A bacterium, Clostridium botulinum, synthesizes botulinum toxin. Spores from this bacterial species are detectable in almost all natural environments, both on land and at sea. The spores have been detected in soil, fruit, vegetables, sea floors, and seafood. As these organisms grow, they synthesize botulinum, a substance with high neurotoxic potential. Indeed, botulinum is sometimes considered the compound with the greatest toxicity currently known. Toxicity arises because it prevents acetylcholine from being secreted from nerve terminals; thus, neuromuscular transmission cannot occur. The muscle involved undergoes flaccid paralysis. Botulinum toxin exists in seven different forms, which may be distinguished by serology. The forms are termed A, B, C1, D, E, F, and G. Allergan marketed the first form in the USA, type A, under the name BOTOX®. Botulinum A toxin is commercially available as onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and prabotulinumtoxinA, whereas type B is available as rimabotulinumtoxinB. There are a variety of proprietary names used for these preparations, namely BOTOX®/BOTOX® Cosmetic (OnabotulinumtoxinA), Dysport® (abobotulinumtoxinA), Xeomin® (incobotulinumtoxinA), Jeuveau® (prabotulinumtoxinA), and Myobloc® (rimabotulinumtoxinB).