Anti-wrinkle injections: how long they last and the risks
How anti-wrinkle injections work on frown lines, forehead lines and crow's feet, how long the effect lasts, the risks and who they are not suitable for.
5 min readEducational content by RejuvelookUpdated in October 2026
In short
Anti-wrinkle injections are prescription medicines that temporarily relax the muscles behind forehead lines, frown lines and crow's feet. The effect starts within a few days and is temporary: it wears off gradually over the months. In medical hands they are safe, but there is no antidote, so a careful dose matters.
Key points
- They treat lines that appear with movement, not sagging or lost volume.
- The effect is temporary, and how long it lasts depends on the dose, the muscle and the person.
- Men usually need higher doses, often double between the brows.
- A drooping brow or eyelid is uncommon and temporary, and depends on where and how deep the injection is placed.
- There is no antidote: if you dislike the result, you have to wait for it to wear off.
Forehead lines, frown lines and crow's feet are caused by repeated muscle movement. They are treated with a group of injectable medicines that relax those muscles for a while, known in medicine as neuromodulators and more widely as anti-wrinkle injections. You may know them by a brand name from home. You will not see one here: Spanish law does not allow prescription medicines to be advertised to the public, and in any case the name matters less than the indication, the dose and the technique.
What anti-wrinkle injections are and how they work
They are prescription medicines that temporarily block the signal between nerve and muscle. The treated muscle contracts less, so the skin above it creases less and the line softens. Over time the nerve restores the connection and the muscle moves again. That is why the effect is reversible and needs repeating.
Not everyone responds in the same way. The product, the dose, how many points are injected and where, muscle bulk and individual factors all play a part [1]. Men, for example, usually need higher doses: between the brows, often double the dose used in women [4].
Which lines improve, and which do not
They work on dynamic lines, the ones that appear when you make an expression:
- Horizontal lines across the forehead.
- Vertical frown lines between the brows, which can make you look cross or tired.
- Crow's feet at the outer corners of the eyes.
They are also used for other indications, such as neck bands, an uneven smile or excessive sweating, always after a specific assessment.
They do not treat sagging, lost volume or folds that are visible at rest because support has gone, such as the lines from nose to mouth. Deeply etched lines improve only partly and sometimes need combining with other treatments, such as hyaluronic acid or collagen stimulators.
How you are assessed and what the procedure involves
The doctor studies your face at rest and in movement: how you frown, how you raise your brows, how you smile. Not every frown works in the same way. The doctor also looks at the position of your brows and eyelids, any asymmetry and previous treatments.
The session takes a few minutes. Small amounts are injected with a very fine needle into specific points of each muscle. Anaesthetic is not usually needed. Small marks may remain for minutes to a few hours. A review at two weeks is standard, so the result can be fine-tuned if necessary.
How long do anti-wrinkle injections last?
You start to notice the effect after a few days. It is temporary: movement comes back gradually over the months, which is why treatment is repeated periodically.
How long it lasts depends on the dose, the muscle and the person [1]. At your review, your doctor will tell you how often it makes sense to repeat it.
What to expect, realistically
- A smoother forehead and frown area, with your expression kept if the dose is right.
- Dynamic lines much softer; lines etched at rest, only partly.
- A rested look, not a different face.
- A temporary effect that needs maintaining.
The frozen look is not inevitable. It usually comes from high doses or from treating muscles that did not need it.
Risks, and who it is not for
Used for aesthetic purposes by doctors, these medicines have an extensive safety record, and serious side effects are rare [2]. Most effects are mild: small bruises at injection points or a headache for the first day or two.
The best-known unwanted effects depend on anatomy and technique. A drooping brow mostly happens when injections are placed too low on the forehead. A drooping eyelid is linked to injecting too deep near the eye. An uneven smile can occur if the product reaches mouth muscles that were not meant to be treated [3]. These effects are temporary and resolve as the treatment wears off. For a drooping eyelid, there are eye drops that can improve its appearance in the meantime [2].
Less often, some people stop responding because they develop antibodies. This is linked to known risk factors such as high doses and frequent top-ups, which is why the intervals between treatments should be respected [2].
One thing worth knowing before you start: there is no antidote that reverses the effect. If you dislike the result, you have to wait for it to wear off. That is why a careful dose matters so much.
They are not recommended in pregnancy or while breastfeeding, with neuromuscular conditions, with an infection in the area or with an allergy to any of the ingredients. Some medicines can interfere, so tell the doctor what you take. And they should never be bought online or injected outside a healthcare setting: they are prescription medicines.
How we approach it at Rejuvelook
At our clinic in Fuengirola, treatment for expression lines always starts with a medical consultation. We study how your face moves, choose the points and dose with care, and review the result at two weeks. The aim is for you to look rested while keeping your expression. If your lines would respond better to a different treatment, we will explain why. We see patients in English or Spanish.
Before choosing where to have treatment, our guide on how to choose an aesthetic clinic in Spain may help.
What the evidence says
Each statement shows its level of evidence and the sources behind it.
Supported
- Used aesthetically by doctors, these medicines have an extensive safety record; serious side effects are rare.[2]High-quality evidence
With caveats
- The effect is temporary and how long it lasts varies with the dose, the muscle and the person.[1]Moderate evidence
- A drooping brow or eyelid and an uneven smile are linked to the injection point and depth.[3]Moderate evidence
- Men usually need higher doses because of greater muscle bulk.[4]Moderate evidence
Not enough support
- Starting very young to prevent lines: long-term studies showing a clear benefit are lacking.Low-quality evidence
When to see a doctor
Book a medical consultation, or go to A&E if it is severe or sudden, if you notice:
- A drooping eyelid or brow, double vision or a marked asymmetry in the following days: let the clinic that treated you know.
- Difficulty swallowing, speaking or breathing after treatment: call 112.
- A severe headache that does not ease, or a fever, after treatment.
- Redness, heat or a painful lump at an injection point.
Frequently asked
Does it hurt?
Very little. A very fine needle and small amounts are used, and most people describe it as a few quick pricks. Anaesthetic is not usually needed.
Can I go straight back to work?
Yes. Small marks may be visible for a short while. For the first few hours, avoid lying down and rubbing the area, and skip hard exercise, saunas and strong heat until the next day.
When will I see the result?
It starts to show after a few days. That is why the review is at two weeks, when it is possible to judge whether any adjustment is needed.
Can I have it before a holiday or a trip home?
Yes, with some margin. Ideally have it two to three weeks before, so the effect is complete and there is time for the review. Flying afterwards is not a problem.
If I stop, will my lines get worse?
No. When the effect wears off, the muscle moves normally again and your lines return to their natural course. There is no rebound effect.
Can it be combined with filler or other treatments?
Yes. It is often combined with hyaluronic acid for folds or with skin quality treatments. The doctor decides the order and whether to do them in the same session.
How often will I need it?
When you notice movement coming back; your doctor will tell you the right interval for you. It is best not to repeat too early or have frequent top-ups, because that raises the risk of no longer responding.
References
Sources checked against PubMed or Crossref. Cited as plain text, without links.
- 1.Chaudry A, DeVries A, Lam W, Lawson A, Nestor MS. Neuromodulators for Facial Aesthetics: Key Clinical Postulates. J Craniofac Surg. 2026. doi: 10.1097/SCS.0000000000013067. PMID: 42301245.Verified on 2 October 2026
- 2.Carruthers J, Fabi S, Kane M, Solish N, Dayan SH. Management and Prevention of Neuromodulator Complications. J Drugs Dermatol. 2025;24(1):7-11. doi: 10.36849/JDD.8355. PMID: 39761146.Verified on 2 October 2026
- 3.Cotofana S, Alfertshofer M. [Treatments with neuromodulators : Anatomical principles, mechanisms of action, and safe utilization in aesthetic medicine]. Dermatologie (Heidelb). 2026;77(3):152-157. doi: 10.1007/s00105-025-05628-4. PMID: 41469806.Verified on 2 October 2026
- 4.Minokadeh A, Matarasso SL, Jones DH. Neuromodulators in Men. Dermatol Surg. 2024;50(9S):S70-S72. doi: 10.1097/DSS.0000000000004336. PMID: 39196837.Verified on 2 October 2026
Educational content. It does not replace a medical consultation or provide a diagnosis. Tests and treatments are indicated only after medical consultation and in line with regulation.