A blood agent or cyanogen agent is a chemical compound, carried by the blood for distribution through the body. Blood agents may contain the cyanide group, which can inactivate the energy-producing cytochrome oxidase enzymes of cells in the body. The term "blood agent" is a misnomer, however, because these agents do not typically affect the blood, though they may interrupt the production of blood components, i.e. benzene. Rather, they exert their toxic effect at the cellular level, by interrupting the electron transport chain in the inner membranes of mitochondria (see cyanide). Blood agents may all act upon tissues in the body once distributed by the blood.
Use of a blood agent as a weapon
During The Holocaust, the Nazis used a potent blood agent known as Zyklon B (hydrogen cyanide), as a replacement for carbon monoxide, to systematically murder Jews and other enemies of the Third Reich in death camp gas chambers. Zyklon B was mostly used because it has a quicker and deadlier effect on the body.