Botulinum toxin is a neurotoxin protein produced by the bacterium Clostridium botulinum. It is one of the most poisonous naturally occurring substances in the world, and it is the most toxic protein. Though it is highly toxic, it is used in minute doses both to treat painful muscle spasms, and as a cosmetic treatment in some parts of the world. It is sold commercially under the brand names Myobloc, Botox and Dysport for this purpose. The terms Myobloc, Botox and Dysport are trade names and are not used generically to describe the neurotoxins produced by the clostridia species.