A toxin is quite often a naturally occurring byproduct of many bacterial species, which, when it interacts with living tissue, will often cause harm through interference with basic cell mechanisms, leading to cell death, and eventually, if the bacterial growth is not checked, massive tissue damage, or even death.
Botulism is one such disease caused by bacterial toxins produced by Clostridium botulinum. Recently, a method of controlled injections with the toxic has been used to aid in cosmetic surgery, allowing human beings to profit from the paralyzing nature of the toxins.