Botulinum toxin A (BoNT/A) is a protein produced by the bacterium Clostridium botulinum, which causes botulism, a rare but potentially fatal disease that affects the nervous system. BoNT/A blocks the release of acetylcholine, a neurotransmitter that enables muscle contraction, resulting in flaccid paralysis. BoNT/A is one of the most lethal substances known, with an estimated human lethal dose of 1.3–2.1 ng/kg intravenously or intramuscularly. However, BoNT/A also has various medical and cosmetic uses, as it can selectively weaken specific muscles or reduce excessive sweating, salivation, or secretion.

BoNT/A is used to treat a number of disorders characterized by overactive muscle movement, such as cerebral palsy, post-stroke spasticity, post-spinal cord injury spasticity, spasms of the head and neck, eyelid, vagina, limbs, jaw, and vocal cords. BoNT/A injections can reduce muscle stiffness, pain, and contractures, and improve function and quality of life. BoNT/A is also used to treat chronic migraine, overactive bladder, excessive sweating (hyperhidrosis), drooling (sialorrhea), and crossed eyes (strabismus). BoNT/A works by blocking the nerve signals that stimulate the affected muscles or glands, thereby reducing their activity.

BoNT/A is widely used for cosmetic purposes to reduce facial wrinkles and improve appearance. BoNT/A injections can temporarily smooth out frown lines, forehead creases, crow’s feet, and other expression lines by relaxing the underlying muscles that cause them. BoNT/A can also be used to lift the eyebrows, correct a gummy smile, slim the jawline, and soften neck bands. BoNT/A injections are generally safe and effective when performed by a qualified professional, but they may cause some side effects such as bruising, swelling, headache, drooping eyelids, or allergic reactions.

BoNT/A is a neurotoxic protein that can cause botulism, a life-threatening disease that paralyzes the muscles and affects the breathing. However, BoNT/A also has many beneficial applications in medicine and cosmetics, as it can selectively weaken specific muscles or glands to treat various conditions or enhance appearance. BoNT/A injections are administered in small doses and require repeated treatments to maintain the desired effects.

BoNT/A has a long and fascinating history that spans over a thousand years. The first recorded cases of botulism were reported in the tenth century by German poets who described the symptoms of food poisoning after eating spoiled sausages. The term “botulism” comes from the Latin word for sausage, “botulus”. In 1897, a Belgian scientist named Emile van Ermengem isolated the bacterium Clostridium botulinum from a ham that caused an outbreak of botulism in a musical band. He also discovered that the bacterium produced a toxin that was responsible for the paralysis. In 1928, another Belgian scientist named Herman Sommer purified and crystallized BoNT/A for the first time and demonstrated its lethal effect on mice. During the 1940s, BoNT/A was studied as a potential biological weapon by several countries, including the USA, Japan, Germany, and the UK. However, no successful weaponization of BoNT/A was achieved.

In 1949, two American scientists named Burgen and Brooks discovered that BoNT/A blocked the release of acetylcholine at the neuromuscular junction, thus explaining its mechanism of action. In 1968, Alan Scott, an ophthalmologist, began to use BoNT/A to treat strabismus (crossed eyes) in monkeys. He later obtained a sample of BoNT/A from Edward Schantz, a biochemist who had developed a method to produce large quantities of purified BoNT/A. In 1977, Scott and Schantz published their first clinical results on the use of BoNT/A for human strabismus. In 1980, Jean Carruthers, an ophthalmologist, and Alastair Carruthers, a dermatologist, noticed that their patients who received BoNT/A injections for blepharospasm (eyelid spasms) also had reduced wrinkles around their eyes. They realized that BoNT/A could be used for cosmetic purposes and pioneered its use for facial rejuvenation. In 1989, BoNT/A was approved by the US Food and Drug Administration (FDA) for the treatment of blepharospasm and strabismus under the brand name Botox.

Since then, BoNT/A has been approved for many other medical and cosmetic indications, such as cervical dystonia (neck spasms), chronic migraine, overactive bladder, hyperhidrosis (excessive sweating), sialorrhea (drooling), and glabellar lines (frown lines). BoNT/A has also been modified and improved by various manufacturers to produce different formulations with different properties and potencies. Some of these formulations include Dysport (abobotulinumtoxinA), Xeomin (incobotulinumtoxinA), Jeuveau (prabotulinumtoxinA), and Letybo (letibotulinumtoxinA). BoNT/A is currently one of the most widely used and researched drugs in medicine and cosmetics, with more than 1000 clinical trials and over 3000 scientific publications.