All species in the genus
Naja are capable of delivering a fatal bite to a human. Most species have strongly
neurotoxic venom, which attacks the nervous system, causing paralysis, but many also have
cytotoxic features that cause swelling and
necrosis, and have a significant anticoagulant effect. Some also have
cardiotoxic components to their venom. Several
Naja species, referred to as
spitting cobras, have a specialized venom delivery mechanism, in which their
front fangs, instead of ejecting venom downward through an elongated discharge orifice (similar to a
hypodermic needle), have a shortened, rounded opening in the front surface, which ejects the venom forward, out of the mouth. While typically referred to as "spitting", the action is more like squirting. The range and accuracy with which they can shoot their venom varies from species to species, and it is used primarily as a defense mechanism. The venom has little or no effect on unbroken skin, but if it enters the eyes, it can cause a severe burning sensation and temporary or even permanent blindness if not washed out immediately and thoroughly. A recent study showed that all three spitting cobra lineages have evolved higher pain-inducing activity through increased
phospholipase A2 levels, which potentiate the pain-inducing action of the cytotoxins present in most cobra venoms. The timing of the origin of spitting in African and Asian
Naja species corresponds to the separation of the human and
chimpanzee evolutionary lineages in Africa and the arrival of
Homo erectus in Asia. The authors therefore hypothesize that the arrival of bipedal, tool-using primates may have triggered the evolution of spitting in cobras. The
Caspian cobra (
N. oxiana) of Central Asia is the most venomous
Naja species. According to a 2019 study, the
murine via
intravenous injection value for
Naja oxiana (Iranian specimens) was estimated to be 0.14 mg/kg (0.067-0.21 mg/kg) more potent than the
sympatric Pakistani
Naja naja karachiensis and
Naja naja indusi found in far north and northwest India and adjacent Pakistani border areas (0.22 mg/kg), the
Thai Naja kaouthia (0.2 mg/kg), and
Naja philippinensis at 0.18 mg/kg (0.11-0.3 mg/kg).
Latifi (1984) listed a subcutaneous value of 0.2 mg/kg (0.16-0.47 mg/kg) for
N. oxiana. The
Banded water cobra's was estimated to be 0.17 mg/kg via IV according to Christensen (1968). The
Philippine cobra (
N. philippinensis) has an average murine of 0.18 mg/kg IV (
Tan et al, 2019). The
Samar cobra (
Naja samarensis), another cobra species endemic to the southern islands of the Philippines, is reported to have a of 0.2 mg/kg, similar in potency to the
monocled cobras (
Naja kaouthia) which also have a of 0.2 mg/kg. The
spectacled cobras that are
sympatric with
N. oxiana, in Pakistan and far northwest India, also have a high potency of 0.22 mg/kg. Other highly venomous species are the forest cobras and/or water cobras (
Boulengerina subgenus). The murine intraperitoneal of
Naja annulata and
Naja christyi venoms were 0.143 mg/kg (range of 0.131 mg/kg to 0.156 mg/kg) and 0.120 mg/kg, respectively. Christensen (1968) also listed an
IV of 0.17 mg/kg for
N. annulata. The Chinese cobra (
N. atra) is also highly venomous. Minton (1974) listed a value of 0.3 mg/kg intravenous (IV), The of the
Cape cobra (
N. nivea) according to Minton, 1974 was 0.35 mg/kg (IV) and 0.4 mg/kg (SC). --> The
Senegalese cobra (
N. senegalensis) has a murine of 0.39 mg/kg (Tan et al, 2021) via IV. The
Egyptian cobra (
N. haje) of
Ugandan locality had an IV of 0.43 mg/kg (0.35–0.52 mg/kg). ==Medical importance==