An uneven smile is a known but uncommon side effect of masseter treatment. While most patients do not experience this, it is important to understand why it can occur and how the risk is minimised.

Why an Uneven Smile Can Happen

Masseter treatment involves placing a muscle relaxing product into the masseter muscles to reduce overactivity. In rare cases, a small amount of the product can migrate from the masseter into nearby muscles that help control facial expression during smiling.

The muscles most commonly involved are the risorius and zygomatic muscles, which play a role in lifting the corners of the mouth. If these muscles are affected, one side of the face may move less during smiling, creating an uneven appearance.

This side effect can happen to anyone, even with good anatomy and no prior facial asymmetry.

What an Uneven Smile Looks Like

If this occurs, patients may notice that one side of the mouth does not lift as much when smiling. The face appears asymmetrical during expression, while the face remains normal at rest.

This effect is temporary and does not affect sensation or overall facial function.

How Long Does It Last

Because masseter treatment is temporary, any associated side effects are also temporary. An uneven smile typically resolves as the product gradually wears off. This usually takes between one and three months, depending on the individual.

Reducing the Risk of an Uneven Smile

The risk of this side effect can be significantly reduced by choosing an experienced injector who has a detailed understanding of facial anatomy and precise injection technique.

Following aftercare instructions is also important. Patients are advised to avoid exercise for 24 hours after the procedure. This helps reduce the risk of product movement and allows it to remain localised within the masseter muscle.

Why Experience and Aftercare Matter

Proper placement, correct dosing, and appropriate depth of injection all play a role in minimising unwanted muscle involvement. An experienced doctor or nurse will tailor treatment to your facial anatomy and muscle strength.

Clear aftercare guidance further supports safe and predictable outcomes.

Final Thoughts

An uneven smile is an uncommon and temporary side effect of masseter treatment. While it can occur, most patients do not experience it. Choosing an experienced injector and following aftercare instructions greatly reduces the risk.

A consultation allows you to discuss potential side effects, understand your individual risk, and proceed with confidence knowing that any effects are temporary and manageable.