How Do Anti-Wrinkle Injections Work?

Anti-wrinkle injections are one of the most common treatments I perform, and yet I still get asked the basics almost every week. Do they remove wrinkles? Freeze the face? Do something to the skin itself? What's happening between the injection and the moment someone notices their frown lines have softened?

The short answer is simple: the injections reduce the signal travelling from certain nerves to certain facial muscles, which weakens the contraction of those muscles and softens the lines that contraction was creating. But the longer answer is more interesting, and it's worth understanding properly before you have anything done to your own face. So, that's what I want to walk through here.

What are anti-wrinkle injections doing?

A lot of the lines we develop are down to repeated expression. Every time you frown, squint, or raise your eyebrows, a muscle underneath the skin contracts and pulls the skin above it along with it. When you're younger, that skin just springs back once the expression passes. As the years go on, the combination of that repeated movement with declining collagen and elastin means the crease starts sticking around even after the expression is over — eventually it's visible even at rest.

What the injections do is turn down the volume on the muscles behind some of those expressions. I want to be clear that the goal isn't to switch a muscle off completely. Good treatment is about dialing back the excess, not erasing the movement altogether.

The mechanism, properly explained

Muscles don't decide to contract on their own — they're told to by a nerve. At the point where a nerve meets a muscle, it releases a chemical called acetylcholine, which crosses that tiny gap and instructs the muscle fibres to fire.

Small, carefully placed amounts of the prescribed medicine interrupt that handover. Less acetylcholine gets released, the "contract" message arrives weaker, and the muscle simply does less. Because the skin above it is no longer being folded as forcefully or as often, the associated lines soften. And crucially, this whole process reverses on its own — nerve signalling comes back over the following months, and muscle activity returns with it.

Does it work on the skin itself?

No, and I think this is where a lot of the confusion comes from. People sometimes talk about the injections as though they're filling in a line the way filler might. They're not. The target is the nerve-muscle communication, not the wrinkle itself, which is exactly why this treatment is so effective on dynamic lines — the ones caused or worsened by movement, like the horizontal lines across the forehead, the vertical ones between the brows, or crow's feet when you smile.

Dynamic lines vs. static lines

This distinction matters more than people realise when they're weighing up treatment.

Dynamic lines only really show up when you're mid-expression. Raise your eyebrows in the mirror right now — those forehead lines that appear are dynamic. Relax your face, and if they mostly vanish, that confirms it. These respond very well to treatment, because muscle activity is doing most of the work in creating them.

Static lines are the ones still visible when your face is completely at rest. They come from a mix of things — years of repeated movement, yes, but also collagen decline, sun exposure, genetics, smoking, and structural changes as we age. Treatment can still help here, mainly by stopping the muscle from continuing to fold the skin along the same crease, but I won't promise a deep, established static line will disappear entirely just because the muscle underneath has quietened down. I'd rather set that expectation honestly upfront than have someone disappointed at their two-week review.

Where it's commonly used

The upper face is where most of my anti-wrinkle work happens — frown lines, forehead lines, and crow's feet.

Frown lines sit between the brows and come from muscles that pull the eyebrows down and inward. Softening those muscles eases the frown while leaving normal expression intact.

Forehead lines come mainly from the frontalis muscle, the one responsible for lifting your eyebrows. This is an area that needs real care, because eyebrow position depends on a balance between several muscles working together — go too aggressive here and you risk a heavy, flat look rather than a natural one.

Crow's feet form at the outer corners of the eyes, especially when smiling. Well-placed treatment softens them without taking away your smile.

There are other areas I treat too, but they all demand a solid grasp of the anatomy and how neighbouring muscles interact with each other.

Why you won't see results straight away

This surprises a lot of people. The injections themselves take minutes, but the biological process behind the result is gradual. Most people start noticing something around day three or four, and it keeps developing from there. I always tell patients to properly judge the result at the two-week mark — checking your forehead the next morning is judging it far too soon.

What the appointment is like

The injections themselves are quick — a fine needle, a small volume, and most people describe it as barely more than a pinprick. But a proper appointment should involve a lot more than the injecting part. Before I touch a needle to anyone's face, I'm assessing how they move — muscle strength, eyebrow position, symmetry, how different muscles are working together. Everyone's pattern is slightly different, and that assessment is really what decides where the injections go. The injecting is the fast part; the thinking beforehand is what takes the time.

Will it freeze my face?

It shouldn't. A completely immobile forehead isn't the outcome I aim for. There's a real difference between reducing excess movement and eliminating movement altogether, and personally I lean toward the former. I want someone to look fresher, less tired, less tense, not embalmed!

How much movement someone keeps depends entirely on them. Some patients want very little left. Others specifically want to hold onto expression. I tend to err on the side of at least some movement though.

Why doses differ so much between people

Faces simply aren't standard-issue. Two people the same age can have very different muscle strength, proportions, and expression habits — someone with strong frown muscles needs a different approach to someone with naturally weaker ones. Men, on average, tend to carry more facial muscle mass and often need different dosing as a result, often fifty percent more, hence it is a little more expensive for men.

Other things I factor in include muscle strength, eyebrow position, forehead height, any existing asymmetry, what's been done before, how much movement someone wants to keep, and general skin quality. This is exactly why I don't work off a standard template — the treatment should be built around the face, not the other way round.

How long does it last?

For most people, roughly four months, though there's real variation from patient to patient. It doesn't wear off overnight — movement gradually creeps back in, so you might notice a little more expression returning while the overall result still looks good, and it continues from there. Muscle strength, the area treated, and your own biology all play into how long it holds. I've written more on this specifically in a separate piece, if you want the fuller picture.

Does it weaken the muscle permanently?

No — the effect is built to be temporary. As the nerve-muscle communication recovers, so does the muscle. If you decide to stop treatment altogether, your movement comes back and your face simply continues ageing as it would have anyway; it doesn't rebound worse for having had treatment. That said, with repeated treatment over time, some patients find their strongest muscles calm down somewhat or that they need touch-ups less often — though this varies a lot person to person.

Can it prevent wrinkles from forming?

To an extent, yes, by reducing one of the mechanisms that creates them. Think of folding a piece of paper along the same line again — eventually there's a crease there even flat. Skin isn't paper, but the same basic principle of repeated folding applies. Less forceful, less frequent folding means less pressure driving a new line to form.

That said, facial ageing is a lot more than muscle movement. Sun exposure, genetics, smoking, collagen loss, hormones, and changes in facial fat and bone all play a part too, so I'd never present this as a fix for ageing generally — just one piece of it.

Is it safe?

It's a well-established treatment with a long track record in both medical and aesthetic use. Temporary effects can include redness, swelling, tenderness, bruising, headache, or some asymmetry. Less commonly, a nearby muscle can be affected unintentionally, which might cause temporary eyebrow or eyelid drooping. This is exactly why careful assessment and proper dosing matter, and why a good consultation should also flag when treatment isn't the right call, or should wait.

What makes a result look natural?

To me, success was never about eliminating every line possible. A face needs to move — expression is part of how we communicate and part of what makes someone recognisably themselves. My job is figuring out which muscles are driving the lines someone doesn't want, and how much to dial each one back, which sometimes means treating two areas quite differently or deliberately leaving movement in place elsewhere.

The best outcome, in my opinion, is one nobody else clocks as "work." You just look a bit fresher, a bit less tense, a bit more like you got some sleep.

Common questions

How quickly does it start working? Some people see changes within three to four days, developing further from there. I'd assess the true result around the two-week mark.

How long does it last? Around three to four months for most people, though it varies.

Will I still be able to move my face? Yes — how much depends on the plan and dose, and it can be tailored to keep your expression natural.

Does it get rid of existing wrinkles? It works particularly well on dynamic lines caused by movement. Deeper static lines may soften but won't necessarily disappear entirely.

What happens once it wears off? Nerve-muscle communication gradually returns and muscle activity comes back with it — a slow fade, not a sudden drop-off.

Will my lines be worse once I stop? No. Movement returns and your face carries on ageing normally — treatment doesn't set you back.

How often do people come back for treatment? Many patients settle into roughly every three to four months, though there's no single schedule that suits everyone.

Final thoughts

At its core, this treatment works by quietening the signal between certain nerves and certain facial muscles. Less contraction means less repeated folding of the skin, and that's what softens expression lines. The science itself isn't complicated. The real skill is in the judgment — which muscles to treat, exactly where, and by how much.

I've never seen the goal as an expressionless face. It's about using a proper understanding of the anatomy in front of me to get a result that looks balanced, subtle, and right for that person. If you're weighing up anti-wrinkle injections in Dublin, a proper consultation is about two things: working out what you'd like to change, and just as importantly, agreeing on what's better left alone.

Dr David Lucey is the multi-award winning founder of The Beauty Doc, a doctor-only medical aesthetics clinic in Dublin. His approach centres on careful facial assessment, subtle treatment, and natural-looking results.

Click Me