Why can lip-corner Botox cause an uneven smile?
Asymmetry after lip-corner Botox usually happens because the effect reaches the lower-lip muscle next to the DAO, or because the left and right muscles were already different in strength. The treatment weakens the DAO, which pulls the corners down, to soften a downturned look. Just inside it is the depressor labii inferioris, which pulls the lower lip down to show the lower teeth. If that muscle is also weakened, one side of the lower lip moves less in a broad smile or certain sounds.
Common reasons include:
- Spread: an injection point placed too far inward or upward, or rubbing the area firmly right after treatment, can affect the neighbouring muscle.
- Pre-existing asymmetry: faces and expression muscles are naturally uneven; the same dose can produce different responses on each side.
- Dose: a large first dose can create a bigger change in movement.
- Treating nearby areas together: combining with chin (mentalis) Botox reduces overall lower-face movement, which can make the change more noticeable.
What symptoms can occur?
The most common is a crooked broad smile, with one side of the lower lip moving less; some people also notice awkward sounds or difficulty with straws or cups.
| Symptom | How it feels | Usual course |
|---|---|---|
| Uneven smile | Fewer lower teeth show on one side | Usually recovers as the effect fades |
| Speech change | Lip sounds such as "b", "p", "m" feel awkward | Usually adapts or recovers |
| Drinking or eating | Liquid seems to escape on one side | See the clinic if it is troublesome |
| Less corner movement | Expressions look less animated | Recovers as the effect fades |
Severity and recovery depend on dose, muscles and individual factors. The table shows general tendencies, not a guaranteed timeline.
How long does it last? Is it permanent?
Because botulinum toxin is temporary, asymmetry caused by its effect does not stay permanently; it generally recovers gradually as the effect wears off. Just as wrinkle treatments are usually described as lasting about 3–4 months, movement returns little by little over weeks. No exact date can be promised, and larger doses may take longer.
When and how is it corrected?
The principle is to assess real movement at about two weeks, when the effect is clearest, and choose a correction that matches the cause. There is no way to "remove" toxin that has already acted, so correction means waiting or balancing the two sides.
- Watchful waiting: if it is not very troublesome, letting the effect fade is the lowest-burden option.
- Topping up the weaker side: if one side simply responded less, a small top-up on that side may be considered after two weeks.
- Balancing the other side: if one side of the lower lip moves less, a small dose on the other side is sometimes considered to even things out. This reduces overall movement and does not suit every case, so it is decided carefully.
Adding injections before two weeks means judging before the full effect has appeared, which can lead to over-correction. Frequent top-ups at short intervals are also a known risk factor for resistance, so they are kept to a minimum — see how often should you get Botox?
Our principle is to examine any unexpected reaction after treatment and, where appropriate, explain touch-up or correction options. Our Botox consent form also states that the effect can be partly insufficient and that further correction is possible at the doctor’s discretion; the same form advises keeping routine treatments at least three months apart to lower the risk of antibodies (resistance).
How can the risk be reduced?
It cannot be eliminated, but assessment and a conservative plan reduce the chance.
- Check both sides first: smiling, talking and closing the lips are observed to note any existing asymmetry.
- A conservative first dose: start low and top up only if needed after the two-week check.
- Injection point: plan along the DAO's course near the jawline and away from the lower-lip muscle.
- Aftercare: do not rub or massage the area on the day.
- Share your history: if you had a similar experience after lip-corner or chin Botox before, tell us — it is the most useful information for planning.
For other areas, see Botox by area; for the product we use, see Coretox.
When should you contact the clinic straight away?
Do not wait for two weeks if:
- drinks spill and eating or drinking is difficult
- speech is affected enough to interfere with work or daily life
- there is marked swelling, pain or warmth suggesting infection
- very rarely, you notice difficulty swallowing or breathing, eyelid droop or general weakness — seek emergency care immediately
Summary
An uneven smile after lip-corner Botox is a real, possible side effect, usually from the effect reaching a neighbouring muscle or from existing differences between sides. Because the effect is temporary it usually recovers, but starting conservatively and checking at about two weeks before deciding whether to wait or correct is the safer approach. Course and recovery vary between individuals.