Masseter Botox Gone Wrong: What Actually Causes It
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I'm Dr. Jong Seon Kim, a plastic surgeon at Gangnam HERA in Seoul. Patients send me photographs asking whether something has gone wrong after masseter botox more often than they ask about any other injectable. It is a fair worry, and it deserves a straight clinical answer rather than reassurance.
What does "masseter botox gone wrong" usually mean?
In most cases it means the dose or the placement was wrong — not the product. The masseter is a large muscle with a clear border, and the muscles around it do very different jobs. Product that drifts outside that border reaches muscles used for smiling or chewing, and that is where the visible problems come from.
The three problems patients actually describe
An uneven or crooked smile
This happens when product reaches the risorius or zygomaticus — the muscles that pull the corner of the mouth. It is a placement issue, not a dosing one, and it resolves as the effect wears off.
A sunken or hollow lower face
Over-treatment. The masseter is a working muscle; reduce it too far or too often and the cheek loses support. This is the one I see most in patients who kept topping up while chasing further slimming.
Chewing fatigue that lingers
Normal in mild form during the first weeks. Persistent, marked weakness suggests the dose was higher than the muscle needed.
Why it is avoided in the first place
By mapping the muscle before injecting. I ask you to clench so the border is palpable, then keep product inside it and at the right depth — the masseter is deep, and superficial placement is exactly how neighbouring muscles get involved. Dose follows the muscle I can feel rather than a fixed menu.
At HERA this is physician-injected, and we follow a genuine-product protocol with opening, serial and record handling so you can verify what was used.
What to do if it has already happened
First: it is temporary. Botulinum toxin wears off, generally over three to four months, and asymmetry resolves with it. There is no dissolving agent as there is for filler, so the honest answer is time — plus, where it helps, adjusting the untreated side rather than adding more to the treated one.
Bring the details if you have them: which product, how many units, which date. That changes what I can safely do today.
What patients ask me next
"Was it a fake product?"
Usually not. Technique explains far more of these cases than counterfeit product does, though genuine-product handling is something you should still be able to verify anywhere you are treated.
"Will it happen again if I retreat?"
Not if the cause is identified. I would rather start conservatively on a corrective visit and review you than repeat the dose that caused the problem.
What to ask before you let anyone inject
Most of the corrections I am asked to make could have been avoided by three questions at the first consultation. I would rather patients ask them of me too.
- "Will you palpate the muscle before injecting?" If the plan is made from a photograph alone, the border is being guessed.
- "What dose, and why that dose for my muscle?" A number quoted before examination is a menu price, not a clinical decision.
- "What is the follow-up plan?" A conservative first dose with a review beats a large single session — you can always add, you cannot subtract.
Why "you can always add" matters here
Filler can be dissolved. Botulinum toxin cannot. That asymmetry is the whole argument for starting low in a muscle you use every day to chew, and it is the reason I decline requests to "do more this time so it lasts longer".
The honest limits
No injector can promise zero variation — the same units in two faces behave differently. What can be promised is a plan based on the muscle you actually have, a conservative first dose, and a follow-up rather than a bigger single session. If anyone offers you a guaranteed outcome for a muscle they have not palpated, be careful.
The clinical detail — who it suits, how a session runs, recovery and the honest limits — is set out on our Allergan Botox page.
Book a consultation
If you would like me to assess your jaw, send us a message. We will arrange a consultation in Gangnam, or a photo consultation first if you are still abroad. An English interpreter joins every visit, and you receive an itemised written estimate before anything begins — international and local patients pay exactly the same.
FAQ
Frequently asked questions
Q1What usually causes masseter botox to go wrong?
Dose or placement, not the product. The masseter is deep with a clear border; product that drifts outside it reaches muscles used for smiling or chewing, which is where visible problems come from.Q2Why does my smile look uneven after masseter botox?
Product likely reached the muscles that pull the corner of the mouth. It is a placement issue and it resolves as the effect wears off, generally over three to four months.Q3Can masseter botox be reversed?
There is no dissolving agent as there is for filler. The honest answer is time — botulinum toxin wears off — plus adjusting the untreated side where that helps, rather than adding more to the treated one.Q4Why does my lower face look hollow?
That is usually over-treatment. The masseter is a working muscle; reduced too far or too often, the cheek loses support. It is most common in patients who kept topping up chasing further slimming.Q5Is chewing weakness normal?
Mild fatigue with hard foods in the first weeks is normal. Persistent, marked weakness suggests the dose was higher than the muscle needed.
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