To make an antivenin, small doses of poison are injected into horses or goats. The amount of toxin is not enough to kill the animal but is enough to trigger the production of antibodies. These are specialized proteins which recognize the toxin and neutralize it. As the dosage given to the animal is increased, more and more antibodies are generated. Blood is then removed and the antibodies are isolated from the serum. Recent research in India has shown that chickens can also be used. Again, small doses of the venom are injected, but this time the antibodies are isolated not from the chicken’s blood, but from the eggs it lays. The process is more economical than using horses or goats and seems to be associated with fewer side effects. The main worry about using antivenin is the possibility of an allergic reaction. The extraction of antivenin from plasma is not a perfect process and various cellular components are extracted along with the desired antibodies. These are foreign to humans and can cause severe allergic reactions, including anaphylaxis. That’s why, time permitting, allergy tests are performed before the antivenin is injected. Antivenins are not available for all snake poisons and they do not always work.