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What to Know About Box Jellyfish Stings

Medically Reviewed by Dan Brennan, MD on June 09, 2021

Box jellyfish, also known as 'stingers', are a highly venomous aquatic animal. Prevention is key, but learning the symptoms before a beach vacation can help you get fast treatment. Their sting can cause paralysis and, in some cases, death.

What Is a Box Jellyfish?

A box jellyfish has a body that looks like a box with lots of tentacles covered in venom-filled stingers. Box jellyfish live in warm waters all over the world, but the most dangerous kinds are found near the coasts of northern Australia and the Indo-Pacific region.

The Australian box jellyfish is the biggest and most venomous species and has tentacles up to 10 feet long. Unlike other kinds of jellyfish, box jellyfish can swim and see. They mainly eat shrimp and small fish.

Jellyfish use stingers to protect themselves and kill prey. If you accidentally brush against a tentacle, the stingers pierce into the skin and produce venom, which then enters the bloodstream. 

Preventing a Box Jellyfish Sting

Take the following precautions to prevent getting stung by a box jellyfish:

  • Avoid swimming near tropical coastlines during jellyfish season, which is between November and April.
  • Wear a wetsuit or other protective clothing when swimming or diving.
  • Wear waterproof sandals or shoes when walking through shallow water. 
  • Stamp and scrape your feet to make sea creatures aware of your presence.
  • Don't touch dead jellyfish that have washed up on shore. 

Rainy and windy weather can deter box jellyfish, so it's better to swim in these conditions than on a sunny day. 

Symptoms of a Box Jellyfish Sting

Box jellyfish are commonly found in waters off the tropical Australian coast. Take extra care when swimming in these areas. The main symptoms and signs of a box jellyfish sting include:

  • Burning pain in the skin
  • Welts in the skin, usually in a "whip" pattern
  • Tentacles from the jellyfish stuck onto the skin
  • Unusual behavior due to pain

Whether a sting is serious depends on the size of the jellyfish. If the main body, known as the bell, of a box jellyfish measures over 15cm, then the sting is likely dangerous.

Symptoms of Irukandji Syndrome

While death from jellyfish stings is rare, it's more common with stings from box jellyfish. Up to two hours from the sting, you may develop a life-threatening condition called Irukandji syndrome. The symptoms include:

If the length of the welts on the skin measure over 70cm altogether, or around two feet, seek medical attention immediately because unconsciousness and death are likely to follow. 

Treatments for a Box Jellyfish Sting

If a box jellyfish stings someone, take the following measures:

  • Take the person out of the water carefully
  • Apply vinegar to the sting for 30 seconds
  • Check the person's pulse and breathing regularly
  • Call an ambulance in case of an emergency

Many beaches in Australia have clearly marked stations offering vinegar for the public for this very creature. But if you don't have access to vinegar, you should remove any tentacles from the sting carefully before washing the area with seawater. Start resuscitation if the person has stopped breathing.

Risk Factors for a Box Jellyfish Sting

Box jellyfish stings occur often in:

  • Tropical Australian waters between November and April
  • Adult men swimming in water less than 100m deep
  • People swimming between 3 PM and 6 PM during an outbound tide
  • Children

Around 37% of strings occur in children, who are most vulnerable to stings because of their smaller bodies.

Complications of a Box Jellyfish Sting

Complications of a box jellyfish sting may include a delayed sensitivity reaction, which can happen a week or two after a sting and cause the following symptoms at the affected site:

  • Blisters
  • Rashes
  • Skin irritation

Minor stings can be treated at home with ice packs, pain medication, antibiotic ointments, and bandages. 

If you've had a severe reaction, you may be in the hospital for a few days for treatment with antivenom, which is an immunizing agent that can only be given under a doctor's supervision. 

WebMD Medical Reference

Sources

SOURCES:

DermNet NZ:  "Australian Box Jellyfish Stings."

Mayo Clinic: "Jellyfish Stings", "Antivenin (Crotalidae) Polyvalent (Injection Route)."

National Ocean Service: "What is the most venomous marine animal?" 

Queensland Ambulance Service: "Box Jellyfish."

StatPearls: "Irukandji Syndrome." 

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