There are seven main types of botulinum toxin, named type A–G. New types are occasionally found. Types A and B are capable of causing disease in humans, and are also used commercially and medically. Types C–G are less common; types E and F can cause disease in humans, while the other types cause disease in other animals. Botulinum toxin types A and B are used in medicine to treat various muscle spasms.
Botulinum toxin is the most poisonous substance known. Intoxication can occur naturally as a result of either wound or intestinal infection or by ingesting preformed toxin in food. The estimated human lethal dose of type A toxin is 1.3–2.1 ng/kg intravenously or intramuscularly, 10–13 ng/kg when inhaled, or 1000 ng/kg when taken by mouth. Commercial forms are marketed under the brand names Botox (onabotulinumtoxinA), Dysport/Azzalure (abobotulinumtoxinA), Xeomin/Bocouture (incobotulinumtoxinA), and Jeuveau (prabotulinumtoxinA).