Poison secreted by an animal, produced by specialized glands often associated with spines, teeth, or stings. It may be primarily for paralyzing or killing prey or may be purely defensive. Some venoms also function as digestive fluids. Their effects can range from localized skin inflammation to almost immediate death; they include nervous-system excitation (cramps, vomiting, convulsions) or depression (paralysis, respiratory or cardiac depression or arrest), hemorrhage, red-blood-cell breakdown, circulatory collapse, and allergic reactions (including hives and inflammation). Many major groups of animals contain venomous species: snakes (cobras, mambas, vipers, pit vipers); fish (stingrays, spiny sharks, certain catfish, puffers); lizards (Gila monsters, beaded lizards); scorpions; spiders (black widow spiders, brown recluse spiders); social insects (bees, wasps, some ants); and marine invertebrates (sea anemones, fire corals, jellyfish, sea urchins). Seealso antidote.
Learn more about venom with a free trial on Britannica.com.
Venom is any of a variety of toxins used by certain types of animals, for the purpose of defense and hunting. Generally, venom is injected by such means as a bite or a sting, while a poison is absorbed by ingestion or through the skin.
The animals most widely known to use venom are snakes, some species of which inject venom into their prey through hollow fangs; spiders and centipedes, which also inject venom through fangs; scorpions and stinging insects, which inject venom with a sting (which, in insects such as bees and wasps, is a modified egg-laying device – the ovipositor). Many caterpillars have defensive venom glands associated with specialized bristles on the body, known as urticating hairs, and can be lethal to humans (e.g., that of the Lonomia moth). Venom is also found in a few reptiles besides snakes, such as the gila monster and Mexican beaded lizard. Other insects, such as true bugs and many ants, also produce venom. Venom can also be found in some fish, such as the cartilaginous fishes – stingrays, sharks, and chimaeras – and the teleost fishes including monognathus eels, catfishes, stonefishes and waspfishes, scorpionfishes and lionfishes, gurnard perches, rabbitfishes, surgeonfishes, scats, stargazers, weevers, carangids, saber-toothed blenny, and toadfish. In fact, recent studies have shown that there are more venomous ray-finned fishes than all other venomous vertebrates combined. There are many other venomous invertebrates, including jellyfish and cone snails. The box jellyfish is widely considered the most venomous creature in the world. Some mammals are also venomous, including solenodons, shrews, the slow loris, and the male platypus.
Because they are tasked to defend their hives and food stores, bees synthesize and employ an acidic venom (apitoxin) to cause pain in those that they sting, whereas wasps use a chemically different venom designed to paralyze prey, so it can be stored alive in the food chambers of their young. The use of venom is much more widespread than just these examples, of course.
Doctors treat victims of a venomous bite with antivenin, which is created by dosing an animal such as a sheep, horse, goat, or rabbit with a small amount of the targeted venom. The immune system of the subject animal responds to the dose, producing antibodies to the venom's active molecule; the antibodies can then be harvested from the animal's blood and applied to treat envenomation in others. This treatment can be used effectively only a limited number of times for a given person, however, as that person will ultimately develop antibodies to neutralize the foreign animal antibodies injected into him (anti-antibody antibodies). Even if that person does not suffer a serious allergic reaction to the antivenom, his own immune system can destroy the antivenin before the antivenin can destroy the venom. Though most people never require even one treatment of antivenin in their lifetime, let alone several, people who work with snakes or other venomous animals may.
Aristolochia rugosa and Aristolochia trilobata, or "Dutchman's Pipe," are recorded in a list of plants used worldwide and in the West Indies, South and Central America against snakebites and scorpion stings. Aristolochic acid inhibits inflammation induced by immune complexes, and nonimmunological agents (carrageenan or croton oil). Aristolochic acid inhibits the activity of snake venom phospholipase (PLA2) by forming a 1:1 complex with the enzyme. Since phospholipase enzymes play a significant part in the cascade leading to the inflammatory and pain response, their inhibition could lead to relief of problems from scorpion envenomation.