In short
- Botulinum toxin → movement lines. The ones that appear when you make an expression: frown lines, forehead lines, crow’s feet.
- Hyaluronic acid → volume and support. Folds, loss of projection, contour, lips, under-eye hollows from lack of support.
- 🔑 The practical test: look at yourself with your face still. If the line disappears when you do not move, it is dynamic. If it is still there, it is static.
- Over the years, a dynamic line ends up becoming static. That is why many real cases are a mixture, and why the two are sometimes combined.
- Hyaluronic acid is reversible; toxin is not: it cannot be “removed”, you wait for the effect to wear off.
- The effect of toxin lasts four to six months, on this practice’s experience. The literature does not have that duration well established.
- Toxin has, by some distance, the strongest evidence in the whole field: 65 randomised trials and nearly 15,000 participants.
- Not every line needs an injection. There are cases where the right answer is skin quality, surgery or doing nothing at all.
- Botulinum toxin is a prescription medicine: the indication and the administration are a doctor’s responsibility after an individual assessment. This page is for information.
They are the two best-known injectables and they are constantly confused, because people arrive at the consultation with the same sentence — “I want to get rid of this” — for two problems that have nothing to do with one another.
The difference is simple to grasp: botulinum toxin acts on the movement of a muscle, and hyaluronic acid restores volume and support. One takes strength out of an expression; the other fills a space. Choosing wrongly is not dangerous, but it is money thrown away: if your problem is volume, relaxing a muscle is not going to change it.
This page explains how to tell them apart, and also when the answer is neither of the two.
Each treatment has its own page: botulinum toxin and hyaluronic acid. This one is for deciding between them.
The question that settles everything
Stand in front of the mirror and keep your face completely still. No expressions, no frowning, no smiling.
- The line disappears, or nearly. It is a dynamic line: it exists because a muscle contracts. Botulinum toxin territory.
- The line is still there. It is static: it is etched into the skin, or there is a loss of volume underneath that draws it. Filler territory — or something else.
- You can see something, and it is much more visible when you move. This is the most common situation beyond a certain age, and it is a mixture.
That ten-second test settles most of the questions that come into the consulting room.
What each one treats
| Botulinum toxin | Hyaluronic acid | |
|---|---|---|
| What it does | Reduces the contraction of the muscle that folds the skin | Takes up space: restores volume and provides support |
| On which kind of line | Dynamic, the kind that appears when you make an expression | Static, and loss of volume or contour |
| Usual areas | Upper third: frown lines, forehead, crow’s feet | Middle and lower thirds: cheekbone, folds, lips, chin, jawline, under-eye hollows |
| When it shows | Not immediately: the effect sets in over days | Immediately, although there is swelling for the first 48 hours |
| Reversible | No. You wait for the effect to wear off | Yes, with hyaluronidase |
| What it is | A prescription medicine | An implantable medical device |
The nuance almost nobody explains
A dynamic line does not stay dynamic forever. A fold repeated thousands of times a year ends up leaving a mark that remains with the face at rest. It is why the same line may need one thing at thirty and another at fifty, and why the two are sometimes planned together: relaxing the movement that produces it and separately treating the mark that has already formed.
It also explains something people ask about a great deal: why toxin “works better” the earlier you start. It is not that it prevents ageing; it is that there is more to be done on a line that has not yet been etched than on one that is already established.
The three differences that count when deciding
Reversibility. Hyaluronic acid is broken down with hyaluronidase, so a result you are not happy with can be undone. Toxin cannot be withdrawn: its effect is temporary and you wait. In practice this weighs heavily on a first treatment, and in opposite directions: filler can be undone, but toxin wears off by itself.
Duration. Here it is worth being exact. The 2021 Cochrane review confirms that toxin reduces wrinkles in the first four weeks, but expressly notes that the duration of the effect is one of the gaps in the evidence: it is not well established in the literature. What we can give you is this practice’s own figure: the range we work with is four to six months, with individual variation depending on the area treated, the dose and the person. With filler, duration depends on the product, the amount and the area, and it can persist a good deal longer than is assumed: there are descriptions of an effect maintained at 18 months in the under-eye area.
The strength of the evidence. It is an unromantic and very useful criterion. Botulinum toxin for facial wrinkles has a Cochrane review that brought together 65 randomised trials and 14,919 participants. No other treatment in this field comes close: for comparison, all the published literature on polynucleotides in aesthetic medicine that a systematic review could gather amounted to nine studies and 219 patients. Something being more studied does not make it better for you; but knowing how much backing what you are offered has is part of deciding.
When it is neither of the two
This part matters as much as the rest, because people arrive assuming the solution is an injection, and it is not always.
- There is too much skin. An eyelid drooping from excess skin is not corrected with toxin. That is surgery: it is compared in blepharoplasty or hyaluronic acid for dark circles.
- The problem is the quality of the skin. Dull, thin skin with fine surface lines and uneven texture: that is neither muscle nor volume. It is approached through facial redensification.
- It is a sun line, not an expression line. Photoageing has a field of its own, and part of it is treated with laser rather than injectables.
- The expectation is a different face. No injectable does that, and anyone promising it is describing something else.
- There is no indication. Sometimes the right thing is not to treat, and saying so is part of the job.
Can they be combined?
Yes, and it is common where both things coexist: the expression line and the loss of support. What is not supported is combining as a matter of course. A 2025 systematic review of combined treatments in aesthetic medicine brought together 29 studies and described adverse effects in 15–30% of cases — erythema, bruising, nodules — with serious complications rare, and concluded that heterogeneous methods and small samples limit how far the published work can be relied on. Translated: combining should answer a reason in your particular face, not a fixed package.
Risks, briefly
Both share the local effects of any injection: bruising, swelling, discomfort.
With toxin, the most cited is a drooping eyelid: the Cochrane review concludes that treatment probably increases that risk. It is temporary, like the effect, but that is a matter of weeks and it is worth knowing beforehand.
With hyaluronic acid, the common problems are mild, and the serious one is uncommon but real: vascular occlusion, described on its own page, along with the lumps and asymmetries behind most follow-up consultations.
⚠️ And one warning that applies to both: a 2025 review of adverse effects of toxin and fillers notes that there is a publication bias in favour of successful results over adverse effects. What gets published does not fully reflect what happens.
Book an appointment
You can book your own appointment. Pick the day and time from the free slots in the diary, in a panel that opens right here, without leaving this page.
Frequently asked questions
Which one suits me if I have forehead lines?
It depends on whether they show with your face still. If they only appear when you raise your eyebrows, it is a movement line. If they are already etched at rest, the etched line means also assessing the state of the skin and the support in that area.
Can I have both at once?
It is done when there is a reason for each. What is not supported is doing it as a matter of routine: each product should answer an identified problem.
Which lasts longer?
Toxin, at this practice, is worked with in a range of four to six months. It is worth knowing that this is clinical experience and not a well-established figure in the literature: the Cochrane review expressly names the duration of the effect as one of the gaps in the evidence. With filler it depends on the product and the area, and it sometimes lasts longer than people think.
Can toxin be removed if I do not like it?
There is no antidote: the effect simply passes with time. Hyaluronic acid is reversible with hyaluronidase. It is a difference worth bearing in mind for a first treatment.
Which is safer?
Both have a good profile in trained hands, with different risks: with toxin, a drooping eyelid; with filler, the uncommon but serious risk is vascular compromise. What most affects safety is not the product but who injects it and with what knowledge of the anatomy.
Is it true that if I start young I will not get wrinkles?
Not exactly. Treating an expression line before it is etched gives a better result than treating it afterwards, but that does not halt ageing or prevent the lines that do not depend on movement.
I have dark circles — which of the two?
Probably neither, until we know what kind of dark circle you have: pigment, a hollow, a bag or thin skin are four different problems with different solutions. It is explained in the comparison on dark circles.
Can botulinum toxin be advertised?
Not as a consumer product: it is a medicine subject to medical prescription and advertising it to the public is restricted. That is why this page is informative, does not mention brands and does not promise results. The indication is established in consultation.
Sources
- Camargo CP, Xia J, Costa CS, Gemperli R, Tatini MD, Bulsara MK, Riera R. Botulinum toxin type A for facial wrinkles. Cochrane Database Syst Rev. 2021;7. Sixty-five randomised trials with 14,919 participants; treatment reduces wrinkles in the first four weeks and probably increases the risk of eyelid ptosis; the authors note gaps in the evidence on repeated cycles, the frequency of serious adverse effects and the duration of the effect. https://pubmed.ncbi.nlm.nih.gov/34224576/
- Tam E, Choo JPS, Rao P, Webb WR, Carruthers JDA, Rahman E. A Systematic Review on the Effectiveness and Safety of Combining Biostimulators with Botulinum Toxin, Dermal Fillers, and Energy-Based Devices. Aesthetic Plast Surg. 2025;49(10). Twenty-nine studies out of 1,237 identified, with samples of 10 to 350 subjects; adverse effects in 15–30% of cases (erythema, bruising, nodules) and serious complications rare; heterogeneous methods and inconsistent protocols limit reliability. https://pubmed.ncbi.nlm.nih.gov/39719485/
- Di Santis ÉP, Hirata SH, Di Santis GM, Yarak S. Adverse effects of the aesthetic use of botulinum toxin and dermal fillers on the face: a narrative review. An Bras Dermatol. 2025;100(1). Notes a publication bias in favour of successful results over adverse effects and calls for mandatory reporting of the latter. https://pubmed.ncbi.nlm.nih.gov/39616095/
- Lampridou S, Bassett S, Cavallini M, Christopoulos G. The Effectiveness of Polynucleotides in Esthetic Medicine: A Systematic Review. J Cosmet Dermatol. 2025;24(2). Nine studies of low and moderate quality with 219 patients in total, used here only as a point of comparison for the volume of evidence available. https://pubmed.ncbi.nlm.nih.gov/39645667/
Book your consultation
If you have done the mirror test and are still unsure, that is normal: most faces are a mixture. What settles the question is not more information, it is an examination at rest and in movement.
At the assessment we identify how much of what you see depends on movement, how much on volume and how much on the skin, and tell you which to start with — or whether it is better not to treat anything. Botulinum toxin is a prescription medicine and its indication is always established in consultation.
Clinical confirmation by the surgeon
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Last reviewed: 23 August 2026. This content is for information only and does not replace an individual assessment by a healthcare professional.
