A box jellyfish is a potentially lethal marine animal found in the southern hemisphere’s Pacific Ocean. Steer clear of box jellyfish, as their stings can cause serious and sometimes fatal symptoms in a matter of minutes.

There are a few types of box jellyfish, and the largest type is particularly dangerous. It’s known as the Chironex fleckeri, and it’s about a foot wide, with tentacles up to 10 feet long.

The box jellyfish is difficult to see in the water because it’s translucent. It’s also an intentional swimmer, unlike most jellyfish that drift in the water.

Read on to learn more about box jellyfish stings, their treatment, and more.


Seek immediate medical treatment if you are stung by a box jellyfish.

Box jellyfish stings can be fatal because of the creature’s barbed tentacles containing venom. If you encounter these tentacles, the jellyfish can poison you with immediate effects.

Not all stings will cause death. But there isn’t a conclusive number of deaths from box jellyfish each year because some believe not all fatalities are reported. One study cites tens of deaths per year.

Another study examined box jellyfish stings on islands in Thailand, and found that of 15 cases, six were fatal. However, all of those stung experienced serious symptoms within a few minutes.

Symptoms from a box jellyfish sting will vary depending on the severity of your interaction with the creature.

You may notice these symptoms first:

  • severe stinging or burning pain
  • red skin wounds that look like caterpillar tracks

Symptoms will then escalate to:

  • disoriented behavior from pain
  • breathing difficulties
  • loss of consciousness
  • cardiac arrest

After just a few minutes, your symptoms may affect your cardiovascular, nerve, and muscle systems to such a great extent that you die.

A person stung by a box jellyfish needs immediate treatment. It’s important they get out of the water as soon as possible and receive first aid and life-saving interventions right away.

Once out of the water, make sure no part of the jellyfish remains on the person’s body. Use tweezers or another device to remove tentacles.

Rinse the area stung with vinegar for at least half a minute. This may stop the spread of the venom.

Call emergency medical responders. While you wait for them to arrive, monitor the person’s pulse and watch their breathing pattern.

If you notice that the person’s pulse or breathing is slowing, begin to administer CPR. Emergency responders may continue this resuscitation or administer oxygen using other equipment.

Once under medical care, the person stung by the box jellyfish may receive pain medication, antivenom, and continued treatment for breathing difficulties, including intubation and a ventilator.

First-aid treatments to avoid

You shouldn’t touch or compress the sting. Additionally, avoid rinsing the area with fresh water, alcohol, or ice packs. Application of these substances can make the sting worse.

There are a few ways to reduce the spread of venom administered by a box jellyfish.

Vinegar is recognized to be a helpful treatment for box jellyfish stings as first aid. In a study reviewing those stung by jellyfish who survived the encounter, half of them received a vinegar treatment.

Antivenom medications also exist for box jellyfish stings. Traditional antivenom comes from sheep. One researcher developed products called Sting No More using zinc and copper gluconate. Some doctors even apply heat to the sting.

A team of researchers identified one medication that not only blocks venom, but also reduces pain and scarring as long as you administer it within 15 minutes of the sting. It’s currently only available in injectable form.

A box jellyfish sting is very serious and may result in a variety of side effects.

Irukandji syndrome

This condition may result from a box jellyfish sting. It triggers stress and inflammation in your body. Symptoms may include pain, nausea, and even high blood pressure that can lead to a brain hemorrhage and possible death.


A sting may trigger your immune system to overreact and cause inflammation throughout your body.

Skin inflammation

You may experience dermatitis following a jellyfish sting that requires application of topical creams.


The tracks created from jellyfish stings along your skin may fade with time but leave a lasting scar.

Severe box jellyfish stings can be fatal, triggering cardiac arrest in your body within minutes. Less severe stings may only cause symptoms like pain and irritated red tracks along your body, but they may not be deadly.

It’s crucial to get treatment immediately following a box jellyfish sting to stop the spread of its venom, remove any remaining tentacles on your body, and get oxygen to support your body as it reacts to the poison.

Here are some ways to prevent a box jellyfish sting:

  • Avoid swimming or wading in areas with box jellyfish.
  • Talk to locals in swimming areas that are known to have box jellyfish to make sure there haven’t been recent sightings.
  • Look for any posted signs or warnings about box jellyfish and avoid potentially infested waters.
  • Wear a bodysuit or wetsuit to protect your skin when in the water.
  • Only use beaches that have lifeguards who may be able to help if you get stung.
  • Come prepared with first-aid supplies and information on what to do if you’re stung by a box jellyfish.

Box jellyfish stings can be very serious and deadly. Avoid swimming in areas where these creatures may be present. If you choose to swim in areas where box jellyfish live, make sure you use a beach that has trained lifeguards with proper first-aid materials.

If you’re stung by a box jellyfish, get out of the water and seek immediate treatment. Box jellyfish stings require quick emergency medical care.