The Lip Flip Revisited: What New Research Says About How It Works

A small 2026 study used three-dimensional imaging to measure what a "lip flip" actually does. In 17 women given a low dose of botulinum toxin type A above the upper lip, the visible height of the upper lip increased slightly at two weeks, while lip volume did not change, and most of the effect had faded by one to three months. The results suggest the lip flip is a subtle, short-lived change in muscle pull, not a way to add fullness.

Why this was studied

A lip flip involves a few tiny injections of a neuromodulator into the muscle that circles the mouth, called the orbicularis oris. The idea is that relaxing the edge of this muscle lets the upper lip roll slightly outward, showing a little more of the pink part of the lip. It has become popular on social media as a lighter alternative to filler, but surprisingly little research has measured what it does. Our article on lip flip versus lip filler compares the two approaches in general terms.

What the researchers did

The research team enrolled 17 women, average age about 40. Each received a very small total dose of botulinum toxin type A, split between two points on each side of the upper lip, placed a few millimetres above the lip border and away from the centre.

The team used three-dimensional facial imaging to measure upper lip height, the height of the skin between the nose and lip, and lip volume before treatment and at 15, 30 and 90 days. Participants also filled out a validated questionnaire about how they felt about the area around their mouth, and side effects were recorded.

What they found

• A small increase in visible lip height at 15 days, of less than half a millimetre on average. This was statistically significant but modest.
• A shorter distance between nose and lip at the same point, consistent with the lip rolling outward.
• No change in lip volume at any time point.
• Effects faded quickly. By 30 days, lip height was no longer significantly different from the start, and by 90 days it was essentially back to baseline.
• Participants felt more positive about the appearance of their mouth area on the questionnaire, and overall improvement ratings were favourable.

Every participant had at least one mild, temporary side effect. The most common was numbness or an odd sensation in the upper lip, reported by about half. Others noticed numbness in the mouth, local pain or general discomfort. All of these settled within a month without treatment. The study did not report drooling, speech changes or uneven smiles, though these are recognized possibilities with lip injections in general.

How strong is this evidence?

This is a small, single-group study with no comparison group, the kind usually rated as low-level evidence. It is useful because it used objective measurements rather than photographs alone, but several limits apply:

• Only 17 people, all women, took part.
• No control group received a placebo injection, so we cannot separate the true effect from expectations.
• Only one dose and technique were tested, and results may differ with other approaches.
• Movement was not assessed. Effects on smiling, speaking and drinking were not measured.

The authors describe the results as exploratory. They help explain how the lip flip works, but they do not show that it is better or worse than any other option.

What it means for you

If you are considering a lip flip, realistic expectations matter. Based on this study, the change is subtle, it does not add volume, and it may wear off within weeks rather than months. Some people are happy with a gentle, temporary change. Others, especially those hoping for fuller lips, may find it underwhelming.

People who may be better suited to a lip flip include those whose upper lip seems to disappear or curl inward when they smile. People who may not be good candidates include those who rely heavily on precise lip control, such as wind instrument players, singers or people who speak professionally, as well as anyone who is pregnant or breastfeeding, has a neuromuscular condition, or has an infection or cold sore in the area. Temporary effects such as difficulty drinking through a straw, mild lisping or a slightly uneven smile can occur with injections near the mouth. Our article on neuromodulator side effects explains these in more detail.

Results vary from person to person, and some people are better served by no treatment, by addressing lip dryness and sun protection, or by discussing other options.

Questions to ask at your consultation

• Is my lip shape the kind that tends to respond to a lip flip?
• How long should I expect the effect to last, given this research?
• Could this affect my speech, drinking or playing an instrument?
• Would a different approach better match what I am hoping for?

Frequently asked questions

Does a lip flip make lips bigger?

Not in this study. Lip volume did not change. The upper lip showed slightly more of its pink portion because the muscle relaxed, but the lip itself did not gain fullness.

Why does a lip flip wear off faster than forehead treatment?

The dose used around the mouth is very small, and this muscle is used constantly for talking and eating. The authors also suggest nearby muscles may compensate. Together, this likely explains why the effect is short-lived.

Is the numbness normal?

In this study, temporary numbness or altered feeling in the upper lip was common and settled within a month. If you notice significant weakness, difficulty closing your lips or problems eating and drinking, contact your clinic.

Small, careful studies like this help set realistic expectations for popular treatments. If you would like to talk about whether a lip flip or another approach suits your goals, HealthPark Medical Aesthetics can discuss it with you at a consultation.

Source

Germani M, Munoz-Lora VRM, Roschel P, Cotofana S. Lip flip revisited: clinical outcomes and neuromodulatory basis of upper lip eversion. Aesthetic Plastic Surgery, 2026. Read the study