Masseter Botox: what it is and who it may suit

What is the masseter, and why does it matter?

The masseter runs from just in front of the ear down to the angle of the jaw, and it is one of the main muscles you chew with. When you clench your teeth, the firm bulge you can feel in the lower cheek is this muscle. In people who clench often, during the day or in their sleep, it can become more prominent over time; in others it is simply strong and bulky by nature. The result can be a square, wide-looking lower face and a sense of tiredness in the jaw muscles.

Who might it suit?

• People who describe jaw muscle tension and fatigue alongside teeth clenching or grinding
• People whose masseter is clearly bulky on examination, so that the lower face looks wide because of the muscle
• Those who want to soften their facial contour without surgery, using a reversible approach
• People who have had masseter treatment before and notice it starting to wear off

A wide lower face is not always down to muscle. Bone structure, the salivary glands and fat can all contribute. During the examination I ask you to clench while I assess the muscle by hand; if the width is not largely muscular, masseter treatment is unlikely to meet your expectations, and that is something we should discuss from the outset.

Is it a complete solution for teeth clenching?

No. Clenching and grinding (bruxism) can have different causes, including stress, sleep patterns and the way your teeth meet. Masseter Botox reduces the force of the muscle's contraction and may help ease symptoms, but it does not remove the cause. If you have tooth wear, pain in the jaw joint, clicking or difficulty opening your mouth, a dental assessment is important, and measures such as a night guard may be needed. If you have significant jaw joint pain or locking, that assessment comes first.

Symptoms or appearance? Clarifying the goal

People come for masseter treatment with two different aims. Some come because of morning jaw fatigue, tension spreading to the temples or a clenching habit; others want the lower face to look slimmer and softer. Many have both. Being clear about the goal matters when deciding the dose and when to review. For someone coming purely for aesthetic reasons, the aim is a balanced reduction in muscle bulk; when symptoms are the main concern, the priority is to calm the overactive muscle. Either way, preserving normal chewing is essential.

The rest of the face is assessed too. In some people a prominent masseter makes the cheekbones and chin look weaker; once the muscle slims, the proportions of the face can read differently. Talking this through beforehand avoids surprises later.

How is it done?

1. Examination: the thickness and borders of the muscle, any differences between the two sides and your symptoms are assessed.
2. Planning: the dose and injection points are set separately for each side, according to the size of the muscle and your goal.
3. Treatment: each masseter is injected at a few points with a fine needle; the procedure is usually quick.
4. Review: a check-up a few weeks later is recommended to assess the effect.

When will I see the effect, and how long does it last?

Muscle relaxation and relief from clenching-related tension are usually noticed within the first 1–2 weeks. Slimming of the lower face is a slower process: as the muscle works less, it loses bulk, and for most people this change appears over a period of several weeks to a few months. The effect in the masseter often lasts somewhat longer than in other facial areas, but the exact duration varies with the individual, the strength of the muscle and the dose used. Intervals between repeat treatments are adjusted according to your physician's assessment. For general timing, see our article on when Botox starts working and how long it lasts.

If you are travelling to Istanbul for treatment, keep in mind that the slimming effect develops after you have gone home. The review can be done remotely using photos as part of follow-up for international patients.

Before and after treatment

Before treatment, it is important to tell us about any medicines you take — particularly blood thinners and certain antibiotics — and the dates of any previous toxin treatments. Never stop a prescribed medicine on your own; if an adjustment is needed, it should be discussed with the doctor who prescribed it.

• Do not massage or rub the area firmly on the day of treatment
• Avoid strenuous exercise, saunas and steam rooms on the first day
• Do not lie face down for a few hours after treatment
• Don't judge the result in the first two weeks, before the effect has settled
• If you wear a night guard, keep using it unless your dentist advises otherwise

At the review we look at how the muscle has responded, the balance between the two sides and any change in your symptoms. The timing of the next treatment is also agreed then, based on how long the effect has lasted.

Possible side effects and limits

Mild redness, tenderness or small bruises may appear at the injection sites. In the first weeks, chewing hard foods may feel temporarily tiring. Less commonly, unwanted effects such as an asymmetric smile have been reported, which is why the dose and injection points are chosen carefully. Pregnancy and breastfeeding, certain neuromuscular conditions and active infection in the treatment area are among the situations that rule out or postpone treatment.

How it relates to jawline treatments

Some people have both a prominent muscle and a lack of support at the chin or jaw angle. In that case masseter treatment can be planned in stages alongside jawline filler or chin filler. Usually we wait for the muscle to slim first, because it makes little sense to decide how much filler is needed before you can see the new balance of the lower face. We explain who may be a candidate for chin treatment in who is chin filler for?.