Botulinum toxin is a protein which can cause Botulism. The toxin is produced by bacteria in badly tinned foods. The toxin prevents the release of acetylcholine into the synaptic cleft because it inhibits exocytosis. This means the muscles are forced to be relaxed and can lead to paralysis which can in turn lead to death. Botulinum toxin, however, is the active ingredient used in botox. The botulinum toxin is often used in clinical treatment, a common side effect of the treatment is limb spasticity of large muscles .