Jaw-slimming Botox, injected into the large chewing muscles at the angle of the jaw, is one of the most-requested treatments you won't find on any FDA label yet. That may change. In August 2026, the FDA accepted Allergan Aesthetics' application to add masseter muscle prominence to BOTOX Cosmetic's approved uses. Until the FDA acts, every masseter injection in the U.S. is off-label.
Here's what that means for you, what the application says, and what to ask before you book.
What the masseter treatment is
The masseter is the thick muscle you can feel at the back of your jaw when you clench your teeth. When it's large, it can make the lower face look wider or more square. Injecting a botulinum toxin relaxes the muscle, and over time a less-used muscle can get smaller, which is why people seek it for a slimmer jawline. Some people also seek it for clenching or grinding, which is a different question covered below.
Where the FDA stands
On August 4, 2026, AbbVie announced that the FDA had accepted for review its supplemental application for BOTOX Cosmetic "for the temporary improvement in the appearance of marked to very marked masseter muscle prominence (MMP) associated with masseter muscle activity in adults."
What the announcement says about the evidence:
•The application rests on two Phase 3 studies, M21-416 and M21-417, which the company says met their primary endpoints with statistically significant improvement in masseter prominence compared with placebo.
•The company says the safety profile "was consistent with established uses, with no new safety signals identified."
•Patient satisfaction: twice as many treated patients as placebo patients reported being "Very Satisfied" or "Satisfied."
Those are the company's descriptions of its own studies. The FDA hasn't ruled on them, and AbbVie's announcement doesn't give a decision date. If approved, BOTOX Cosmetic would be the first neurotoxin with this indication in the U.S. and would have five aesthetic indications.
Today, BOTOX Cosmetic is approved for the temporary improvement of four areas in adults: moderate to severe glabellar lines (between the brows), lateral canthal lines (crow's feet), forehead lines, and platysma bands (vertical neck bands). No botulinum toxin is FDA-approved for the jaw muscle.
What "off-label" means for you
A doctor may generally prescribe or use an FDA-approved drug for an unapproved purpose when they judge it medically appropriate. That's legal and common. The FDA's patient page on unapproved uses of approved drugs explains the difference: for an approved use, the FDA has reviewed the benefits and risks, and the label tells providers how to use the drug for that purpose. For an off-label use, it hasn't, and the label doesn't.
In practice, for masseter injections that means:
•No FDA-reviewed dose for the jaw. The label gives doses only for the approved areas. Units for the masseter are the injector's judgment.
•The label's warnings still apply. BOTOX Cosmetic carries a boxed warning that the effects of all botulinum toxin products may spread from the injection site, causing symptoms that can include muscle weakness, double vision, drooping eyelids, and difficulty swallowing, speaking or breathing, hours to weeks after injection. The label also says serious adverse reactions have been reported with unapproved uses of BOTOX, and that "The safety and effectiveness of BOTOX® for unapproved uses have not been established."
•Units don't convert between brands. The label says BOTOX Cosmetic units can't be compared with or converted into units of other botulinum toxin products. A Dysport or Xeomin dose for your jaw is a different number. See our Botox vs. Dysport vs. Xeomin comparison.
•Insurance won't cover the cosmetic use. Jaw slimming is cosmetic. See when Botox is covered by insurance.
Jaw slimming vs. TMJ and grinding
The pending application is for the appearance of a prominent masseter, not for jaw pain or grinding. The National Institute of Dental and Craniofacial Research says botulinum toxin type A is FDA-approved for some medical conditions "but not for TMDs" (temporomandibular disorders), and that study results for TMDs have been mixed. If your goal is pain, clenching or grinding, start with a dentist or physician who treats those conditions, not a cosmetic appointment. NIDCR's TMD page covers the evidence on treatments.
Who should do it
Who may legally inject neurotoxins, and under what supervision, depends on your state. See who can legally inject Botox. For an off-label area with no labeled dose, experience with the lower face matters more than usual. Ask how many masseter treatments the injector has done and how they decide on dose.
Product source matters too. A CDC report in October 2026 described three patients in Colorado who developed symptoms after injections of a botulinum toxin product not approved in the U.S. at a medical spa, which had bought it from an online supplier. Our guide to where med spas get their Botox explains how to check.
Questions to ask before you book
•Is this treatment off-label, and do you explain that in your consent form?
•Which product will you use, where does the clinic buy it, and is it FDA-approved?
•How many units, and why that number for my face?
•How many masseter treatments have you done, and can I see before-and-after photos of your own patients?
•What side effects do you see with the jaw, and what should make me call you or seek urgent care?
•If my real problem is clenching or jaw pain, should I see a dentist first?
What to watch for
The FDA's decision on the masseter application is the next milestone. If it's approved, the label will give a reviewed dose and safety information for the jaw for BOTOX Cosmetic specifically. Other brands would still be off-label for the jaw unless their makers get their own approvals. We'll update this article when the FDA acts.
This article is educational and does not constitute medical advice. Always consult a licensed medical professional for personalized recommendations.
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