Jellyfish stings

Some kinds of jellyfish deliver a painful sting. Find out what to do if you or a family member gets stung.

Photo of a washed up blue bottle, with a pale blue body which looks like you could pop it, and blue tentacles.
Washed-up blue bottle, photo by Pappito at en.wikipedia / CC-BY-SA-3.0.

The Portuguese man-of-war (blue bottle) has a burning sting. It’s not a true jellyfish, which means there are some things you should do differently to treat the sting. These are described below. This is the jellyfish most found in New Zealand waters.

Other jellyfish (rare in New Zealand) include:

  • the lion’s-mane jellyfish, which is a stinging jellyfish. It can be found in colours from white to deep blue. It grows to almost 2 m across. Its tentacles can be up to 5 m long and are almost invisible
  • the mauve stinger, which has only few stinging catch tentacles. It can grow to 40 cm across.
Photo of a lion’s-mane jellyfish, a large, pale blue jellyfish with many tentacles.
Lion’s-mane jellyfish, photo by Jérôme Mallefet / CC BY-NC-SA 3.0.

Call 111 for an ambulance if you or someone else has been stung and has symptoms of a serious allergic reaction or anaphylaxis.

Photo of a mauve stinger, a purple jellyfish with several large tentacles hanging from the bell, and a few thinner catch tentacles.
Mauve stinger, photo by Hans Hillewaert / CC-BY-SA-3.0.

These symptoms include:

  • swelling around the lips and eyes
  • rapid development of a rash
  • shortness of breath or wheezing
  • chest tightness
  • severe dizziness or faints
  • hoarse voice
  • difficulty swallowing or throat tightness
  • signs of shock (pale skin, rapid pulse and fainting).

However, it is rare for a patient to have an anaphylaxis to jellyfish, even if they are stung on the face or neck.

Self care for jellyfish stings

If you or a family member has been stung by a jellyfish, get out of the water and follow these steps.

Vinegar does not help with blue bottle stings.
  • Apply sea water to the area. If you are able to warm up some sea water, pour this over the area (even urine is better than nothing!).
  • Do not apply fresh water as this will activate the stingers.
  • Pull the tentacles off with a dry towel. Wear gloves if you have some, but you can use your fingers – although wash them immediately afterwards.
  • For blue bottle stings, immerse the stung area in water as hot as the person can bear for 20 minutes.
  • Elevate the affected area for 24 hours, and apply ice to decrease the pain.
  • If necessary, take pain relief such as paracetamol.
  • Antihistamines such as Telfast, Claratyne and Phenergan may relieve itching and swelling. A cream with hydrocortisone will reduce inflammation. You can get these from your pharmacy.

Medicine precautions

  1. Do not give aspirin (acetylsalicylic acid) or aspirin-containing products to anyone 18 years or younger because of the risk of a serious illness called Reye's syndrome.
  2. Take non-steroidal anti-inflammatory drugs (NSAIDs) with food or milk to prevent stomach irritation. Do not give NSAIDs to anyone with:
    • NSAID-induced asthma
    • increased risk of bleeding, such as ulcer disease, a bleeding disorder, if taking blood thinners (anticoagulants), or following surgery, significant trauma or major dental work
    • an allergy to NSAIDs.

When to see your doctor

Call your doctor if you have been stung and have:

  • increasing numbness or difficulty breathing
  • signs of poisoning: abdominal pain, muscle cramps, nausea, vomiting
  • signs of infection later: increasing pain, redness, swelling, red streaks leading away from the sting, heat, discharge of pus, fever or chills
  • pain that is not controlled by following the self-care instructions
  • any new or worsening symptoms.

This topic sheet was provided by Healthline.

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