Medically Reviewed by Carmelita Swiner, MD on August 02, 2022
9 min read

A snakebite is an injury that happens when you’re bitten by a snake. A snakebite can be dangerous if a snake is venomous.

How snakes bite

Snakes that have venom have modified salivary glands. Venom is a form of saliva and probably evolved to help the reptile digest food. Some venom is more toxic than others and can be useful in killing prey.

During envenomation (the bite that injects venom or poison), the venom passes from the venom gland through a duct into the snake's fangs, and finally into its prey. Snake venom is made up of substances that have different effects.

In simple terms, these proteins can be divided into 4 categories:

  • Cytotoxins cause local tissue damage.
  • Hemotoxins cause internal bleeding.
  • Neurotoxins affect the nervous system.
  • Cardiotoxins act directly on the heart.

Which snakes bite

Two major families of snakes account for most venomous snakes dangerous to humans.

  • The elapid family includes the cobras; the mambas; the kraits (Bungarus) of Asia; the coral snakes (Micrurus) of the Americas; and the Australian elapids, which include the coastal taipan (Oxyuranus scutellatus), tiger snakes (Notechis), king brown snake (Pseudechis australis), and death adders (Acanthophis). Highly venomous sea snakes are closely related to the Australian elapids.
  • The viper family includes the rattlesnakes (Crotalus) (Western diamondback rattlesnake and timber rattlesnake); moccasins (Agkistrodon); and lance-headed vipers (Bothrops) of the Americas; the saw-scaled vipers (Echis) of Asia and Africa; the Russell's viper (Daboia russelii) of Asia; and the puff adder (Bitis arietans) and Gaboon viper (Bitis gabonica) of Africa.
  • Most species of the most widely distributed and diverse snake family, the Colubrids, lack venom that is dangerous to humans. But some species, including the boomslang (Dispholidus typus), twig snakes (Thelotornis), the Japanese garter snake (Rhabdophis tigrinus), and brown tree snake (Boiga irregularis), can be dangerous. Other members of this family, including American garter snakes, kingsnakes, rat snakes, and racers, are harmless to humans.

It has been estimated that up to 1.8 million snakebites occur worldwide each year, causing 20,000 to 94,000 deaths. Snakebites are more common in tropical regions and in areas that are mostly agricultural. In these areas, large numbers of people coexist with numerous snakes.

About five deaths occur per year from snakebites in the United States. People provoke bites by handling or even attacking snakes in a significant number of cases in the U.S. Of the estimated 45,000 snakebites per year in the U.S. about 8,000 are by venomous snakes.

Bites by venomous snakes result in a wide range of effects, from simple puncture wounds to life-threatening illness and death. The early effects of a venomous snakebite can be misleading. A victim can have no significant symptoms at first, and then suddenly have a hard time breathing and go into shock.

Signs and symptoms of snake poisoning can be broken into a few major categories:

  • Local effects: Bites by vipers and some cobras (Naja and other genera) are painful and tender. They can be severely swollen and can bleed and blister. Some cobra venoms can also kill the tissue around the site of the bite.
  • Bleeding: Bites by vipers and some Australian elapids can cause bleeding of internal organs such as the brain or bowels. A victim may bleed from the bite site or bleed spontaneously from the mouth or old wounds. Unchecked bleeding can cause shock or even death.
  • Nervous system effects: Venom from elapids and sea snakes can affect the nervous system directly. Cobra (Naja and other genera) and mamba (Dendroaspis) venom can act particularly quickly by stopping the breathing muscles, resulting in death without treatment. At first, victims may have vision problems, speaking and breathing trouble, and numbness.
  • Muscle death: Venom from Russell's vipers (Daboia russelii), sea snakes, and some Australian elapids can directly cause muscle death in multiple areas of the body. The debris from dead muscle cells can clog the kidneys, which try to filter out the proteins. This can lead to kidney failure.
  • Eyes: Spitting cobras and ringhals (cobra-like snakes from Africa) can actually eject their venom quite accurately into the eyes of their victims, resulting in direct eye pain and damage.

When to seek medical care

Any snakebite victim should go to a hospital emergency department unless the snake is positively identified by an expert as nonvenomous. Remember, misidentification of the snake species could be a fatal error.

Bites by nonvenomous species require good wound care. Victims should get a tetanus booster if they have not had one within the last 5 years.

A snakebite is diagnosed based on the history of the event. Identification or description of the snake would help, because not all snakes are venomous, and because there are different kinds of antivenom for different species of snakes. In Australia, the doctor may use a kit to determine the specific type of snake.

The doctor also looks for evidence of fang marks or local trauma in the area of the bite. Pain and swelling come with many snakebites.

  • The doctor treats breathing problems, shock, and/or immediately life-threatening injuries even before a full workup is complete.
  • The wound needs to be examined and cleaned.
  • The doctor will likely send blood and urine samples to a laboratory to look for evidence of bleeding, problems in the blood clotting system, kidney problems, or muscle death. These problems may not be apparent at first, but can have dire consequences if missed.
  • The victim is monitored to look for worsening symptoms at the wound site, or worsening symptoms in the breathing or cardiovascular systems.
  • A rare complication in very swollen limbs is compartment syndrome. Limbs are divided into compartments of muscles, blood vessels, and nerves. Severe swelling can cut off the blood circulation to a compartment. When the circulation is cut off, the victim usually has severe pain and numbness. Later, the limb may get white and cold. If not treated in time, the limb may need to be amputated.

Medical treatment

The doctor treats life-threatening conditions first. A victim who’s not breathing well may need a tube placed in their throat and a ventilator machine. People who are in shock require intravenous fluids and possibly other medicines to keep blood flowing to vital organs.

  • Antivenom: This is a kind of medicine that boosts the immune system. Doctors give it to victims with significant symptoms if appropriate and available. This therapy can be lifesaving or limb-saving. Antivenom can occasionally also cause allergic reactions, or even anaphylactic shock, a life-threatening type of shock that needs fast treatment with epinephrine and other medications.
  • Serum sickness: Antivenom can also cause this illness within 5-10 days of therapy. Serum sickness causes fevers, joint aches, itching, swollen lymph nodes, and fatigue, but it’s not life-threatening.
  • Monitoring: Even victims without significant symptoms need to be monitored for several hours, and some people need to be admitted to the hospital for overnight observation.
  • Wounds: The doctor cleans the wound and looks for broken fangs or dirt. A tetanus shot is required if the victim hasn’t had one within 5 years. Some wounds may require antibiotics to help prevent infection.
  • Surgery: Rarely, the doctor may need to consult a surgeon if there is evidence of compartment syndrome. If treatment with limb elevation and medicines fails, the surgeon may need to cut through the skin into the affected compartment, a procedure called a fasciotomy. This procedure can relieve the increased limb swelling and pressure, potentially saving the arm or leg.

Snakebite first aid

If you or someone you know is bitten by a snake, call 911 right away and try to stay calm. If you can describe the snake, that can help first responders figure out the right treatment.

Until help arrives, try to keep the bite below heart level and wash the area of the bite with warm, soapy water. Then cover it to keep it clean and dry.

Don’t drink anything caffeinated or any kind of alcoholic beverage as a painkiller.


Snakebite first aid myths

As important as knowing what to do is knowing what not to do. For example, while it’s good to have a description of the snake, you shouldn’t try to catch it.

As for treating someone’s bite, ignore some things you might have seen in the movies:

  • Don’t wrap it in a tourniquet.
  • Don’t open the area up with a knife or sharp object.
  • Don’t try to suck out the venom or put ice on it.

Follow-up care

A snakebite victim who has been released from the hospital should return to medical care immediately if their symptoms get worse, especially if they have trouble breathing, a change in mental status, evidence of bleeding, worsening pain, or worsening swelling.

Someone who has received antivenom treatment for a snakebite should return to medical care if any signs of serum sickness develop (fever, muscle or joint aches or swelling, hives). This complication usually occurs within 5-10 days after they get the antivenom.

A snakebite victim (particularly one who got a rattlesnake bite) should, for the first few weeks, warn their doctor of this fact before any routine or emergency surgery. Some snake venoms can make it hard for blood to clot for a week or more after the bite.

The snake is almost always more scared of you than you are of the snake. Giving the snake the opportunity to escape prevents most bites.

  • Don’t try to handle, capture, or tease venomous snakes or snakes of unknown identity.
  • Snakebites often go along with alcohol use. Drinking can weaken your inhibitions, making it more likely that you might attempt to pick up a snake. Alcohol also decreases your coordination, making a mishap more likely.
  • If you are outdoors, you can help prevent significant bites by wearing boots while hiking. Long pants can make a bite less severe. When in snake country, be cautious where you place your hands and feet (for example, when gathering firewood or collecting berries), and never walk barefoot after dark.
  • If your occupation or hobby exposes you to dangerous snakes on a regular basis, planning before a potential bite may save your life. Since not every doctor is familiar with snakebites and not every hospital has or knows how to get antivenom, providing information about the type of snake, type of venom, and getting and using antivenom can help the medical staff treat you.

Although the vast majority of victims bitten by venomous snakes in the United States do very well, predicting the prognosis in any individual case can be difficult. Even though there may be as many as 8,000 bites by venomous snakes every year, there are fewer than 10 deaths, and most of these fatal cases do not seek care for one reason or another. It is rare for someone to die before they are able to reach medical care in the United States.

Most snakes are not venomous if they bite. If you are bitten by a nonvenomous snake, you will recover. The possible complications of a nonvenomous bite include a retained tooth in the puncture wounds or a wound infection (including tetanus). Snakes do not carry or transmit rabies.

Not all bites by venomous snakes result in venom poisoning. In more than 20% of bites by rattlesnakes and moccasins, for example, no venom is injected. These so-called dry bites are even more common with bites by some of the elapids. Dry bites have the same complications as nonvenomous snakebites.

A victim who is very young, old, or has other diseases may not tolerate the same amount of venom as well as a healthy adult. The availability of emergency medical care and, most important, antivenom can affect how well the victim does.

Serious venom effects can be delayed for hours. A victim who appears well at first could still become quite sick. All victims possibly bitten by a venomous snake should seek medical care right away.