What to Know About Box Jellyfish Stings

Medically Reviewed by Zilpah Sheikh, MD on March 27, 2024
Written by Alyson Powell Key
4 min read

Box jellyfish, also known as "stingers," are highly venomous aquatic animals. It has a body that looks like a box with lots of tentacles covered in venom-filled stingers. Jellyfish use stingers to protect themselves and kill prey. If you brush against a tentacle, the stingers pierce the skin and inject venom, which then enters your bloodstream. 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.

Where do box jellyfish live?

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.

Box jellyfish size

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.

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. 
  • Ask local residents and lifeguards about recent jellyfish sightings.
  • Look for a sign or flag warning of dangerous marine life (it may be purple).
  • Swim in areas with lifeguards.
  • Bring vinegar and tweezers to the beach to treat a potential jellyfish sting.

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

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

  • Burning pain in the skin
  • Welts in the skin, usually in a whip-like pattern
  • Tentacles from the jellyfish stuck onto the skin
  • Unusual behavior due to pain
  • Stomach pain 
  • Chest pain
  • Muscle pain or spasms
  • Sweating
  • Nausea or vomiting

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 15 centimeters or 6 inches, then the sting is likely dangerous.

While death from jellyfish stings is rare, it's more common with stings from box jellyfish. Up to 2 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 70 centimeters altogether, or around 2 feet, seek medical attention immediately because unconsciousness and death are likely to follow. 

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.
  • Pull out any tentacles on their skin using tweezers.
  • 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.

What not to do after a box jellyfish sting

  • Don't pee on a jellyfish sting; it could make the sting hurt worse.
  • Don't use cold, fresh water to rinse a sting.
  • Don't apply meat tenderizer, alcohol, ethanol, or ammonia.
  • Don't apply pressure bandages.
  • Don't rub the area where the sting happened.

 

Box jellyfish stings occur often in:

  • Tropical Australian waters between November and April
  • Adult men and people assigned male at birth swimming in water less than 100 meters deep (about 328 feet)
  • People swimming between 3 p.m. and 6 p.m. during an outbound tide
  • Children

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

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. 

Severe allergic reaction

Jellyfish stings can sometimes cause a severe allergic reaction that includes trouble breathing or swallowing. Call 911 right away if you or someone you know is having these symptoms.

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. 

Box jellyfish scars

While a jellyfish sting is likely to get better within a few hours, some can leave a rash that stays with you for weeks. After the rash fades, you could have a permanent scar.

Box jellyfish, known for their venom-filled tentacles, pose a threat in warm waters, particularly near northern Australia and the Indo-Pacific. To avoid stings, take steps such as avoiding swimming during jellyfish season, wearing protective clothing, and being cautious in shallow water. Symptoms of a sting include burning pain and whip-like welts on the skin. Severe stings can lead to Irukandji syndrome, which can cause back pain, muscle cramping, and nausea. Treatment for a box jellyfish sting involves applying vinegar to the sting and getting emergency help if necessary.