A toxin (from Ancient Greek: τοξικόν toxikon) is a poisonous
substance produced within living cells or organisms; man-made
substances created by artificial processes are thus excluded.
The term was first used by organic chemist Ludwig Brieger
(1849–1919). Toxins can be small molecules, peptides, or
proteins that are capable of causing disease on contact with or
absorption by body tissues interacting with biological
macromolecules such as enzymes or cellular receptors. Toxins
vary greatly in their severity, ranging from usually minor and
acute (as in a bee sting) to almost immediately deadly (as in
botulinum toxin). Toxins are often distinguished from other
chemical agents by their method of production - the word toxin
does not specify method of delivery (compare with venom and the
narrower meaning of poison – all substances that can also cause
disturbances to organisms). It simply means it is a biologically
produced poison. There was an ongoing terminological dispute
between NATO and the Warsaw Pact over whet