Botox injections: what are they made of and what are the risks?

UK health authorities are currently investigating around 30 recent cases of botulism linked to cosmetic injections of botulinum toxin, commonly known as Botox .

These types of incidents are nothing new. Numerous cases of iatrogenic botulism, i.e., botulism caused by medical or cosmetic treatment, are reported each year.

In 2024, the U.S. Centers for Disease Control and Prevention (CDC) reported at least 19 cases of serious adverse reactions linked to counterfeit, adulterated, or improperly administered Botox injections. Those affected, mostly women, suffered symptoms such as blurred vision, dry mouth, difficulty speaking and breathing, fatigue, and general weakness. These incidents were linked to the administration of the toxin by unlicensed and untrained personnel, or in unsanitary settings such as homes or spas.

A year earlier, on March 7, 2023, the German National IHR Focal Point (NIFP) had reported to the WHO five cases of iatrogenic botulism in people undergoing medical procedures involving botulinum neurotoxin type A (BoNT/A) injections in healthcare institutions in Turkey.

Botulinum toxin is one of the deadliest substances in existence. It is produced primarily by the bacterium Clostridium botulinum—and sometimes Clostridium butyricum or Clostridium baratii. It is a ubiquitous pathogen that thrives in both soil and water.

Botulinum toxin works by blocking the release of acetylcholine, a neurotransmitter required for muscle contraction, resulting in muscle paralysis . Furthermore, by inhibiting the release of acetylcholine, it causes symptoms such as double vision (diplopia), bulbar weakness, difficulty speaking (dysphonia), speech impairment, dry mouth, and generalized muscle weakness, leading to respiratory failure.

The average lethal dose for humans has been estimated at around two nanograms of botulinum toxin per kilogram of body weight. This means that about 0.00000015 grams of this protein are enough to kill an adult of average build. If we do the math, just over a kilogram of toxin would be enough to wipe out all of humanity.

Incidentally, this same toxin appears to be behind the paretic syndrome that has been depleting seagull populations in Spain and Portugal for years.

In aesthetic medicine, botulinum toxin type A injections are known by the generic term Botox, after the brand name of the first product marketed, called BOTOX®. This type of injection has become one of the most popular cosmetic procedures worldwide .

In the United States, in 2003, just one year after the Food and Drug Administration (FDA) approved botulinum toxin for the treatment of facial glabellar lines, more than 2 million cosmetic injections were performed. Today, it is the most common cosmetic procedure for removing frown lines, forehead creases, laugh lines, and crow's feet. And the global botulinum toxin market, valued at $8.59 billion in 2025, is expected to grow at an annual rate of over 7% through 2030.

The main factors driving this growth are an aging population, the rise of minimally invasive surgeries, the rise of facial aesthetic procedures, the growing preference for non-surgical alternatives, and advances in innovation. Countries like China are experiencing significant demand, driven by rising disposable income and greater concern for personal image.

In Spain, according to the Spanish Society of Aesthetic Medicine (SEME), there were 6,725 healthcare centers authorized for aesthetic medicine in 2022, a figure that grew to 7,661 in 2024. Of the 626,778 facial aesthetic medicine treatments performed in 2021, 42% were botulinum toxin. In 2023, botulinum toxin was one of the most requested facial treatments in Spain .

Some of the best-known brand names, used for both therapeutic and cosmetic purposes, include Botox (onabotulinumtoxinA), Dysport (abobotulinumtoxinA), Xeomin (incobotulinumtoxinA), Daxxify (daxibotulinumtoxinA), and Jeuveau (prabotulinumtoxinA). There is also botulinum toxin type B, marketed as Myobloc (rimabotulinumtoxinB), which is used to treat certain medical conditions, such as severe neck spasms (cervical dystonia), when patients do not respond well to type A.

Botulinum toxin treatment is considered safe, effective, and has virtually no serious side effects. The possible side effects of botulinum toxin injection anywhere include pain, edema, erythema, ecchymosis, and short-term hypoesthesia .

In rare cases, excessive weakening of the target muscles and paresis of the adjacent muscles may occur, as well as difficulty breathing, swallowing problems, muscle weakness, and vision problems, which may require immediate medical attention.

Less serious side effects are also possible, such as ptosis or drooping eyelids , inability to fully close the eyelids, lip or eyebrow asymmetry, perception of two images of a single object, dry eye, eyelid creasing exposing the inner surface and conjunctiva, inability to close the lips firmly, involuntary drooling, and changes in facial expression, among others.

The use of botulinum toxin is contraindicated during pregnancy and lactation, in minors, and in individuals with a known hypersensitivity or allergy to botulinum toxin type A. It is also contraindicated in those taking certain muscle relaxants and antibodies such as aminoglycosides, as well as those with bleeding disorders or with infection or inflammation in the proposed injection site, and in people with neuromuscular disorders such as myasthenia gravis or amyotrophic lateral sclerosis.

In 1981, ophthalmologist Alan Scott pioneered the treatment of strabismus with botulinum toxin, paving the way for clinical research and its use in many specialties.

Today, botulinum toxin is used in the treatment of overactive bladder, urinary incontinence, chronic migraines, spasticity (contractions that cause muscle stiffness), cervical dystonia (the neck muscles contract involuntarily), excessive underarm sweating, eyelid spasms, excessive drooling, and a variety of other ophthalmological, gastrointestinal, urological, orthopedic, dermatological, dental, secretory disorders, or disorders that manifest as abnormal, excessive, or inappropriate muscle contractions.

In addition to iatrogenic botulism, which can occur if too much botulinum toxin is injected for cosmetic or medical reasons, there are other types of botulism: wound botulism, intestinal toxemia, inhalation botulism, infant botulism, and foodborne botulism. The latter is the most common, usually caused by the consumption of improperly prepared home-prepared canned food. It appears between 12 and 36 hours after ingesting contaminated food and can be very serious, requiring intensive care and antitoxin. Despite treatment, between 5% and 10% of patients die. To prevent this, it is advisable to avoid foods with strange odors, swollen cans, or preserves with bulging lids.

Infant botulism is often associated with babies consuming honey. Therefore, the American Academy of Pediatrics (AAP) recommends not giving honey to babies under 12 months old .

The history of botulism is, without a doubt, a fascinating journey from a deadly toxin to a therapeutic and aesthetic tool of immense value. The key to avoiding unnecessary risks is to only inject botulinum toxin from providers authorized and trained to administer the injection.

This article was originally published on The Conversation .