Jawline slimming in Hanoi, performed by our doctor

When a wide jaw is about the muscle

The chewing muscle at the angle of the jaw is called the masseter. In some people it is large, and it gives the lower face a square or wide look. Muscle-relaxing injections soften that muscle, and as it relaxes the width can slim. A 2026 analysis of five randomised trials (536 people) found the injections improved masseter prominence compared with placebo, but the size of the change varied between studies and the follow-up was short.

A wide jaw can also come from the bone or from fat under the skin, and the injections change neither. The doctor feels the muscle while you clench, and tells you whether treatment is worth it for your face.

Tell the doctor if you clench or grind your teeth or have jaw pain. People who clench or grind may need more sessions to reach the result they want.

What the session is like

A few small injections into the muscle on each side of the jaw. The injections themselves take a few minutes; most of the appointment is the consultation before it.

You can go back to your day straight afterwards. The change is gradual, because the muscle softens slowly. Studies usually judge it around three months after a session, and it is not permanent, so the muscle recovers and sessions are repeated to keep the change. The doctor will tell you what to expect for your face rather than give a date.

After the session

For the first 12 hours, do not rub or massage the treated areas, and stay upright for three to four hours. Our usual advice is to skip saunas and hard workouts for 24 hours, mainly to keep bruising down. You get written aftercare for the areas you had done.

Some people find chewing feels weaker for a while. Studies describe this lasting from several weeks to about three months, and it settles as the muscle recovers.

If you are in Hanoi for a short stay, book early in your trip so the result has time to settle before you leave.

Who it suits

It suits a lower face that looks wide or square because of the muscle, and people who want a softer jaw line without surgery. If the skin along the jaw is already loosening, slimming the muscle can make that more noticeable, so the doctor may suggest a lifting treatment such as HIFU instead.

• A jaw that looks square, with a muscle you can see or feel bulging when you clench
• A face that is otherwise in proportion, where the lower third is the part that feels heavy

When it is better to wait

Some antibiotics and muscle relaxants can strengthen the effect, so tell us about every medicine you take.

Tell us first, and expect to be asked to wait, if any of these apply:

• You are pregnant or breastfeeding.
• You have a condition that affects your muscles or nerves, such as myasthenia gravis.
• There is an infection or broken skin on the area.