Masseter Botox Left Hannah Berner Unable to Smile: What Went Wrong

Comedian Hannah Berner told the New York Times that a routine Dysport appointment at a new office left her unable to smile for weeks. That single complication story has pushed masseter Botox — one of cosmetic dermatology's most-requested injectables — back into the risk conversation.

The treatment slims square jawlines and eases the clenching tied to stress, grinding and TMJ disorder. Nearly 11 million Americans live with temporomandibular disorder, the jaw condition driving much of that demand. But Berner's case shows what happens when placement misses its mark in a crowded anatomical neighborhood.

How does masseter Botox actually work?

The masseter muscles run along the back of the jawline. They do the heavy lifting when you chew, bite down or clench. Overused — often from stress-induced grinding — they thicken and widen the lower face, Beverly Hills plastic surgeon Daniel Gould told Women's Health.

The injections use botulinum toxin, sold under the brand names Botox, Dysport, Xeomin, Jeuveau and Daxxify, to relax that muscle bulk.

"Masseter Botox involves injecting botulinum toxin into the masseter muscles, which are the large muscles located at the sides of the jaw," Dr. Ahmed El Muntasar, founder of The Aesthetics Doctor clinic, told Who What Wear. "The treatment works by relaxing these muscles, helping to reduce excess tension and muscle bulk. As a result, it can reduce clenching, teeth grinding, jaw tension and tension-related headaches, whilst also softening the overall strength and size of the muscle over time."

In plain words: the toxin shrinks the workhorse muscle, and the jaw narrows with it.

Who is the right candidate?

El Muntasar described the ideal patient as someone with "large or overactive masseter muscles" — usually a grinder, a clencher or someone whose jaw locks. Aesthetically, the payoff is a softer, more tapered, V-shaped lower face.

Not everyone gets that result. Patients whose jaw shape doesn't come from muscle bulk, or who carry meaningful skin laxity, can see jowling worsen as the muscle shrinks.

"The masseter muscle provides some underlying support to the lower face," El Muntasar said. "Reducing its bulk in patients who already have skin laxity can accentuate jowling or lower-face sagging. This is why careful patient selection, conservative dosing and a full facial assessment are essential."

Selection, not injection speed, is where good outcomes start.

What does the appointment involve?

The technique mirrors standard Botox, but the dose runs larger because the muscle does. The average is 12 to 24 units per side, said Lesley Clark-Loeser, a Davie, Florida dermatologist quoted in Women's Health.

"For the most part, the technique is the same, but when treating patients for jaw pain relief from clenching, we usually use more units as those muscles are larger," Clark-Loeser said.

A typical visit breaks down simply:

• Consultation and jawline cleanse
• Mapping with a white eyeliner pencil
• Three to four quick injections per side with very thin needles
• An ice pack afterward

Providers generally advise avoiding alcohol, blood-thinning pain relievers and supplements such as ginkgo biloba, ginger and vitamin E for several days before and after, to limit bruising.

What went wrong in Berner's case?

Results near the mouth are not always predictable. Boston plastic surgeon Dr. Sean Doherty told Yahoo that the masseter is not a smiling muscle, but "muscles on the lower face are intimately connected," so weakening one can throw off the others. Too much product, or product placed slightly off target, can migrate into muscles that control the mouth.

The likely culprit in cases like Berner's is the risorius, a nearby muscle involved in smiling, Omaha dermatologist Joel Schlessinger told New Beauty. The surrounding anatomy leaves little room for error, which is why injector experience with this specific area matters more than general Botox credentials.

And unlike filler, neurotoxin cannot be dissolved. Effects wear off over three to four months as muscle movement returns.

What should patients ask before booking?

The treatment is generally safe and widely performed, but the margin for error is real. Patients should vet the injector with specific questions:

• How many masseter cases do they do a month?
• How do they decide dosing for your specific jaw anatomy?
• Where exactly do they place injections to avoid the risorius and other smile muscles?
• What side effects have they seen tied to this area?

Timing matters too. Schlessinger advised against booking within a week or two of a major event, because recovery from any misstep takes time. "If someone is going to be at a very significant event, like a wedding or reunion, it isn't a great idea to get the masseters done within a week or two before it," he said. "It generally resolves, but can take a little time."

With conservative dosing, careful patient selection and an injector who works on the masseter routinely, the odds of an outcome like Berner's stay low — and the field's growing caseload suggests the demand that created that scrutiny isn't going anywhere.