Skip to Content

Are Lizards Poisonous?[3 Venomous Lizards Discussed]

Are Lizards Poisonous?[3 Venomous Lizards Discussed]

DID YOU KNOW there is a big difference between VENOM and POISON? If lizards freak you out like most of us, you must be wondering whether they are venomous or poisonous especially if you spot them in your garden or house. Well, I did some digging to answer those concerns since my daughter freaks out whenever she sees a lizard.

But before we go into whether lizards are poisonous or not, let us first understand what the terms venomous and poisonous mean.

What is the Difference Between Venom and Poison?

Poison and venom are described as toxic substances that are secreted by animals to either protect themselves or to catch prey, however, the mode of delivery of these two toxic substances is very different and it is what differentiates them.

So, what is the difference between venom and poison?

Venom is delivered through a bite or sting. Venom can either serve as a defense mechanism or a way of incapacitating prey. A good example of a venomous animal is a snake, which uses its fangs to deliver deadly venom.

On the other hand, poison is delivered through the skin via indirect or passive means. Poison is mostly used as a defense mechanism against predators.

Most poisonous animals are brightly colored to warn would-be predators.

Types of Venom

Venom Description
NeurotoxicTargets the nervous system of the victim
HemotoxicAffects the blood clotting of the victim
MyotoxicDamages the muscles of the victim
cytotoxicDamages the cell of the victim

Are lizards poisonous or venomous?

There are no known lizards that are poisonous however, there are a few species of lizards that are venomous such as Gila monsters, Mexican beaded lizards, and the Komodo dragon. These venomous lizards deliver their venom via a bite. While their bite is painful it can cause human death if not treated. Symptoms of a lizard bite include swelling, pain, headache, sweating, thirst, and lymph nodes that may get swollen.

House lizards or geckos or garden lizards are not venomous or poisonous or harmful to humans. However, touching them could lead to a salmonella infection especially if they are from the wild.

Venomous lizards are mostly found in the wild and do not bite unless seriously provoked.

Are lizards poisonous or venomous to humans?

Lizards are not poisonous to humans but there are species of lizards that are venomous to humans such as Gila Monsters, Mexican beaded lizards, and Komodo Dragon. They deliver their venom through a bite, while this bite can be painful to humans it has not been known to cause death.

There are more than 5,000 species of lizards globally. Distributed among all the continents apart from Antarctica where it is believed that there are no lizards. Source

Given that lizards are cold-blooded animals and get heat from their surroundings. It is therefore close to impossible for them to survive in zones that are always cold all year round.

For a long time scientists, have been believing that there are only two species of lizards that are venomous: the Gila Monster and the Mexican Beaded Lizard.

Until recently, when more research into lizards bites has revealed more information.

Among some of the newly discovered venomous lizards are two species that are commonly kept as pets in the United States.

Nine types of toxins produced by lizards are very similar to the ones produced by snakes. More toxins are being studied by scientists to be compared to those of snakes.

These similarities in the toxins produced by both lizards and snakes have made scientists theorize that venomous lizards and snakes might have had a common ancestry.

Currently, scientists have been able to identify toxin-producing glands in two lizard species belonging to the iguanian and anguimorph lineages.

These scientists believe that there are about 100 species of lizards that use venom.

3 Examples of Venomous Lizards



For a long time, the two most venomous lizards came from the Helodermatidae family and genus Heloderma.

These species of lizards are the Mexican Beaded Lizard and Gila Monster. Both of these lizards are carnivorous which makes scientists believe that they developed venom to aid in their hunting for food.

As opposed to snakes that inject venom into their victims through their fangs, lizards’ venom just flows into the wounds they inflict.

Fortunately, these lizards have not been known to attack human beings. A fact that can be attributed to the fact that they are mostly found in the wild.

Are Lizards Poisonous?[3 Venomous Lizards Discussed]
Mexican Beaded Lizard

They bite with tenacity, and venom from these species of lizards causes breathing difficulties, convulsions, and paralysis, however, this venom is not dangerous to humans.

Both Gila Monsters and Beaded Lizards live for up to about 30 years in the wild and become mature sexually at the age of 2 to 3 years.

The Gila Monster mates around April while the Beaded Lizard mates around May or June with eggs being laid two months after the date of mating.

Both Gila Monster and Beaded Lizards eggs hatch within five and half months to seven months.

Anguimorphs Geographical Distribution

Gila Monster (Heloderma suspectum) is normally found in Sonoran and Chihuahuan deserts, in the Mojave, New Mexico, and Mexico, and southern Arizona.

An adult Gila Monster can grow as big as 55 cm (22 inches). They have tuberculated skin, a broad head with a stout body, stumpy tail. Their body is lined with bright patches varying from orange to yellow or salmon.

Both United States and Mexico list Gila Monster as endangered. In fact, Arizona state laws clearly state that it is illegal to collect or capture, harass, kill, shoot, trap or hunt the Gila Monsters.

Are Lizards Poisonous?[3 Venomous Lizards Discussed]
Gila Monster (Heloderma suspectum) Credits

The Beaded Lizards on the other hand are widely distributed in Western and Central Mexico, mostly loaming the pine and tropical forests, and thorn scrubland.

The Beaded Lizards are very similar to the Gila Monster but a bit bigger, an adult Beaded Lizard can be as big as 1 meter or 40 inches.

Females are generally bigger than males, their heads are broader than males. The beaded Lizard’s body is brown but bears some bright whitish or yellow spots.

Just like Gila Monsters Beaded lizards are also protected by the law as they are considered endangered.

Monitor Lizards (Varanidae)

The family Varanidae consists of about 30 species and several other subspecies.

Varanidae family is characterized by a long, smooth, retractile tongue, long snout, strong claws and limbs that are well developed, dull grayish body color, and a long tail.

Unlike their relatives, the Gila and Beaded Lizards, Monitor lizards come in different sizes with some being as small as 20cm about 2 to 3 feet and some measuring as much as 3 meters about 10 feet long, and weighing more than 350 pounds like the Komodo Dragon.

The geographical distribution of monitor lizards is varied, most of the monitor lizards are found in Australia which hosts about 17 species, and Asia and Africa which hosts about 3 species.

Are Lizards Poisonous?[3 Venomous Lizards Discussed]
Monitor Lizards (Varanidae)

Most of the Monitor lizard species have become semi-aquatic, meaning you will most likely find them near a water source.

They are carnivorous and use their tongue to detect the scent of their prey as snakes do.

Despite being added to the list of venomous lizards, these lizards are kept as pets in most parts of the world, especially in the United States and there has been no case of death caused by these lizards recorded so far.

Generally, monitor lizards avoid confrontation and will only result in aggression when forced to, and even so they will always make a warning before attacking.

let’s take a brief look at the Komodo dragon the largest living lizard.

Komodo Dragon (Varanus komodoensis)

Are Lizards Poisonous

Their name comes from the Komodo island in Indonesia which among other small islands these lizards inhabit.

They can feed on almost any meat that comes their way, and surprisingly enough for an animal their size they can run very fast. They can maim and kill large animals such as water buffalo, pigs, deer, and goats.

There have been very cases of human attacks by Komodo Dragons. For a long time, scientists used to believe that Komodo Dragon saliva contained some bacteria that when it bites its prey are left in the wound, and with time these bacteria kill the prey.

Until, a group of scientists found out that, Komodo Dragon actually has venom that it injects into its prey.

Are Lizards Poisonous?[3 Venomous Lizards Discussed]
Komodo Dragon (Varanus komodoensis)

Komodo Dragon has about six glands of venom located on each side of the lower jaw. Combined these glands can hold as much as 1.2 millimetres of venom, These glands are interconnected with several ducts to the teeth.

The venom responsible for decreased blood pressure was found to be very similar to one of the most lethal snakes in Australia called the Taipan.

The venom of the Komodo Dragon causes the following effects on its prey or victim,

  • Reduced blood pressure
  • Increases blood loss
  • sends a victim into shock, reduces mobility

Despite having a deadly venom reserve for their prey, they still lack an efficient mode of delivery like snakes do, their venom delivery mode involves biting and pulling.

However, despite this venom being deadly to Komodo Dragons preys. It is not as deadly to humans, only causing a mild effect.

Other monitor lizards with less dangerous monitors include Lace Monitor (Varanus varius) that includes African Savannah Monitor, or Savannah Monitor, Rock Monitor, White-throated Monitor, and Nile Monitor mostly in Africa.

Asian Water Monitor or Two-banded Monitor (Varanus Salvator) is found in Bengal and Sri Lanka throughout Southeast Asia.

The last venomous lizard is the Iguanidae Family. Yes, I know you are surprised, I was too.

However, here is the good news, this lizard’s venom is not deadly to humans at all compared to its prey. That is why you can easily keep iguanas as pet lizards without harm. Their venom secretion is very small. Source.

Are House Lizards Poisonous or venomous?

The common house gecko goes by the scientific name, Hemidactylus frenatus. It also goes with other common names such as the wall gecko, pacific house gecko, moon lizard, Asian house gecko, or house gecko.

The house gecko is not the only gecko in existence. There are other species of gecko that exist, however, the house gecko Hemidactylus frenatus is the most common and most invasive.

It is believed to have come from South East Asia, it is very invasive and can easily displace other gecko species within a short time.

Fortunately, house geckos are not poisonous or venomous to human beings at all. Overall, most geckos are nocturnal. They normally hide during the day and will appear at night to feed on insects and spiders.

Are Lizards Poisonous?[3 Venomous Lizards Discussed]
Common house gecko Hemidactylus frenatus

You will mostly find them hanging around porchlight or any source of light for that matter where insects are attracted to light.

House Geckos, grow to about 3 to 6 inches and have a lifespan of about 5 years. They will only bite when under distress, otherwise if they are under any threat they are very quick to retreat into their hiding.

House or wall geckos prefer, a warm, humid areas such as urban areas where they can get enough food to sustain themselves.

Surprisingly enough, house geckos can also be kept as pets in vivariums that have to be equipped with a heat source, hiding spaces, and most all a humidifier. House geckos can also serve as food for your pet snake, especially when they are bred.

Never feed your pet snake any wild-caught gecko as it may carry diseases or parasites that can harm your pet snake.

Frequently Asked Question

Are lizards harmful to humans? Most species of lizards found in close proximity to humans are not harmful at all. However, species found in the wild can be very harmful to humans and some could even kill a human being such as Komodo Dragon. Gila Monster and Beaded Lizard. House lizards are completely non-venomous to humans.

Is lizard bite poisonous? House or wall lizard bites are not poisonous to humans at all. However, wild lizard bites can be very venomous, though they affect humans mildly.

Do house lizards bite? House lizards do bite when provoked or when cornered. The first instinct of house lizards is to run and hide, but when cornered they will bite. But the bite is not poisonous at all.

How do you know if a lizard is poisonous? While most house lizard bite is not poisonous, poisonous lizard bites exhibit the following symptoms.

  • Moderate to severe bleeding.
  • Throbbing or burning pain.
  • Swelling gradually gets worse over several hours.
  • Teeth left in the wound.
  • Weakness.
  • Dizziness.
  • Nausea and vomiting.
  • Profuse sweating.
  • Trouble breathing.
  • Symptoms of a severe allergic reaction

Is the Komodo dragon poisonous? Komodo dragon is very venomous, their bites have been known to kill their prey within days. However, komodo dragon poison only causes mild effects on humans.

Are iguanas dangerous to humans? Despite being classified as venomous, iguanas venom is very little and harmless to humans. In fact, when taken care of iguanas can make a great pet lizard for humans.

Do house lizards attack humans? House lizards are docile and will only attack humans when provoked or cornered, nonetheless, the bite is non-venomous.

Are geckos lizards? Yes, geckos are lizards that belong to the Gekkota infraorder. Did you know geckos cannot blink?

Are black lizards poisonous? Based on all the lizards that were proven to be poisonous, there was no single black lizard is mentioned. So, black lizards could not be poisonous though more research is required on that subject.

Are backyard lizards poisonous? No, backyard lizards are not poisonous or venomous at all. However, they have been known to carry salmonella in their body, and touching them bare hard can cause a salmonella infection.


While geckos or house or wall lizards are not poisonous to humans at all if beaten and you experience some severe symptoms which you did not have prior to the bite you should consult your doctor immediately.

As far as you do not provoke the gecko in your house or corner, it is unlikely to bite you. Geckos are docile and can make a great pets, the reason they are in your house is to keep the insect population under control. If you cannot stand them have fumigators help you get rid of them.

However, just because house lizards are not poisonous does not mean that all lizards are not poisonous, actually, izards such as komodo dragon, Gila monsters, and Beaded Lizards are very venomous, even though their venom may not kill you may have some adverse health effect that may be life-threatening if not taken care of immediately.