Irukandji Syndrome – The Box Jellyfish (It’s Serious!)

Symptoms of Irukandji Syndrome

The symptoms of Irukandji syndrome can be life-threatening. If you or someone around you is stung, call emergency services immediately (911 in North America; 000 in Australia). Pour vinegar or seawater on the wound to deactivate and wash off any remaining tentacles on the victim. If the victim is unconscious, immediately remove them from the water — ask if anyone is qualified to perform emergency CPR. Other countries may have different codes. If you are abroad, always ensure you know the code for emergency services prior to traveling. .

When Irukandji jellyfish sting, the venom activates a mechanism in the brain called sodium channels. This allows a sodium to enter, and as a result activates the person’s fight or flight hormones (epinephrine and norepinephrine). 

Symptoms include, but are not limited to:

Credit: Meg Newman
  • Instantaneous Severe Pain
    • Once stung by a jellyfish, in some species, the pain can be instantaneous. With the pain being felt within seconds.  
  • Headache
  • Anxiety
  • Back pain
  • Hypertension: High Blood Pressure
  • Tachycardia: Increased Heart Rate
  • Acute Heart Failure
    • This can either occur by two methods: stress induced or pores forming on the cell membranes of the heart. When pores form on the cel membranes of the heart, they allow toxins from the venom to enter in and cardiac enzymes out. This results in the heart’s cells failing.

Irukandji Syndrome Treatment & Prevention


  • URINATING ON WOUND: This is an old wives tale. Urinating on the wound can make things worse. It can activate any nematocysts on the skin, releasing more venom into the victim.
  • POUR FRESH (DRINKING) WATER ON THE WOUND: Using drinking/fresh water to remove any remaining tentacles is a bad idea. If this 
  • TAKING BETA BLOCKERS: Using a beta-blocker can result in the opposite effect, instead of having hypertension it can result in severe hypotension (severe low blood pressure.


  • Pour Household Vinegar for at least on a wound to deactivate any remaining tentacles
  • If there is no vinegar, gently pour sea water on the wound to attempt to remove any nematocysts remaining on the skin. DO NOT TOUCH THE WOUND.
  • Healthcare professionals may use Benzodiazepines and/or Nitroglycerin. Always keep a well-documented record of any prescription medications and health history handy in case of an emergency/


  • The best prevention is to abstain from swimming or doing any recreational marine activities where these jellyfish are normally present — especially during months where they are most likely to be present.
  • Wearing a full body lycra suit (wet-suit) will give a barrier between the jellyfish and the person. This isn’t guaranteed to prevent a sting — any exposed area will result in the full effect. However, this will greatly reduce the risk of being stung in the water when conducting marine activities.

What are Irukandji Jellyfish

A popular name for the jellyfish scientifically known as Carukia barnesi. This popular name was given to this species of jellyfish, specifically, because it is the most common cause of the syndrome known as Irukandji Syndrome. There are over 25 different species of jellyfish which are known to cause Irukandji syndrome. 

These jellyfish range in size with C. barnesi being as small as 2cm in diameter making them resistant to barriered enclosures which prevent other species of jellyfish from entering. To give a better idea on just how small they are, they are roughly as small as an American penny or dime. Approximately, 50 to 100 people in Australia end up in the hospital due to being stung by a jellyfish.

Due to being inexperienced with the surrounding environment, tourists are more likely to be stung by jellyfish than those who are native to the regions where these jellyfish are endemic to. A jellyfish barrier may lull a sense of security.

Where Do Irukandji Jellyfish Stings Occur

These stings occur during recreational marine activities (swimming, snorkeling, surfing, etc). The jellyfish that are associated with Irukandji syndrome occur in the more northern regions of Australia. It is a misconception that this syndrome is endemic (only located in Australia). There are reports of syndromes with characteristics similar to Irukandji syndrome in areas such as south east Asia, tropical American states (e.g. Florida, Hawaii) Caribbean countries. In Australia, jellyfish season typically occurs from late October through to June.

How They Sting

These species of jellyfish have specialized cells called nematocysts. These nematocysts are developed by the jellyfish to catch food and protect themselves. When the jellyfish comes into physical contact with a person’s skin, the jellyfish’s nematocysts turn inside out resulting in a penetrating protrusion. Once it penetrates the skin it hooks on sort of like a harpoon. Then the jellyfish releases venom into the victims skin. 

It is more likely that the victim will not see the jellyfish, especially a species such as the “Irukandji” jellyfish C. barnesi as they are too small to quickly see or identify. Remember their diameter is only the size of an American penny.


Kong, E.L.; Nappe, T.M. Irukandji Syndrome. StatPearls Publishing. 2022. accessed Dec 2022.

This is a profile picture of Andy Chmait which contains 4 different pictures in one. 

On the top left Andy is holding a baby in snorkelling gear with the ocean and a railing in the background. 

The top right photo is Andy standing on a unique rock formation with the sky and ocean in the background. 

The bottom left photo is of Andy standing underneath a massive entry way with the beach and ocean in the background. 

The bottom right is of Andy on the beach at sunset with vibrant yellow skies reflecting on the ocean and sand.

Andy Chmait is a medical and scientific communications writer and videographer. He specializes in neurological and developmental disorders, nutrition and fitness, and genetics. Andy also has an interest in learning more in a wide variety of different fields in medicine and science. Learn more about Andy here.

Are you looking for a medical or scientific communications writer? Contact us today, and learn more about our medical + scientific communications services.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: