After Botulinum Toxin Type A Treatment for Masseter Hypertrophy: A Prospective Clinical Study. J Cosmet Dermatol. 2025;24(4):e70120.
4. Lee KL, Cho HJ, Bae H, et al. Anatomical Considerations When Treating Compensatory Hypertrophy of the Upper Part of the Masseter after Long-Term Botulinum Neurotoxin Type A Injections. Toxins (Basel). 2020;12(3):202.
5. Yi KH, Wan J. Compensatory Masseteric Bulging: A Novel Observation and Its Implications for Botulinum Neurotoxin Injection Techniques. J Cosmet Dermatol. 2025;24(4):e70090.
6. Humphrey SP, Williamson RT. A review of saliva: normal composition, flow, and function. J Prosthet Dent. 2001;85(2):162-169.
7. Jost WH, Bäumer T, Laskawi R, et al. Therapy of Sialorrhea with Botulinum Neurotoxin. Neurol Ther. 2019;8(2):273-288.
8. Jost WH, Friedman A, Michel O, et al. SIAXI: Placebo-controlled, randomized, double-blind study of incobotulinumtoxinA for sialorrhea. Neurology. 2019;92(17):e1982-e1991.
9. van Eck RM, Orriëns LB, Delsing CPA, et al. Negative effects on oral motor function after submandibular and parotid botulinum neurotoxin A injections for drooling in children with developmental disabilities. Dev Med Child Neurol. 2025;67(5):656-664.
10. Yang S, Yi YG. Dysphagia After Cosmetic Submandibular Gland Botulinum Neurotoxin Type A Injection: A Case Report. Healthcare (Basel). 2026;14(2):235.