What to do if a jellyfish stings you?

What to do if a jellyfish stings you?

Who hasn’t been stung by a jellyfish at least once at sea! Usually the encounter is just unpleasant, but there are also some species that can cause more serious injury. We’ll advise you how to best treat injuries and deal with the more serious stings.

Who hasn’t been stung by a jellyfish at least once at sea! Usually the encounter is just unpleasant, but there are also some species that can cause more serious injury. We’ll advise you how to best treat any injuries.

In more exotic countries where many sailors head in winter, you may encounter the most toxic species of jellyfish, and the consequences of such an encounter may be fatal or long-lasting. Therefore, we have prepared some tips on how to handle serious stings and the subsequent complications.

What happens when you’re stung by a jellyfish and what are the symptoms?

Injuries are caused by jellyfish tentacles which have hundreds of tiny spines with explosive cells (nematocysts) that immediately release poison. Some species have these stinging cells around the perimeter of their bell.


Coming in contact with the poison causes itching, intense burning, tingling, and sometimes severe pain. This causes lesions to the skin, blisters form and a rash or swelling is also common. On top of this you may experience nausea, vomiting and fatigue or malaise. 


Deceptively, the poison of some species has a delayed effect which can be unbeknown to the victim who may think they just scraped themselves somewhere whilst snorkelling. Therefore, it’s best to closely inspect any injury if you’re unsure of the cause.

Stinging tentacles are dangerous and longStinging tentacles are dangerous and long 

An encounter with the most toxic species, can cause a very severe reaction or paralysis of the central nervous system - causing severe pain, breathing problems, difficulty swallowing and, in extremes, respiratory arrest and unconsciousness.

First aid for a jellyfish sting that really works

When you’ve been stung by a jellyfish, reacting quickly is key. It is necessary to prevent the further spread of the toxin, that adheres to the body, as soon as possible.

  • For example, you can try to physically scrape it off with a razor blade or credit card. In an emergency, rub the affected area with sand and try to remove the barbs with tweezers. 
  • Rinse the affected area. Rinse with hot water, as hot as the affected person can withstand (be careful not to scald) or use a warm hair dryer. Rinsing in some type of acid is also effective, ideally something like vinegar. Pouring salt water or alcohol solution over the sting will also help.

Why? The toxin is a protein and must be disrupted or denatured to stop it performing its function, thus stopping it poisoning the affected area. 

Rinsing with vinegar, scraping and hot air are the best when dealing with a stingRinsing with vinegar, scraping and hot air are the best when dealing with a sting 

You can also administer painkillers, antihistamines and locally treat with Fenistil type ointment and disinfectant.

What to watch out for during treatment?

Never rinse the injured area with fresh water. This may release more toxins into the system.


Also beware of the fluid in the blisters. Even if you think that the wound is healing and the worst is behind you, the blisters may burst and “sting” you again. Such an injury can be seen in the following photographs.

Jellyfish (from left) 1. Fresh injury, 2. Secondary fluid blistering, and 3. Condition after a weekJellyfish (from left) 1. Fresh injury, 2. Secondary fluid blistering, and 3. Condition after a week 


In the event of a severe reaction and respiratory arrest, cardiopulmonary resuscitation (CPR) should, of course, be started and the injured should be taken to the doctor as soon as possible.

What kinds of jellyfish do you most often encounter and which to avoid?

We currently know about 300 species of jellyfish. Most live in warm seas, and there are no deadly species living in European waters. However, some are increasingly being found in Mediterranean waters and the Baltic as a result of climate change. Let's take a look at the most famous species together.

1. Harmless species, not just encountered in the Adriatic

  • Moon Jellyfish  (aurelia aurita)

Also known as the common jellyfish or saucer jelly, it’s poison is not dangerous and basically does not sting. This pink beauty with it’s distinctive four-leaf clover can be found in European waters, but also in Egypt. It prefers less salty seas.

Moon Jellyfish (aurelia aurita)Moon Jellyfish (aurelia aurita) 

  • Mediterranean Jellyfish (Cotylorhiza tuberculata)

This common jellyfish, which is nicknamed the fried egg jellyfish is not dangerous and will not harm you in any way. 

Mediterranean Jellyfish (Cotylorhiza tuberculata)Mediterranean Jellyfish (Cotylorhiza tuberculata) 
  • Barrel Jellyfish (Rhizostoma pulmo)

This large jellyfish with its fascinating curled arms occupies warm seas and the Mediterranean. It is also not dangerous and has a very weak sting.  

Barrel Jellyfish (rhizostoma pulmo)Barrel Jellyfish (rhizostoma pulmo) 

2. Dangerous species of jellyfish

  • Mauve Stinger (Pelagia noctiluca)

Its bell is blue-violet with pink tones and has a diameter of about 10 cm. It has four long oral arms with crenulated margins and eight (over a metre long) tentacles that emerge from the umbrella margin. Touching the tentacle of this jellyfish causes instant, sharp pain and blisters in the affected areas heal slowly. A more severe sting will result in nausea and vomiting, weakness, headache and, in rare cases, loss of consciousness.

Mauve Stinger (Pelagia noctiluca)Mauve Stinger (Pelagia noctiluca) 

3. Very dangerous species

  • Portuguese Man O' War (Physalia physalis)

Also known as the "Portuguese man-of-war", it is not a true jellyfish but a siphonophore. It has a beautiful shimmering bladder and incandescent aquamarine shoulders. Its tentacles are about 10 metres long, but sometimes can reach up to 30 metres and it is highly dangerous. Its stings are ten times stronger than jellyfish, using a similar type of poison to the cobra (cobratoxin).


It has no means of propulsion and is driven by winds, currents and tides. Men o’ war live in the warm waters of the Atlantic, the Indian Ocean and the Pacific, and often thousands of them swarm together in a group. In the warm summer months they head north to the poles. They have been observed several times in the Mediterranean recently, including a killing off the coast of Sardinia.  

Portuguese Man OPortuguese Man O 

  • Sea Wasp (Chironex fleckeri)

This jellyfish nicknamed the Sea Wasp has taken many lives on the shores of Australia. Its box-shaped bell measures only a few centimetres, but from each corner grows 15 tentacles that can expand up to ten metres.


On its arms there are quadrilateral "hooks" that stab into the skin. The active substances are cardiotoxins, which cause severe pain, convulsions, breathing difficulties, rapid pressure increase and heart failure. It is even reported that the venom in an adult specimen is enough to kill 60 people.


During the dry season, it lives in the mouth of rivers among mangroves, and during the rainy season from October to May it is washed up on beaches in northern Australia. It also occurs in New Guinea, Thailand, the north of the Philippines and Vietnam.

Čtyřhranka smrtelná (Chironex fleckeri)

  • Irukandji Jellyfish (Carukia Barnesi)

Skin contact with this tiny jellyfish does not seem dangerous at first, but the poison (allegedly a hundred times stronger than the cobra poison), begins to act in about 30 minutes and causes problems called Irukandji syndrome. They manifest themselves as unbearable cramps all over the body, back pain, kidneys, burning, vomiting, increased blood pressure, palpitations and fear of death. Symptoms persist for several tens of hours to days. 

Irukandji Jellyfish (Carukia Barnesi)Irukandji Jellyfish (Carukia Barnesi) 

  • Velella velella

An Interesting jellyfish (in fact, similar to a Portuguese man o' war,  in being a colonial organism) which can glide over the sea surface. It is found mainly off the shores of California, but has also been seen in the Mediterranean. 

Velella velellaVelella velella 

Encountering jellyfish when yachting is not usually dangerous and non-toxic species are stunning in their beauty and elegance. If you take our advice and act quickly when stung, you will usually get only small blisters and a bit of a fright. Yet, of course, caution is always advisable, and if you're heading into an area where poisonous species are present, it is worth looking around. 

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