Snake venom is highly modified saliva that is produced by special glands of certain species of snakes. The gland which secretes the zootoxin is a modification of the parotid salivary gland of other vertebrates, and is usually situated on each side of the head below and behind the eye, invested in a muscular sheath. It is provided with a large alveoli in which the venom is stored before being conveyed by a duct to the base of the channeled or tubular fang through which it is ejected. Snake venom is a combination of many different proteins and enzymes. Many of these proteins are harmless to humans, but some are toxins.
Snake venoms are generally not dangerous when ingested, and are therefore not technically poisons.
Snake venom consists of proteins, enzymes, substances with a cytotoxic effect, neurotoxins and coagulants.