Lip flip gone wrong: why, how long and what to do

A "lip flip" involves injecting very small amounts of botulinum toxin along the edge of the upper lip, into the muscle that surrounds the mouth, so that the lip turns out slightly and looks a little more visible¹. When the result does not match expectations or a problem appears, people often speak of a "lip flip gone wrong". This is one of the lip problems after a botulinum toxin injection described in studies. The problems described are mild and temporary. This page answers the seven questions people ask most often.

Why can a lip flip go wrong?

The orbicularis oris muscle runs all the way round the lips. It is the muscle that closes them, purses them and pushes them forward when you drink, whistle, kiss or pronounce certain sounds. A lip flip deliberately relaxes part of it. Depending on the dose and the site, three situations may be experienced as a failure:

• a lip that is too relaxed: difficulty drinking through a straw, whistling, blowing, a feeling of numbness in the lip. These are the side effects reported in published studies^1,2. In a trial on lines around the mouth, side effects were more frequent with the higher dose³, and a review reports excessive weakness around the mouth linked to the dose⁴;
• an uneven lip: one side turns out more than the other. In the lower face, lip asymmetry is the side effect most often described⁵;
• a result felt to be insufficient: a lip flip does not add volume. In a prospective study, the upper lip gained a little height, with no change in volume at all².

A lip flip is not an indication in the French product labels, which provide in aesthetic use only for frown lines and, depending on the product, crow’s feet and the forehead⁶: it is an off-label use, still little studied. A systematic review found only seven studies describing the technique¹.

How soon after the injection does the problem appear?

It appears as the effect of the toxin builds up. Side effects of botulinum toxin usually occur within the first week⁷. In the prospective study mentioned, the change in lip shape was measured at day 15². No source gives a timeframe of onset specific to lip flip problems.

How long does it last?

The problems described are short-lived. According to the review of published studies, difficulty whistling or drinking through a straw resolves within a few weeks¹. In the prospective study, all side effects, including numbness and functional limitation, resolved on their own in less than 30 days². The aesthetic effect of the toxin on the lip can last longer: in the trial on lines around the mouth, it persisted up to week 16 with the lower dose³. The page on how long botulinum toxin lasts explains what this duration depends on.

Is it reversible?

Yes. The effect of the toxin on the muscle is temporary: transmission between nerve and muscle is gradually restored⁸. The lip regains its former strength and shape as the effect wears off.

Is there a treatment?

No product reverses the effect of the toxin: the problem resolves on its own, usually within a few weeks^1,2. A marked asymmetry can sometimes be discussed with the doctor, who will judge after an examination whether it is better to wait. No massage or exercise has shown any effect in the sources we consulted.

What should you avoid?

• Do not ask for another injection to "compensate" before the effect has worn off: weakness can be made worse by another toxin injected before the effect of the previous one has gone⁷.
• Do not add other products to the lip in a hurry to mask the result; wait to discuss it during a consultation.
• Avoid straws and very hot drinks if your lip is numb and hard to control.

When should you see a doctor?

Talk to the doctor who performed the injection if you have trouble keeping liquids in your mouth or speaking clearly, or if the problem does not improve after a few weeks. Difficulty swallowing, a changed voice or difficulty breathing are not caused by a lip flip: they are warning signs that mean calling emergency services (15 or 112 in France, or your local emergency number).

A lip that stays crooked is covered on the page about uneven lips after an injection. If the injection was rather meant to show less gum, see the page on the overcorrected gummy smile.