Botulinum toxin for expression lines: what the evidence shows

Dynamic lines only, and why that distinction is the most important thing to understand.
Well Established

Medically reviewed by:

Awating Review

Educational only, not medical advice · Prescription-only medicine

AT A GLANCE

Skin of colour: Safe across all tones, no chromophore and no PIH risk.

DOWNTIME

None

back to work same day

SESSIONS

One session

top-ups every 3-4 months

RESULTS

Onset 3-5 days

full effect about 14 days

DISCOMFORT

2-3 / 10

fine-needle pinpricks

PRESCRIPTION

POM

price cannot be advertised

Reversible? Yes. It wears off naturally, and no antidote is needed.

WHAT IT IS

A prescription medicine that quietens a muscle, not a filler

Botulinum toxin type A is an injectable prescription-only medicine that temporarily relaxes specific facial muscles so the skin above them stops creasing into expression lines.

It is given as a series of small, fine-needle injections at precisely mapped points. The injections themselves usually take 10 to 15 minutes. Allow 30 to 45 minutes in total, including the face-to-face prescribing consultation that has been a legal requirement in the UK since 1 June 2025.

UK-licensed brands for cosmetic upper-face use include Botox and Vistabel, Azzalure, Bocouture, Alluzience, Letybo, Nuceiva and Relfydess. That is a factual list of what exists. Brands are not ranked, compared or evaluated against one another on this site.

This page covers dynamic expression lines of the upper face only: frown lines, horizontal forehead lines and crow’s feet.

Other uses of botulinum toxin, including brow lift, masseter slimming and neck bands, have their own pages.

01 · Signal interrupted

SNAP-25 cleaved

The toxin cleaves SNAP-25, a protein the nerve ending needs in order to release its chemical messenger.

02 · Muscle relaxes

No contract signal

With no signal arriving, the targeted muscle relaxes. The effect is local and temporary. It does not travel through the body.

03 · Skin stops folding

Dynamic lines soften

The overlying skin is no longer folded repeatedly, so lines driven by movement gradually soften.

HOW IT WORKS

Like turning the volume down on a muscle

When you frown, squint or raise your brows, the muscles underneath pull the skin into folds. Do that thousands of times over years and those folds gradually become lines: first only when you make the expression, later etched in even when your face is still.

Nerves tell muscles to contract by releasing a chemical messenger called acetylcholine. Botulinum toxin blocks that release, so the muscle relaxes and the skin above it stops being creased. Nerve endings regenerate over weeks to months, which is why movement returns and the effect fades after three to four months, sometimes five.

One consequence matters more than any other. The frontalis muscle in the forehead is the only muscle that lifts the brows, which is why over-relaxing it can lower the brow and add heaviness. Treating the forehead conservatively, and always in balance with the frown complex, is a fundamental of good injecting.

A line that only appears on movement will soften. A line etched in at rest will improve partially, not disappear.

DEPTH OF ACTION

The needle delivers product into the muscle layer, where the nerve endings meet the muscle fibres. The skin surface is not resurfaced or heated, which is why there is no pigment risk in any skin tone.

STEP 1

Assess

A face-to-face prescriber checks your lines at rest and on movement, and looks for brow descent before anything is injected.

STEP 2

Inject

A series of fine-needle injections at mapped points. Ten to fifteen minutes, a brief sharp pinprick at each point.

STEP 3

Settle

Onset at three to five days, full effect at about two weeks. Judge the result then, not on day three.

THE HONEST CEILING

What it won't do

This treatment is genuinely well established for dynamic expression lines. Being clear about where that stops is the most useful thing this page can offer.

WHAT IT CAN DO

  • Soften frown lines, forehead lines and crow’s feet that are driven by movement
  • Make a face read as less tired, less tense or less cross
  • Modestly open the outer eye corner where hooding is driven by muscle pull
  • Work safely across every Fitzpatrick skin tone

WHAT IT CANNOT DO

  • Erase lines you can still see when your face is completely relaxed
  • Lift a brow that has genuinely descended, or remove excess eyelid skin
  • Improve skin quality, crepiness or sun damage
  • Replace a facelift or address jowling and lower-face laxity

BY CONCERN

Two concerns, two honest answers

This treatment serves more than one concern, and the honest answer is not the same for each. Each block below carries its own tier, its own evidence and its own ceiling, rather than one blended claim.

Frown lines, forehead and crow’s feet

Well Established

BOTULINUM TOXIN · UPPER-FACE EXPRESSION LINES

Aug 2026

This is the flagship indication and the best-evidenced non-surgical treatment for dynamic upper-face lines. An independent network meta-analysis (Li, Sui, Xia and Chen, 2023) compared multiple toxins and doses across all three upper-face areas and confirmed strong, reproducible responder rates. A pooled analysis of 1,678 participants across six placebo-controlled trials found significantly higher responder rates than placebo at four weeks.

Onset is three to five days, with peak effect at about two weeks and duration of three to four months. Strong or toxin-naive muscles may need more units, which is what the two-week review appointment is for.

The licensing picture is not uniform, and it is worth knowing. Frown lines are on-label for every UK-licensed cosmetic toxin. Crow’s feet are on-label for Botox and Vistabel, Bocouture, Azzalure and Relfydess. Horizontal forehead lines are on-label for Bocouture and Botox or Vistabel only. Treatment of the forehead with any other licensed brand is legal off-label use, but it should be explained to you first. Stating a product’s licensing status for an area is a regulatory fact, not a comparison between brands.

For lines with a significant static component, partial improvement is the realistic expectation. The dynamic contribution softens, the etched texture persists.

  • Li W, Sui X, Xia Y, Chen B. Network meta-analysis of botulinum toxin products for upper facial lines. Aesthetic Plastic Surgery, 2023;47(1):365-377. Not manufacturer-funded. An independent comparison across frown, crow’s feet and forehead areas confirming strong, reproducible responder rates across brands and doses.
  • Brin MF et al. Individual-patient-data meta-analysis of onabotulinumtoxinA for glabellar lines. Journal of the American Academy of Dermatology, 2009;61(3):486-492. Manufacturer-funded by Allergan and AbbVie, disclosed. Pooled 1,678 participants across six placebo-controlled trials and found a significantly higher responder rate than placebo at four weeks.
  • Brin MF et al. Safety and efficacy meta-analysis of 5,298 onabotulinumtoxinA-treated participants. JAAD International, 2024;14:4-18. Manufacturer-funded by Allergan and AbbVie, disclosed. The largest pooled safety dataset available; eyelid ptosis 1.1 percent, brow ptosis about 0.6 percent.
  • Carruthers JA, Carruthers A, Said S. Dose-ranging randomised controlled trial for glabellar lines. Dermatologic Surgery, 2005;31(4):414-422. Manufacturer-funded by Allergan and AbbVie, disclosed. Definitive dose-ranging data showing 20 to 40 units superior to 10 units, with three to four month duration.
  • Smith L et al. Great British and Northern Ireland Botulinum Toxin Survey. Aesthetic Surgery Journal Open Forum, 2025;7:ojaf115. Independent. In 919 respondents the most common acute complications were bruising and swelling at 26.1 percent and headache at 24.7 percent.
  • UK Summaries of Product Characteristics for all licensed brands, medicines.org.uk/emc, 2025 to 2026. Regulatory, not commercial. The canonical source for licensing by area and brand. Verify at publish, since new market entrants or label variations change this.

← Back to all options for upper-face expression lines

HOODED OR HEAVY UPPER EYELIDS

Lateral hooding: modest, and only one pattern

Well Established

This is a more nuanced indication than straightforward line softening, and the distinction matters before you book.

Careful placement along the outer border of the eye socket relaxes the muscle fibres that pull the brow downward and hood the outer eyelid. That can open the outer corner of the eye by a few millimetres. It works for the specific pattern of lateral hooding driven by muscle pull, and is usually combined with crow’s feet treatment because the injection points overlap.

It cannot lift a brow that has genuinely descended with age, and it cannot address excess upper-eyelid skin, which is surgical territory. If the eyelid skin touches the lash line at rest, or the heaviness comes from the brow sitting well below the bony ridge, this will do little and may make things worse by relaxing a forehead that was compensating.

A good practitioner separates three things at consultation: muscle-pull hooding that responds, brow descent that does not, and excess eyelid skin that needs surgery. They look similar and are treated very differently. Ask which one applies to you.

A targeted chemical brow lift is a different technique with its own injection map and its own page.

  • Brin MF et al. Safety and efficacy meta-analysis, 5,298 participants. JAAD International, 2024;14:4-18. Manufacturer-funded by Allergan and AbbVie, disclosed. Includes lateral canthal data supporting the on-label position for several brands in this area.
  • Li W et al. Network meta-analysis of upper facial lines. Aesthetic Plastic Surgery, 2023;47(1):365-377. Not manufacturer-funded. Includes crow’s feet as a primary area, with results consistent with the frown-line evidence.
  • UK Summaries of Product Characteristics, lateral canthal lines by brand, medicines.org.uk/emc. Regulatory. On-label for Botox and Vistabel, Bocouture, Azzalure and Relfydess. Off-label but legal, and to be disclosed, for Alluzience, Letybo and Nuceiva. Verify at publish.

← Back to all options for hooded or heavy upper eyelids

SAFETY AND THE LAW

Three things that are not optional

Botulinum toxin is a prescription-only medicine, and the rules around it exist because people have been harmed. These are not small print. If a clinic does not meet all three, walk away.

Insist on a face-to-face prescriber, a named UK-licensed brand, and a regulated clinical setting.

01 · Under 18

A criminal offence

It is a criminal offence in England to administer botulinum toxin for cosmetic purposes to anyone under 18, or to arrange for it to be administered. This applies regardless of parental or patient consent, and regardless of the circumstances of the appointment. The Botulinum Toxin and Cosmetic Fillers (Children) Act 2021 came into force on 1 October 2021. Consent is not a defence.

02 · Prescribing

Face to face since June 2025

Since 1 June 2025 a prescriber must assess you in person before prescribing botulinum toxin for cosmetic purposes. Remote or online prescribing is not permitted, and this applies to doctors, nurses, dentists and pharmacist independent prescribers alike. Any clinic offering to prescribe without seeing you in person is operating unlawfully. The consultation is the safeguard: it is where brow descent is caught and where the dynamic versus static distinction is actually assessed.

03 · Unlicensed product

The 2025 outbreak

In 2025 England saw an outbreak of iatrogenic botulism linked to unlicensed product and specific practitioners. UKHSA recorded 41 clinically confirmed cases across five regions, with 32 hospitalised and 8 requiring intensive care. A case-control investigation found cases were significantly more likely to have received an unlicensed product, with seized vials testing at 370 units against a 200-unit label. This was driven by unlicensed product and unqualified injectors, not by licensed toxin correctly administered. Verify current case counts at publish.

SKIN OF COLOUR

Safe across all skin tones, and the mechanism explains why

Botulinum toxin type A is safe across every Fitzpatrick skin tone. The toxin contains no chromophore and involves no heat, no light energy and no trauma to the skin surface, so there is no mechanism by which it causes post-inflammatory hyperpigmentation or thermal injury. Injection-site bruising is the commonest skin-relevant complication and it is not tone-dependent.

This is a genuine advantage over many of the alternatives used for the same upper-face concerns. Ablative laser resurfacing, deep chemical peels and IPL all carry real pigmentation and burn risk in Fitzpatrick IV to VI and need careful settings and experienced operators. Toxin carries none of that risk for the muscle-relaxing job it does.

Where skin tone does become relevant is if toxin leads you toward resurfacing for the remaining static lines. That is the point to seek a practitioner with documented experience treating your skin tone, and to ask about test patching and conservative initial protocols. Those questions belong to the resurfacing conversation, not this one.

One honest note on the evidence itself. The Great British and Northern Ireland Botulinum Toxin Survey recorded that respondents were predominantly white and female. That reflects who currently accesses these treatments, not a biological difference in how toxin works across tones.

I
Safe, no restrictions
II
Safe, no restrictions
III
Safe, no restrictions
IV
Safe, no restrictions
V
Safe, no restrictions
VI
Safe, no restrictions
△ Risk is not zero. Bruising happens in any skin tone, and unlicensed product carries risks that have nothing to do with pigment.

RESULTS TIMELINE

What you’ll see, and when

Nothing happens on the day, and that is expected. The effect arrives gradually over two weeks and then fades over months. Judge the result at peak, not at day three.

WHAT PEOPLE TEND TO REPORT

The overall picture

Reports on upper-face toxin are broadly positive, and they share a consistent register: people describe still looking like themselves, just less tired or less cross. Where it lands well or badly turns on the injector’s skill and on what kind of line is being treated. The honest ceiling shows up clearly in patient discussion. Lines that move soften well, but deep lines etched in at rest do not vanish however much is injected, and undoing them takes time and usually other treatments alongside.
What people consistently say works

The recurring satisfaction is subtlety. People describe a natural result that others cannot quite place, reading calmer and more approachable, particularly on video calls where the face does a lot of talking. First-timers regularly say the anxiety beforehand proved unfounded, and the appointment far less of an ordeal than they had imagined.

Where it disappoints, and why

Deep frown lines that stay visible at rest, even when the forehead and crow’s feet respond well. That is the honest ceiling doing its work: an etched line needs time and consistent treatment to fade, and often resurfacing alongside, not a bigger dose chasing a flat result. The other recurring letdown is technique, an over-frozen look or a heavy brow, usually where the forehead was treated without the balance of the frown area.

What catches people out

A temporary heavy brow or slight unevenness in the early weeks, which resolves. Mild bruising. And duration: people are regularly surprised that the first treatment wears off sooner than they expected, with longevity tending to build over subsequent rounds rather than being fixed from the start.

What people wish they’d known

Some younger patients, looking back, question whether they needed it yet at all. Waiting is a legitimate choice, and a good practitioner will say so. If deep lines at rest are your concern, ask upfront what toxin alone can and cannot do for them. And ask directly which product is being used and who is prescribing it.

Anecdotal, drawn from publicly available patient discussion across review platforms and UK forums. Not clinical evidence and not an endorsement. No clinics are named. Individual experiences vary.

FREQUENTLY ASKED QUESTIONS

Questions people always ask

Will it get rid of lines I can already see when my face is relaxed?
Not fully. Botulinum toxin relaxes the muscle that drives a line, so a line that mostly vanishes at rest will soften well. A line that stays clearly visible when your face is completely still is an etched static line. Toxin will reduce the dynamic part of it but will not erase the texture. Static lines need resurfacing treatments and time.
No. If expression lines only show when you are moving your face and do not distress you at rest, observation and daily SPF are the evidence-supported first step. Starting in your twenties because you have heard it is preventative is a plausible but unproven rationale. The evidence for long-term prevention is a single twin observation, not a controlled trial. There is no clock forcing a start date, and a good practitioner will tell you that.
Onset is three to five days, with full effect at around two weeks. Most people find results last three to four months, sometimes up to five. Plan for roughly three sessions per year. First treatments sometimes fade faster, and duration often settles with subsequent appointments.
No. It is temporary and almost always resolves as the toxin wears off over a few weeks. A slightly uneven brow can often be corrected with a few extra units at your two-week review. If you have a heavy feeling over one eyelid, brow-lift eyedrops can help while you wait. Any change in vision is different, and you should seek care urgently for that.
Treat very low prices with significant caution. Under-dosing, which both underperforms and fades fast, unlicensed or counterfeit product, and unqualified injectors are the factors that produced the 2025 botulism outbreak. A named UK-licensed brand and a face-to-face regulated prescriber are the minimum requirements, and they are harder to provide at very low price points.
Yes. Botulinum toxin carries no chromophore and no thermal risk, so it is safe across all Fitzpatrick skin types. There is no pigmentation risk from the toxin itself. Where skin-tone caution becomes relevant is with the alternative treatments for static lines, such as ablative laser and deep peels, not with this treatment.
Biologically plausible, but not proven by controlled long-term evidence. The most-cited reference is a single twin study, not a trial. Treat preventative claims as a reasonable hypothesis rather than an established benefit. If you are making treatment decisions based on prevention, understand that you are working in the absence of proof, not with it.
Not with conservative, well-planned dosing. The goal is softer movement, not the absence of it. A frozen appearance results from over-dosing, wrong patient selection, or both. If you see a heavily motionless result in a practitioner’s portfolio and it concerns you, say so.
Yes. Men often have stronger facial muscles and typically need higher unit counts to achieve the same softening. That is a dosing consideration, not a contraindication. The two-week review is particularly important for first-time male patients, as initial dosing is often deliberately conservative.
It depends which product your practitioner uses. Horizontal forehead lines are on-label only for Bocouture and Botox or Vistabel in the UK. Treatment with any other brand is legal but off-label, and this should be disclosed to you before the injection. Ask which product they plan to use and whether it is on-label for the area being treated.

RELATED CONCERNS

Upper-face expression lines →
Hooded & heavy upper eyelids →
Neck lines & sagging →
Jawline, jowls & double chin →
Excessive sweating →
Medical review · Dr Priya Verma
Educational only; not medical advice. Evidence tiers reflect our reading of the weight of published evidence plus real-world signals, not a ranking of any product, device, clinic or practitioner. Botulinum toxin softens dynamic expression lines driven by movement; it does not erase lines etched in at rest, lift a descended brow, remove excess eyelid skin or improve skin quality. This page covers dynamic upper-face lines only. Botulinum toxin is a prescription-only medicine: under the Human Medicines Regulations 2012 its price cannot be advertised to the public, and no price or booking is shown here. It is a criminal offence to administer it for cosmetic purposes to anyone under 18. Since 1 June 2025 a prescriber must assess you face to face before prescribing. Regulatory positions are current to 2026 and must be verified at the point of treatment.