Botulinum toxin: the complete guide

Botulinum toxin type A is a medicine regulated by INFARMED, with approved aesthetic indications and over thirty years of use in medicine. This guide covers what it does in the tissue, which areas have an established indication, what to expect on the day and in the days that follow, how long it lasts and when the result has limits. It is what the Cosmo Clinic clinical team covers at an assessment consultation before any treatment decision.

How it works in the muscle

Botulinum toxin reversibly blocks the release of acetylcholine at the nerve endings that control muscle contraction. Without that signal, the muscle relaxes. The skin over it creases less and dynamic wrinkles, the ones that appear with expression, soften.

The effect is local and dose-dependent. The dose determines the degree of relaxation: a calibrated dose preserves some natural movement; an excessive dose removes it. Calibration is done zone by zone, based on the strength and thickness of each muscle, assessed before any injection.

The body regenerates the nerve endings over months. The effect is not permanent: it fades between 3 and 6 months, with individual variation. The muscle recovers full function.

Dynamic wrinkles and static wrinkles: why the difference matters

Botulinum toxin treats dynamic wrinkles: the ones that appear with muscle movement and disappear, or sit soft, at rest. Static wrinkles, etched at rest and visible even with the face relaxed, respond better to hyaluronic acid filler or to a combination of both approaches. Which treatment is appropriate is decided at the assessment consultation.

Areas treated

Facial areas with established aesthetic indication include:

• Forehead: horizontal lines that appear when raising the brows. Careful dosing avoids the heavy-brow effect.
• Glabella (frown lines): the vertical lines between the brows, among the most treated areas.
• Crow's feet: the radial lines at the outer corners of the eyes when smiling or squinting.
• Nose: diagonal lines on the nose bridge when smiling (bunny lines).
• Upper lip: relaxing the muscle for a slight outward curl of the lip (lip flip).
• Chin: softens the uneven texture on the chin.
• Neck: prominent platysmal bands when tensing the neck.

The decision to treat a particular area, and the appropriate dose, depends on the individual's muscle anatomy. Not every area has an indication for every person.

What to expect: before, during and after

Before the injection. The clinical team assesses expression at rest and in movement, records the individual muscle pattern and defines the zones and doses. No toxin is applied before that mapping.

At the session. The procedure takes 15 to 30 minutes depending on the number of zones. Numbing cream can be applied beforehand if preferred. The injections are precise, using a fine needle. Right after, small red dots and mild swelling at the injection points are normal and resolve within minutes to hours.

In the days that follow. The effect begins between 3 and 7 days. The full result is assessed at day 14, when the toxin has reached maximum action. The day-14 review consultation is included.

How long it lasts

On average, between 3 and 6 months. Factors that influence duration:

• Area treated: more active muscles tend to recover faster.
• Dose: more conservative doses have a shorter effect.
• Individual metabolism: varies from person to person; the first treatments are where calibration happens.
• Heat exposure: prolonged high temperatures, such as frequent sauna use, accelerate breakdown.

With regular treatments, some people find that the dose needed decreases over time, as the muscles adapt their contraction pattern.

Risks and side effects

With an approved product and correct technique, the safety profile is well documented. The most common effects are local and temporary:

• Bruising at the injection point, resolving in 3 to 10 days.
• Mild swelling in the first hours.
• A passing headache on the day, in 5 to 10% of cases.
• A feeling of heaviness or tightness in the treated zones for the first 24 to 48 hours — this is normal and is a sign the toxin is taking effect.

Less common: eyelid ptosis, when the toxin migrates beyond the target muscle. It occurs in under 1% of cases, is temporary, and resolves in weeks as the toxin breaks down.

When to contact the clinic: pain that increases from the second day, marked asymmetry in the first 48 hours, or any sign of infection.

Who should not have it

Absolute contraindications: pregnancy, breastfeeding, neuromuscular conditions (myasthenia gravis, ALS, Lambert-Eaton syndrome) and a documented allergy to any component. An active infection at the injection site is a temporary contraindication.

Anticoagulants and some antibiotics are declared at the assessment consultation and discussed case by case.

Aftercare

In the first 24 hours: no intense exercise, no heat (sauna, very hot bath), no alcohol, no massage on the treated zones, no lying down for 4 hours after the injection. Light make-up from 4 to 6 hours on.

In the first 48 hours: no direct pressure on the treated zones, no sauna.

Full aftercare details are in botulinum toxin aftercare.

When to start

There is no right age. The question is whether dynamic wrinkles are already setting in at rest, or whether a muscle pattern is active enough to start leaving marks. The full criteria and age context are in when to start botulinum toxin.

Cost

The cost depends on the areas and the dose. Prices by area are on each treatment page: forehead, frown lines, crow's feet. You can also see all toxin treatments on the wrinkle treatments page. The assessment consultation is free.