Botulinum toxin – what is it and how does it work?

Botox (onabotulinumtoxin A) is the best-known brand name for botulinum toxin. Other brand names for the drug include Dysport (abobotulinumtoxin A) and Xeomin (inkobotulinumtoxin A).

Botulinum toxin is one of the best-known active ingredients used in aesthetic treatments. Although the word Botox is often associated solely with wrinkle treatment, it is originally a medical product whose properties were initially harnessed for the treatment of diseases.

In this article, I explain what botulinum toxin is, how it works at the tissue level, and what it is used for.

Why is medical expertise important?

The outcome of Botox treatments depends on a thorough understanding of anatomy and precise dosing. Even within the same muscle group, muscle activity can vary from person to person. This affects both the treatment plan and the final result.
– Ville Männistö

What is botulinum toxin?

Simply put: Botulinum toxin is a neurotoxin used in medicine in very small doses to reduce muscle activity.

Medically speaking: Botulinum toxin is a neurotoxin produced by the bacterium Clostridium botulinum. It is one of the best-known neurotoxins. In medicine, it is used in very small, precisely measured doses, in which case it acts not as a toxin but as a medication.

There are several different types of botulinum toxins (A–G), of which type A is the most commonly used in medical practice.

Although botulinum toxin is, in essence, a toxin, when used properly, it is a safe and extensively studied medication.

It's the dose that makes the poison.

How does botulinum toxin work?

Simply put: Botulinum toxin prevents muscles from contracting normally.

When a muscle is unable to contract with its usual intensity, the skin overlying the muscle cannot wrinkle normally either. Through this mechanism, botulinum toxin smooths out wrinkles and refreshes the overall appearance of the face.

Medically speaking: Botulinum toxin acts on the junction between the nerve and the muscle (neuromuscular junction).

Normally, a nerve releases a neurotransmitter called acetylcholine, which causes the muscle to contract. Botulinum toxin blocks the release of this neurotransmitter.

As a result

• the nerve signal is not transmitted to the muscle
• the muscle relaxes
• the formation of wrinkles is reduced

The effect is not permanent. Nerve endings recover over time, and muscle function usually returns within about 3 to 6 months.

Botulinum toxin does not destroy muscle or nerve tissue. It temporarily blocks communication between them. Once the effect wears off, communication returns to normal. The treated muscle fully recovers 9–12 months after the procedure. Long before the aforementioned 9–12-month mark, the visible effects of the treatment have faded.
– Ville Männistö

How long does botulinum toxin last, and why does its effect wear off?

Simply put: the effects of Botox usually last about 3 to 6 months.

After this, the muscle gradually begins to function normally again, and, for example, the treated lines reappear.

Medically speaking: Botulinum toxin prevents the nerve ending from releasing acetylcholine by breaking down the SNAP-25 protein. This interrupts communication between the nerve and the muscle, preventing the muscle from contracting normally.

However, the effect is not permanent, because over time, nerve endings begin to form new connections to the muscle. This is called neural reorganization.

Why isn't the effect permanent?

Botulinum toxin does not cause permanent damage to muscles or nerves. It only temporarily blocks communication between the nerve and the muscle.

Over time, the body begins to repair this connection:

• nerve endings form new connections to the muscle
• the release of the neurotransmitter (acetylcholine) is restored
• muscle contraction begins again

This explains why the effect gradually fades rather than ending abruptly.

Factors affecting the duration of the effect include, for example

• strength of the muscle being treated
• dosage
• individual metabolism

Botulinum toxin does not “wear off” like, say, hyaluronic acid gel. The effects of botulinum toxin wear off once the nerve-muscle connection returns to normal.

Is botulinum toxin dangerous?

The safety of botulinum toxin is dose-dependent: the same substance can be toxic in large quantities but safe in small, precisely targeted medical doses.

If someone wanted to kill a person with botulinum toxin, they would need a dose worth an estimated hundreds of thousands of euros.
– Ville Männistö

Simply put: when administered in the correct dosage, botulinum toxin is a safe medication, and when performed correctly, botulinum toxin treatment is a safe medical procedure.

Botulinum toxin has been used in medicine for decades, and its use in aesthetic treatments is also well established.

Medically: Botulinum toxin acts locally at the neuromuscular junction by blocking the release of acetylcholine. When properly dosed and targeted, its effect is limited to the treated muscle or tissue.

Safety is based on the fact that

• The dose is small and precisely targeted
• the effect is localized; it does not affect the entire body
• the effect will subside over time

Possible side effects are most often related to the injection or the spread of the drug’s effects to surrounding muscles:

• mild redness or swelling at the injection site
• a small bruise
• temporary muscle weakness in the treated area

In rare cases, botulinum toxin may also affect muscles other than the intended target:

• drooping eyelids
• difficulty swallowing
• speech difficulties
• breathing difficulties

These side effects are rare, but require medical attention.

Safety depends on proper patient selection, correct dosing, and a solid understanding of anatomy.

You can find practical instructions for aftercare in the article " After Botox Injections."

What is botulinum toxin used for?

Simply put: botulinum toxin is used to relax overactive muscles.

This hyperactivity may manifest itself aesthetically as lines or, functionally, as muscle tension, teeth grinding, or tension headaches.

Medically speaking: Botulinum toxin reduces muscle activity by blocking the function of the neuromuscular junction. For this reason, it can be used for both aesthetic and medical purposes.

The aesthetic use of botulinum toxin

In cosmetic applications, botulinum toxin targets the facial muscles responsible for causing wrinkles.

Simply put: The treatment reduces muscle movement, so the skin doesn't crease as much as it used to. As a result, the fine lines in the treated area are smoothed out.

Medically speaking: botulinum toxin blocks the release of acetylcholine at the neuromuscular junction by cleaving the SNAP-25 protein, which is essential for the transmission of nerve impulses to the muscle.

When a muscle does not receive the normal signal to contract, its activity temporarily decreases. This prevents the skin from repeatedly wrinkling and allows the lines to smooth out.

Botulinum toxin is particularly effective on so-called dynamic wrinkles, which are caused by muscle movement:

• horizontal lines on the forehead
• the Sibelius wrinkle between the corners
• crow's feet

The effects begin within a few days, peak in about two weeks, and last an average of 3–4 months.

The effect is reversible because nerve endings form new connections with the muscle over time.

👉 Learn more about cosmetic botulinum toxin treatments:

• A Comprehensive Guide to Botox Treatments
• Botox & Forehead
• Botox & frown lines
• Botox & Lips

Medical use

Botulinum toxin is used to treat a variety of functional problems:

• bruxism (teeth grinding)
• chronic migraine
• excessive sweating (hyperhidrosis)

In these situations, the goal is not aesthetic change but rather symptom relief and an improved quality of life.

Simply put: Botox treatment relaxes the overactive muscle or gland that is causing the symptoms.

Medically speaking: Botulinum toxin blocks the transmission of nerve impulses to the target tissue by cleaving the SNAP-25 protein, which is an essential mediator for the release of acetylcholine. When the nerve is unable to transmit the signal normally, excessive activity in the muscle or gland is reduced.

Bruxism and botulinum toxin

In bruxism, or teeth grinding, botulinum toxin is used to reduce excessive activity in the jaw muscles.

Simply put: the treatment weakens the muscles involved in chewing, which reduces and eventually stops the grinding.

When treating teeth grinding, botulinum toxin is typically injected into the masseter muscles at the corners of the mouth and the temporalis muscles, which are responsible for clenching the jaw tightly.

Medically speaking: botulinum toxin blocks the release of acetylcholine at the neuromuscular junction by cleaving the SNAP-25 protein. This prevents the muscle from contracting normally.

When muscle contraction strength decreases

• biting force decreases
• muscle strain is reduced
• pain and tension may be relieved

At the same time, this breaks the so-called pain cycle, in which continuous muscle contraction impairs blood flow and increases the release of pain-transmitting substances.

Botulinum toxin treatment can also reduce the size of the masseter muscle over time if the muscle has become enlarged due to constant strain.

• The effects usually begin within 2 to 5 days
• Maximum results are achieved in 2–4 weeks
• The effect typically lasts 3–6 months

Treatment does not eliminate the underlying cause of bruxism, but it can reduce muscle tension and thus alleviate the symptoms of teeth grinding.

Migraine and botulinum toxin

In the treatment of migraines, the effect of botulinum toxin is not based solely on muscle relaxation.

Simply put: the treatment prevents the release of pain-transmitting neurotransmitters from nerve endings, which can reduce the frequency and severity of migraine attacks.

Medically speaking: Botulinum toxin reduces the hypersensitivity of sensory neurons. Substances that transmit pain include, for example, CGRP (calcitonin gene-related peptide), glutamate, and substance P.

This effect is based on the fact that botulinum toxin cleaves the SNAP-25 protein, which is part of the SNARE complex required for nerve cell signaling. This prevents nerve endings from releasing pain-transmitting substances.

As the transmission of pain signals is reduced, the sensitization of the nervous system also decreases. This can prevent migraine attacks from occurring and reduce their severity.

Botulinum toxin

• affects pain-transmitting nerve endings in particular
• reduce stimuli to the peripheral nervous system
• blocks the transmission of pain signals to the central nervous system

The effect of botulinum toxin on migraines is therefore not limited to the muscles but also—and above all—involves the regulation of nervous system function.

Excessive sweating and botulinum toxin

In the treatment of excessive sweating, botulinum toxin directly affects the function of the sweat glands.

Simply put: the treatment blocks the nervous system’s signal to the sweat glands, which is why sweating decreases in the treated areas.

Medically speaking: Botulinum toxin blocks the release of the neurotransmitter acetylcholine from the nerve ending. It does this by cleaving the SNAP-25 protein, which is essential for the transmission of nerve impulses to the sweat glands.

When a sweat gland does not receive a signal from the nervous system, it does not activate normally. This is why excessive sweating stops.

When treating excessive sweating with botulinum toxin

• The effects usually begin within a few days
• The maximum effect is achieved in about 2–3 weeks
• The effect typically lasts 4–7 months

The treatment is precisely targeted at the areas where sweating is most severe. These areas include the underarms, palms, and soles of the feet.

Botulinum toxin treatment for the bladder

In the treatment of overactive bladder, botulinum toxin is used to reduce excessive contractions of the bladder muscle.

Simply put: the treatment relaxes the bladder, reducing the urge to urinate and allowing the bladder to hold more urine.

Medically: Botulinum toxin blocks the release of acetylcholine from nerve endings by cleaving the SNAP-25 protein. This reduces involuntary contractions of the detrusor muscle (the bladder muscle).

In addition, botulinum toxin can affect the sensory nerves of the bladder and reduce the signals that trigger the urge to urinate.

• The urge to urinate decreases
• The frequency of urination decreases
• The capacity of the bladder increases

The effect is temporary and typically lasts about 6 to 9 months.

The treatment is usually administered into the bladder wall using a cystoscope.

How quickly does botulinum toxin take effect?

• 3–5 days: first effects
• 10–14 days: final result

The effect does not begin immediately, because the inhibition of neuromuscular transmission occurs gradually.

How long does botulinum toxin last?

The effects of botulinum toxin usually last 3 to 6 months.

The duration of the effect depends, among other things, on:

• treatment area
• muscle strength
• of the dose used

You can view examples of the results here:

👉 Before and after Botox

What are the possible side effects of botulinum toxin?

The most common side effects are

• redness at the injection site
• mild swelling
• a small bruise

Less common are

• muscle weakness in the adjacent area
• drooping eyelids

Serious symptoms, such as difficulty swallowing or breathing, require immediate medical attention.

Is botulinum toxin a poison?

Yes, botulinum toxin is a neurotoxin.

The key factor is the dosage. The amounts used in medicine are extremely small and safe when the treatment is administered correctly. When treating cosmetic issues, the amounts are even smaller.

Frequently Asked Questions About Botulinum Toxin

Can botulinum toxin spread throughout the body?

Botulinum toxin primarily acts locally at the injection site. In rare cases, the effect may spread to adjacent muscles. This spread can be prevented by proper injection technique, correct dosing, and selection of the most appropriate botulinum toxin product.

Is botulinum toxin permanent?

No. The effect lasts 3–6 months. After that, muscle function returns to normal.

Does getting Botox injections hurt?

The injections are given with a very fine needle. Most people describe the needle pricks as feeling like small pinpricks.

Can botulinum toxin change facial expressions?

Excessive or improperly targeted treatment can affect one's appearance, but when properly planned and executed, the result is natural.

Summary: What is botulinum toxin?

Botulinum toxin is a medication that temporarily reduces muscle activity.

It is used for both aesthetic and medical purposes:

• for the aesthetic fading of stretch marks
• for the medical treatment of muscle tension and other functional symptoms

The effect is based on the inhibition of neuromuscular transmission, preventing the muscle from contracting normally.

The effects begin within a few days, peak in about two weeks, and usually last 3–6 months.

When performed correctly, the treatment is safe. Its effects diminish and eventually disappear over time.

Botulinum toxin is not a filler, and its effects are not permanent. The injections are precisely targeted, and the goal of the treatment is always to temporarily regulate muscle function.