Jellyfish stings are common and mostly painful. In a majority of cases, if stung, you do not need to go to hospital or seek further medical advice. However, some jellyfish stings are dangerous and can cause a severe reaction, requiring emergency first aid.

Types of jellyfish sting

A sting occurs when a jellyfish’s tentacle touches a person’s skin. Stinging cells on the tentacles (called nematocytes) shoot poison into the skin, like tiny harpoons. The type of sting and how severe it is will depend on how much of the tentacle touched the skin and the species of jellyfish.

In northern Australian tropical waters, contact with major box jellyfish can cause a dangerous reaction. The venom is very potent and the tentacles are long and likely to come into contact with more of the skin.

Other jellyfish in northern waters can cause Irukandji syndrome, where a person experiences extreme pain in their body, not necessarily at the location of the sting. The reaction may not occur until half an hour after the jellyfish has stung. This type of sting can also be dangerous and requires emergency medical treatment.

The most common type of jellyfish sting comes from bluebottles (also called Portuguese Man-of-War), which are found all around the coastline of Australia. These stings are painful, but it’s rare to have to see a doctor about them.

Jellyfish sting symptoms

Major box jellyfish

Where the jellyfish tentacles have made contact with the person’s skin, there will usually be severe pain and a red or purple whip-like lesion. In rare cases, the person’s heart may stop, causing death. It's therefore very dangerous and risky to have contact with this jellyfish.

Other box jellyfish

Irukandji-like symptoms can occur 20-30 minutes after the sting and include:

• severe pain in the body (back, tummy, chest and muscles)
• increased heart rate (tachycardia)
• anxiety and sweating
• nausea and vomiting
• in rare cases, fluid in the lungs (pulmonary oedema)
• in rare cases, damage to the heart

Bluebottle and minor jellyfish

Stings by bluebottle jellyfish are the most common in Australia. These can cause intense pain and sores in the areas of skin which have been in contact with the jellyfish tentacles. The pain usually decreases or stops after 1–2 hours and the sores may fade after a few days. You may also have a rash or redness in the area which was stung.

Jellyfish sting treatment

It can be hard to know which species of jellyfish has stung you. Treat any sting as if it is a sting by a major box jellyfish or other box jellyfish if:

• it is in the tropics in Australia
• you aren’t sure what the jellyfish is
• there are multiple sting sites
• the person stung seems unwell

Major box jellyfish

Call triple zero (000) for an ambulance and start the following first aid:

• Put plenty of vinegar on the jellyfish stings. This stops any nematocytes that haven’t already fired venom from firing. If vinegar is not available, wash with sea water.
• Carefully remove the tentacles from the skin.
• If the person is unconscious, perform cardiopulmonary resuscitation (CPR)

Other box jellyfish

If Irukandji-like symptoms occur (as described above), call triple zero (000) for an ambulance then:

• Put plenty of vinegar on the jellyfish stings.
• Carefully remove the tentacles from the skin.

Bluebottle and minor jellyfish

• Wash the sting site with sea water and remove any tentacles.
• Immerse the sting or run hot water on the skin for 20 minutes. Make sure the hot water will not burn the person. It should be as hot as they can tolerate — around 45 degrees celsius. The person can also have a hot shower.
• If there is no hot water, an ice pack may help to relieve the pain.

Vinegar should not be used for bluebottle stings since it doesn’t help the sting and may increase the person’s pain.

Jellyfish sting prevention

Some things you can do to help prevent jellyfish stings are:

• Avoid swimming in the sea when warning signs about jellyfish are displayed.
• Don’t touch any jellyfish in the water or on the beach.
• Wear a full-body Lycra wetsuit and waterproof footwear

You can also swim near a lifeguard who will be able to give you first aid or, if your symptoms are severe, call an ambulance for you.

When to seek help

If you are stung in tropical waters and any of the above symptoms for box jellyfish or Irukandji-like symptoms occur, call triple zero (000) for an ambulance.

For bluebottle or minor jellyfish stings, seek advice from your local doctor if the pain continues.