Are all jellyfish stings dangerous?

Jellyfish stings are common and most of them are painful but not dangerous. However, some jellyfish stings are dangerous and can cause a severe reaction or even death. It's important to know what to look out for.

How does a jellyfish sting happen?

A sting occurs when a jellyfish's tentacle touches a person's skin. Stinging cells on the tentacle (called nematocysts) shoot poisonous venom into the skin.

How severe the sting is depends on the species of jellyfish and how much of the tentacle touched the skin.

What types of jellyfish are there in Australia?

Dangerous jellyfish can be found in Northern Australian tropical waters. The most dangerous is the major box jellyfish. Its venom is very poisonous, and its tentacles are long and likely to touch more of the skin.

Other types of box jellyfish in Northern Australian waters can cause Irukandji syndrome. This is 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 be dangerous and requires emergency medical treatment. These types of jellyfish are small and their sting may not be noticed at first.

The most common type of stinging jellyfish is the bluebottle. These are found in non-tropical areas, especially along the south-eastern coastline of Australia. Their stings are painful, but they don't usually need medical treatment.

What does a jellyfish sting feel like?

Major box jellyfish

Where the jellyfish tentacles have touched the skin, there will be immediate severe pain and red whip-like lines.

If there has been a large area of contact, the person's heart may stop, causing death. This can happen within a few minutes. Children are at especially high risk because they are smaller.

Other types of box jellyfish

The sting itself is usually mild. Irukandji-like symptoms can occur 20 – 30 minutes after the sting and include:

• severe pain in the body (back, abdomen and chest)
• increased heart rate (tachycardia)
• trouble breathing
• anxiety and sweating
• nausea and vomiting

Sometimes, a sting can cause fluid in the lungs and damage to the heart.

Bluebottle jellyfish

Bluebottle jellyfish stings can cause intense pain, whip-like lines and sores in the areas of skin that have been in contact with the jellyfish tentacles. The pain usually decreases or stops after 1 – 2 hours and you may have joint aches afterwards. You may also have a rash or redness in the area that was stung.

Sometimes these stings can cause an allergic reaction.

What should I do if someone has been stung by a jellyfish?

It can be hard to know which species of jellyfish has stung you. If you are in the tropics in Australia and you aren't sure what type of jellyfish it is, treat any sting as if it is a sting by a box jellyfish.

If you are sure the person was stung by a bluebottle jellyfish, and the person is well with a single sting site, treat them as for a non-tropical jellyfish sting.

Get help from a lifeguard if you can.

Tropical areas

Get the person out of the water. Call triple zero (000) and ask for an ambulance if the person has more than one sting site or is unwell.

Start the following first aid:

• If the person is unconscious, perform cardiopulmonary resuscitation (CPR).
• Pour vinegar on the jellyfish stings for 30 seconds. This stops any tentacles (nematocysts) that haven't already fired venom from firing. If vinegar is not available, wash the stings with sea water.
• If vinegar isn't available, carefully remove the tentacles from the skin by flicking them off with a stick, or with your fingers (you may experience minor stinging). It's a good idea to wear gloves if they are available. Rinse the site with seawater.
• Use a cold pack for pain relief after you have treated the sting with vinegar.
• Take the person to hospital as they may need further treatment such as antivenom, strong pain relief or heart monitoring.

Don't let fresh water get onto the sting — this can cause more venom to be released.

Don't rub the sting site.

Non-tropical areas

Get the person out of the water and perform the following first aid:

• Wash the sting site with sea water and remove any tentacles.
• For pain relief, immerse the sting site in hot water for 20 minutes. Make sure the hot water will not burn the person. It should be as hot as they can tolerate — up to 45 degrees Celsius. The person can also have a hot shower.

If it doesn't help, or if there is no hot water, use an ice pack or cold running water instead.

Vinegar should not be used for bluebottle stings — it can cause more venom to be released and may increase the person's pain.

Don't rub the sting site.

Call triple zero (000) and ask for an ambulance if:

• the sting is on the face or neck
• the sting covers a large area
• the person is unwell or having trouble breathing
• the pain doesn't improve

How can I prevent jellyfish stings?

Some things you can do to help prevent jellyfish stings include the following:

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

It's a good idea to swim near a lifeguard who will be able to give you first aid or call an ambulance for you.