Botulinum toxin (BTX) is a neurotoxic protein produced by the bacterium Clostridium botulinum and related species. Botulinum toxin causes the disease botulism, however it is also used commercially in medicine, cosmetics, and research. There are seven types of botulinum toxin, named type A-G. Type 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 and diseases characterized by overactive muscle.