Jellyfish in Irish Coastal Waters

Publication Date: Friday 24 Jul 2026

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.

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.

Reduce your risk of getting stung

• Do not touch jellyfish
• Keep away from jellyfish that are washed up on the beach
• Avoid swimming at times when jellyfish appear in large numbers (a jellyfish bloom) or in places known to have many jellyfish. Check for local warning signs before entering the sea
• Wear protective clothing (e.g. wetsuits or rash vests) when swimming or playing in the sea
• 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, the number of stingers released, the amount of poison released, and the person’s general health and sensitivity to the venom.

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

Serious sting reactions require urgent medical attention – call 999 or 112 or attend the Emergency Department

Very rarely a person might have a serious allergic reaction to a sting. These symptoms may include:

• 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.

First aid for milder stings

WHAT TO DO:

• Seek medical attention urgently if you develop any serious symptoms (breathing difficulties, chest pain/tightness, or swelling of the face/throat), if the pain is severe and not relieved by first aid, or if the sting is on or near the eye area
• Remove yourself from the water / Move away from the jellyfish
• Seek help and advice from lifeguards if they are present
• Rinse the affected area with seawater as this can help relieve pain (fresh water can make the pain worse)
• Carefully try to remove any attached tentacles from the skin using tweezers or a towel or gloved hand
• Soak the area in very warm water (as hot as can be tolerated) for around 20-30 minutes. Take care not to burn babies, young children, older adults, or those with poor skin condition. Use heat packs on the area if you are unable to soak it (e.g. if the sting is on your torso)
• Take painkillers such as paracetamol or ibuprofen if needed
• Antihistamine creams or tablets can be taken to reduce itching and redness if necessary
• Keep any puncture wounds clean and dry to avoid them getting infected

WHAT NOT TO DO:

• Do not rub the area – this can result in further venom release
• Do not use fresh water, urine, or alcohol on the sting
• Do not put vinegar on jellyfish stings in Ireland (vinegar is only recommended for tropical jellyfish stings)
• Do not put tight bandages on the sting