Frown lines, forehead and crow's feet: botulinum toxin area by area

One muscle, one line

Botulinum toxin type A is a prescription-only medicine, often called "botox". It is a purified protein that blocks, for a few months, the signal between nerve and muscle. The injected muscle contracts less, and the skin over it creases less. It therefore acts on expression lines, the ones drawn by your movements.

Its effect on these lines is well documented. A Cochrane review published in 2021, bringing together 65 trials and nearly 15,000 participants, confirms that it reduces them within four weeks. It also notes that it probably increases the risk of a drooping eyelid. This effect is uncommon and temporary, and depends largely on how the injection is done.

Frown lines: the area between the brows

Frown lines are the vertical creases between the eyebrows. They are drawn by a small group of muscles that pull the brows down and towards the middle when you frown. The product information usually provides for five injection points in these muscles.

The precaution here concerns the eyelid. If the product spreads too low, down to the muscle that lifts the upper eyelid, the lid may droop slightly for a while. This is why injections stay away from the eye, at least one centimetre above the bony rim of the eye socket. This risk is estimated at 1 to 5%.

The forehead: relaxing without lowering the brow

Horizontal forehead lines appear when you raise your eyebrows: they are drawn by the frontalis muscle. It is also the muscle that lifts the brows. Relaxing it too much can lower the brow or cause a feeling of heaviness in the forehead.

One product leaflet asks for injections at least two centimetres above the eyebrow. An international consensus points the same way: lower doses in the upper face and, for some experts, very superficial injections near the brow, to soften the lines without lowering the brow. I also take into account the frown muscles, which pull the brow down: the forehead is always assessed together with the rest of the eye area.

Crow's feet: the corner of the eye

Crow's feet are the fine lines that fan out at the outer corner of the eye when you smile. They come from the outer part of the muscle that closes the eye. One product leaflet provides for three points on each side, the first about one centimetre outside the rim of the eye socket.

Two precautions: stay away from the eye, and do not go too low towards the cheekbone, where a muscle that lifts the lip when you smile runs close by. An injection too near this muscle can make the corner of the lip droop slightly. The aim is to soften the creasing, not to change your smile.

Why measured doses

• To keep your expressions. International recommendations speak of modulating the muscle rather than paralysing it.
• To limit side effects caused by the product itself, such as a drooping eyelid or eyebrow. They come from too strong an effect or from spread to a neighbouring muscle.
• To preserve effectiveness over time. Doses that are too high or too frequent can encourage antibodies that make the toxin less effective.

This is also why, the first time, we always do less: we can always add at the check-up, taking away is harder.

What it does and does not do

The toxin mainly softens lines that only appear with movement. On a line already visible at rest, the effect is more modest, and when the line comes mainly from loss of skin elasticity, it may not be enough. It does not restore volume and does not change skin texture: those are other treatments, which we can discuss at the consultation.

Duration, timing and the check-up around day 15

The first effects appear between the third and the fourteenth day, and the result takes about two weeks to settle. So I see you again around day 15, with the same photographs, to adjust if needed. The day-by-day course is the subject of another article.

The effect usually lasts three to five months: around four months in studies, a little longer in some people. The product information requires at least three months between two sessions. There is therefore no fixed schedule: a new session is done when the movement returns and bothers you again. Data on sessions repeated over many years, however, remain limited.