Jellyfish in Irish Coastal Waters

Warm tropical waters are the most likely place to find dangerous jellyfish. Luckily Irish waters are not home to the most dangerous jellyfish known, the Box jellyfish, which is common in Australia. Jellyfish stings in Ireland are not usually life threatening and most just require basic first aid  (see below) and simple pain relief.

There are five native jellyfish species in Ireland:

  • Barrel
  • Blue
  • Common (Moon)
  • Compass
  • Lion’s Mane

A sixth type (Pelagia noctiluca) occasionally makes an appearance in Irish coastal waters. There have been rare reported sightings of the Portuguese Man O’War in Irish waters. The Portuguese Man O’War is not a true jellyfish but is closely related to the jellyfish family and can give a bad sting. The Lion’s Mane is the most serious jellyfish in Irish waters.

Click here to view the Jellyfish ID Card.

Jellyfish usually remain in their preferred habitats, for example:

  • Barrel jellyfish - can form enormous blooms every year off Rosslare and Wexford Harbours, yet is rarely found anywhere else in such large numbers.
  • Blue jellyfish – found in highest numbers off the south and west coasts, and at times can be found throughout the entire Celtic Sea.
  • Common jellyfish - this is the most widespread jellyfish and is most often found in harbours and estuaries.  It can sometimes form very dense blooms.
  • Compass jellyfish - found in highest numbers off the south and west coasts, and at times can be found throughout the entire Celtic Sea.
  • Lion’s Mane jellyfish - prefers the cooler waters of the Irish Sea and especially the waters off Dublin.  Recently an increase has been seen in waters off the East Coast and some very large jellyfish have been observed on beaches in this area.

Jellyfish stings

All jellyfish possess stinging cells, “stingers”, on their tentacles.  Brushing against tentacles can cause the release of these stingers which contain venom (poison).  Depending on the type of jellyfish, the stingers may not be sharp enough and long enough to pierce the skin and the skin forms a natural barrier to most stings.  More delicate areas, such as the eyes and lips, might be more easily pierced.

However, the Lion’s Mane stinging cells are much sharper and can pierce skin easily resulting in a painful sting. Jellyfish stings in Ireland are not usually life threatening and just require basic first aid (see below) and simple pain relief.

Risk of getting stung

Your risk of getting stung is increased if you:

  • touch jellyfish, so make sure curious children don’t get too close
  • swim at times when jellyfish appear in large numbers (a jellyfish bloom)
  • swim in a place known to have many jellyfish, especially on a downwind shore
  • swim or dive in jellyfish areas without protective clothing
  • play or sunbathe where jellyfish are washed up on the beach

Animals are also at risk of getting stung, therefore keep your dog on a lead when walking on the beach.

Symptoms of a jellyfish sting

Symptoms depend on the:

  • type of jellyfish
  • size of the sting
  • number of stingers released
  • amount of poison released
  • person's own sensitivity to the venom 
  • person's general health status

Most symptoms will be mild and local to the sting area such as:

  • immediate stinging pain at the site of the sting
  • skin reactions such as redness and itching which can start immediately after being stung or sometime after the sting

More severe symptoms can include:

  • severe pain
  • long lasting pain
  • swelling of the affected area
  • significant and long lasting skin reactions


Serious sting reactions which require urgent medical attention

  • Very rarely a person might have a serious allergic reaction to a sting – breathing difficulties, chest tightness, swelling of the lips, mouth or tongue
  • Serious generalised reactions to a jellyfish sting are more common in countries with highly poisonous jellyfish, such as the Box jellyfish
  • A sting from a Lion’s Mane jellyfish can cause nausea, sweating, cramps, headaches and other symptoms
  • A sting from a Pelagia noctiluca (only occasionally found in Irish waters) can cause dizziness, vomiting, diarrhoea, difficulty breathing and other symptoms
  • A sting from the Portuguese Man O’War (rarely seen in Irish waters) can cause symptoms such as muscle spasms, headaches, diarrhoea, difficulty breathing, heart rhythm problems and other symptoms
  • If in doubt seek medical attention

What to do if you have been stung

  • Remove yourself from the water / vicinity of the jellyfish
  • If helping someone else make sure you don’t get stung yourself
  • Seek help and advice from lifeguards if you are on a lifeguarded beach
  • Try to carefully remove any attached tentacles by
            • flushing the sting area with sea water
            • removing tentacles with gloved hands, clean stick, tweezers, or scraping gently with the edge of a credit card. Don’t try to rub them off.
  • Mild symptoms of pain and swelling can be treated with simple painkillers such as paracetamol and ibuprofen
  • Mild itching at the sting site may respond to anti-histamine creams
  • Apply a 'dry cold pack' to the area (i.e. place a cold pack or ice inside a plastic bag and then wrap this package in a t-shirt or other piece of cloth)
  • Use HOT WATER for Portuguese Man O'War stings at approximately 45° Celsius for 20 minutes
  • Keep any puncture wounds clean and dry to avoid them getting infected
  • Seek medical attention if you develop any serious symptoms

What not to do

  • Don’t rub the area
  • Don’t rinse with fresh water. Use sea water
  • Don’t urinate (pee) on the sting
  • Don’t use vinegar for the types of jellyfish stings that might happen in Ireland
  • Don’t use alcohol
  • Don’t put on a tight bandage