Whether you need 50 or 100 units of jaw Botox depends on how thick your chewing muscle is, and the first thing to settle is whether the number on a quote counts one side or both sides together. In the masseter trials I'll walk you through, a mid-range total dose did most of the work, while the top dose added complaints rather than a clear extra gain.

Xeomin versus a Korean brand changes the label more than the plan. Product choice starts to matter when you've had several rounds and the effect seems to fade sooner than it used to.

If you're reading this before a trip to Seoul, you've probably seen a jaw quote written as 50U next to another written as 100U, maybe with Xeomin offered as an upgrade. You want to know which one gets you a slimmer jawline without a stiff smile, and whether one visit before your flight home is enough. In this article, we'll cover what those unit numbers mean, how to tell muscle from fat, when the product matters, the side effects that come from dose and placement, and how to fit it into a short stay.

Jaw Botox 50U or 100U: Is That Per Side or Total?

Ask before you compare: a single unit number can describe one side or the whole jaw, and the dose trials I rely on counted both sides together.

A multicenter phase II trial of Botulax in Asian patients assigned people to a placebo group or to 24 U, 48 U, 72 U, or 96 U, on both sides of the jaw. So a 50U quote for both sides sits near that trial's second arm, and a 100U quote sits near its top arm.

The authors concluded: "BTA administration of at least 48 U for BMH is more cost-effective than high-dose units and has a low risk of side effects." BMH stands for benign masseteric hypertrophy, the medical name for a bulky chewing muscle (masseter).

A dose-finding trial of prabotulinumtoxinA from a Seoul university department pointed the same way at the low end. Its authors wrote: "Despite being slightly effective, a dose of 24 units might be insufficient for resolving square face problems."

At the top end, that trial's highest group received 96 units, and "Patients in Group E reported discomfort during jaw movement."

Some protocols write the dose per muscle instead, which is exactly why the question matters. One tailored protocol used individualized botulinum toxin type A injection dosages (20 to 40 units) and sites (one to three per muscle).

There's no universal number yet. A meta-analysis of randomized, placebo-controlled trials concluded that current evidence is insufficient to define a formulation-adjusted dose-response relationship or an optimal treatment protocol.

My read: if this is your first jaw session and the muscle is clearly bulky, a mid-range total split evenly between both sides is the reasonable starting point. A 100U total is a number I'd want a reason for, such as a very thick muscle, rather than a default that sounds stronger.

Is My Square Jaw Muscle or Fat? Try the Clench Test

Clench your back teeth and rest your fingertips on the corner of your jaw, just in front of and below your earlobe: muscle hardens and pushes outward, while fat and skin stay soft and don't change shape.

That matters because Botox only works on muscle. It blocks the signal from nerve to muscle, so the masseter contracts less, and a muscle that's used less slowly loses volume. That's why the side of the face looks slimmer over weeks rather than the day after.

People who land here sometimes ask whether walking builds muscle. It's the right instinct, just pointed the other way: a muscle tends to match the work it's given, and a jaw that clenches hard every day can stay bulky. Botox doesn't burn the muscle off. It asks the muscle to do less.

Researchers who built a tailored dosing protocol classified each masseter by bulging type on clenching and muscle thickness.

An ultrasound study looked at the shape of the jaw angle plus the thickness of the masseter, and the thickness of subcutaneous fat. Subcutaneous fat simply means the fat just under the skin.

I think about a wide lower face in three parts, and each points to a different tool:

• Muscle: hard and bulging when you clench. This is where jaw Botox fits.

• Fat: soft, and it doesn't move when you clench. Botox alone isn't the tool for fat, so this is a different conversation at the exam.

• Bone: the jawbone itself is wide. No injection narrows bone.

Most faces are a mix. My call for your situation: if your jaw corner clearly hardens and bulges when you clench, Botox is a sensible first step. If it barely changes, I'd check fat and bone before you spend anything on units.

Xeomin or a Korean Brand for Masseter Botox?

In Seoul you'll usually see Korean-made toxins offered next to imported ones such as Xeomin. For a first jaw treatment, the product name matters less than the units per side and where they go. It starts to matter after many rounds, if the effect seems to be wearing off faster.

Xeomin (incobotulinumtoxinA) has its own masseter data. In a two-year study of Asian Indian patients, people were injected with 30 U Xeomin on each side of face. That's a per-side number, one more reason to ask how a quote counts.

Units also aren't a shared currency between brands, which is why the meta-analysis above couldn't set a brand-adjusted dose. A Xeomin quote and a Korean-brand quote with the same number aren't automatically the same treatment.

Where Xeomin differs is that it's made without complexing proteins, extra bacterial proteins that come along with the toxin in some products.

A review written by authors linked to Xeomin's maker reports that the rate of antibody-mediated secondary non-response is lowest in complexing protein-free (CF) IncobotulinumtoxinA (INCO). Secondary non-response means a toxin that used to work stops working as well.

Coretox is also listed in that review as complexing protein-free, but the authors added: "Presently, no data are available on the immunogenicity of CORE in human beings." Immunogenicity is the chance your body makes antibodies against it.

A review of non-response in aesthetic treatment states: "Switching to a protein-free BoNT-A formulation such as incobotulinumtoxinA upon development of SNR has been advocated." SNR is the same secondary non-response.

So my call is simple. If this is your first or second jaw session, choose on units per side and placement, and either kind of product is a reasonable start. If you've had several high-dose rounds and each one seems to fade sooner, that's when I'd bring up a complexing protein-free option such as Xeomin.

Masseter Botox Side Effects: Smile, Chewing, and Sunken Cheeks

Most jaw Botox side effects come down to how much toxin goes in and where it spreads, and the common one is simply that chewing feels weaker for a while.

In one Taiwanese clinic's record of 2036 treatment sessions, temporary mastication force decrease was reported after 611 (30%), bruising after 51 (2.5%). Mastication force just means chewing strength.

The ones people worry about were rarer in that record: smile limitation after 3 (0.15%), paradoxical bulging after 10 (0.49%), sunken cheeks (subzygomatic volume loss) after 9 (0.44%). Paradoxical bulging is a lump that shows up when you clench after treatment, instead of the flatter line you expected.

A stiff smile usually traces back to the front edge of the muscle, close to the small smile muscle beside the mouth (risorius). In a small Brazilian study of abobotulinumtoxinA, a different product with its own unit scale, the authors wrote that smile limitation may result from risorius muscle blockage caused by toxin dissemination.

Dose shows up here too. In the onabotulinumtoxinA phase 2 trial, "Localized impact on smile was reported with 96 U OnabotA (n = 4)."

The variable most people never hear about is fluid volume. The same units can be mixed into more or less saline, and more fluid travels farther inside the muscle.

A cadaver study using dye in place of toxin concluded: "The spread of indocyanine green within the masseter occurs in direct proportion to its volume."

In that study, "A bolus of 1 ml easily exceeded the mouth corner-tragus line and cause sunken cheek." The tragus is the small flap in front of your ear canal, so that line runs from the corner of your mouth to your ear.

The same 2036-session report advised keeping injections inside the muscle's safe zone, ideally in 3-4 different locations at least 1 cm from any border. Put together, that's why the points belong low in the muscle and away from its front edge, not up toward the cheek.

Bruising and soreness at the injection points are common. If they get worse instead of fading, contact your provider. If you have trouble swallowing, speaking, or breathing, or weakness spreading beyond your jaw, seek medical care right away.

Fitting Masseter Botox Into Your Seoul Travel Itinerary

Unless you're sedated on the day of treatment, there's no reason to push back your flight home because of jaw Botox. Whether a bruise might show in trip photos isn't something I'd promise either way, so mention your photo days when you book.

One visit is worth making, but you'll most likely fly home before the final shape shows. Jaw Botox doesn't change your face overnight. It moves you gradually toward a slimmer line, and in the prabotulinumtoxinA trial, ultrasound and 3D imaging revealed a gradual reduction in masseter thickness and volume, respectively, during the first 12 weeks.

That's also why I'd skip a top-up if one side looks different on day three. A review of non-response lists booster injections (retreatment within 3 weeks of the initial injection) among the trigger factors for a toxin later losing its effect.

In a phase 3 trial of onabotulinumtoxinA 72 U for a prominent jaw muscle, the authors reported effects lasting up to 6 months. That's a study result, not a calendar for your next trip.

Once you're home, if something looks off, such as one side looking fuller or a smile that feels stiff, you can send photos to the clinic's WhatsApp and ask. If the signs are significant, like trouble swallowing or breathing, see a local doctor or emergency care first.

The Bottom Line: Ask Per Side, Then Ask Where

• A 50U or 100U quote tells you little until you know whether it's per side or for both sides.

• The clench test comes first: Botox works on muscle, not on fat or bone.

• Units per side and placement matter every time; the product matters most after many rounds.

• Expect to fly home before the final result, and skip early top-ups.

Like any procedure, jaw Botox comes with trade-offs, and most of them are set by dose and placement. Ultimately, the choice depends on your face, your goals, and your travel dates.

Take one photo yourself before you message anyone: a side view with your teeth clenched. If the bulge is sharp and sits low at the jaw corner, your real question is units per side. If nothing changes when you clench, your question is whether Botox is the right tool at all.

If you're weighing masseter Botox in Seoul, Beautystone is a dermatology clinic in Hapjeong, one stop from Hongik University Station on Line 2. A first WhatsApp message could be: "I'm in Seoul from [date] to [date]. Attached are two side photos of my jaw, relaxed and clenched. My last jaw Botox was [product, units, date / never]. After an exam, could you tell me whether it's mostly muscle and how many units per side you'd suggest?"