Are Lizards Poisonous?[3 Poisonous Lizards Discussed]

Are Lizards Poisonous

If lizards freak you out like most other people, you must be wondering whether they are venomous or not 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.

Are lizards poisonous? Some species of lizards are very venomous, and their bite can incapacitate even a human being. Luckily most of these lizards are found in the wild. Most lizards found in houses and gardens are not poisonous to humans at all. House lizards are commonly called geckos.

Venomous lizards are mostly found in the wild and do not bite unless seriously provoked. There are very few reports of cases where these lizards have killed human beings.

Are Lizards Poisonous?

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

Reason being, lizards are cold blooded animals and get heat from their sorrounings.

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 poisonous: the Gila Monster and the Mexican Beaded Lizard.

Untill recently, when more research into lizards bites have revealed more information.

Among some of the newly discovored 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 of the toxins produced by both lizards and snakes have made scientists theorize that venomous lizards and snakes might have had a common ancestry.

Currently, scienitists have been able identify toxin producing glands in two lizards species belonging to the igunian and anguimorph lineages.

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

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 so as to aid in their hunting for food.

As oppossed to snakes that inject venom to their victims through their fangs, in 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.

They bite with tenacity, 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 a 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 lists Gila Monster as endangered. In fact Arizona state laws clearly state that it is illegal to collect or capture them, harass, kill, shoot, trap or hunt the Gila Monsters.

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

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

Females are generally bigger than the males, their heads are broader to males. Beaded Lizards 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 abut 30 species and several other subspecies.

Varanidae family is characetrized with 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 metres about 10 feet long and weighing more than 350 pounds like the Komondo Dragon.

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

Most the Monitor lizards 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 secnt of their prey like snakes do.

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

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

lets take a brief look at the Komondo dragon the largest living lizard.

Komodo Dragon (Varanus komodoensis)

Are Lizards Poisonous

Their name comes from the Komondo island in Indonesia where among other small insland these lizard inhabit.

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

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

Untill, a group of scientist found out that, Komondo Dragon actually has venom that it injects into its prey.

Komodo Dragon has about six glands of venom located on each side of the lower jaw. Combined these glands can hod as much as 1.2 millimeters 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 Taipan.

The venom of the Komondo Dragon causes the following effects to 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 preys, they still lack an efficient mode of delivery like snakes do, their venom delivery mode involves bitting 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, Nile Monitor mostly in Africa.

Asian Water Monitor or Two-banded Monitor (Varanus salvator) found in Bengal and Sri Lanka through 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 lizards 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?

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 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.

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 livespan of about 5 yeras. 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 area such as the urban areas where they can get enough food to sustain them.

Surprisingly enough, house geckos can also be kept as pets in vivariums that has 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 snakes.

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 lizards bites are not poisonous to humans at all. However, wild lizards bites can be very poisonous, 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 lizards bite are not poisonous, poisonous lizards bites exhibits the following symptoms.

  • oderate to severe bleeding.
  • Throbbing or burning pain.
  • Swelling that 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 off well iguansa 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 lizards is mentioned. So, black lizards could not be poisonous though more research is required in that subject.


While geckos or house or wall lizardss 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 pet, 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 it may have some adverse health effect that may be life-threatening if not taken care of immediately.


My Name is Moffitoh, I operate a pet shop which deals in various pets such as reptiles, snakes, birds and Ornamental fish and plants. I also hold Bsc. degree in Applied Aquatic Science currently pursuing a Master's degree in Fish Pathology. This blog is a collection of answers to questions I encounter daily while dealing with Pets and Pets customers at the store.

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