Medical uses

Researchers discovered in the 1950s that injecting overactive muscles with minute quantities of botulinum toxin type A decreased muscle activity by blocking the release of acetylcholine at the neuromuscular junction, thereby rendering the muscle unable to contract for a period of 4 to 6 months.
Alan Scott, a San Francisco ophthalmologist, first applied tiny doses of the toxin in a medicinal sense to treat crossed eyes and uncontrollable blinking, but needed a partner to gain regulatory approval to market his discovery as a drug. Allergan, Inc., a pharmaceutical company that focused on prescription eye therapies and contact lens products, bought the rights to the drug in 1988 and received FDA approval in 1989. Allergan renamed the drug Botox.
Cosmetically desirable effects of Botox were quickly discovered thereafter when the frown lines between the eyebrows were observed to soften following treatment for eye muscle disorders, leading to clinical trials and subsequent FDA approval for cosmetic use in April 2002. As of 2006, Botox injection is the most common cosmetic operation in the United States.
Besides its cosmetic application, Botox is used in the treatment of
migraine headaches
cervical dystonia (a neuromuscular disorder involving the head and neck)
blepharospasm (involuntary contraction of the eye muscles)
severe primary axillary hyperhidrosis (excessive sweating)
achalasia (failure of the lower esophageal sphincter to relax)
Other uses of botulinum toxin type A that are widely known but not specifically approved by FDA include treatment of:
involuntary microexpression facial triggers (concealing a lie)pediatric incontinence, incontinence due to overactive bladder, and incontinence due to neurogenic bladder.
anal fissure
spastic disorders associated with injury or disease of the central nervous system including trauma, stroke, multiple sclerosis, Parkinson's disease, or cerebral palsy
focal dystonias affecting the limbs, face, jaw, or vocal cords
TMJ pain disorders
diabetic neuropathy
wound healing
excessive salivation
In the Journal of Dermatologic Surgery, Eric Finzi claims to have treated clinically depressed patients with botox. On Good Morning America, he claimed that by taking away the ability to frown, he was somehow taking away the ability to feel depressed.
Treatment and prevention of chronic headache and chronic musculoskeletal pain are emerging uses for botulinum toxin type A. In addition, there is evidence that Botox may aid in weight loss by increasing the gastric emptying time.