A guide to jellyfish - and what you need to do (and not do!) if you get stung

We might be feeling a little hard done by weatherwise this summer, but it hasn’t stopped the influx of jellyfish to Donegal’s beaches, albeit a little later than usual.

The last few weeks have seen a big increase in the number of jellyfish spotted on beaches and in the water, with several large blooms reported at various beaches along the Donegal coast. 

The fear of getting stung by a jellyfish is so strong for some people that they forfeit the pleasure of a refreshing dip to help cool off on a hot summer day. And unfortunately, the warmer the weather, the higher the likelihood of a jellyfish bloom.

However, it is helpful to remember that not all jellyfish sting, and those that cause the most severe harm are not found in Irish waters.

According to the HSE, most stings require no more than basic first aid and simple pain relief.

So what species of jellyfish can beach goers and sea swimmers expect to encounter in Donegal, and which ones sting?

Common or Moon Jellyfish

The Common (also known as Moon) jellyfish is the one most often seen at our beaches. They are often only a few inches in diameter and can be identified by their four purple/pink rings. While it can be daunting to encounter a large jellyfish bloom (a lot of them together) while bathing, the small moon jellyfish with no tentacles do not sting. This is because jellyfish stingers are only found on the tentacles. 

Larger Common jellyfish develop tentacles and these can deliver a mild sting, but on the whole, they are relatively harmless.

Compass Jellyfish

Another jellyfish often encountered in Donegal  is the Compass. It has brown lines which meet to form v-shapes at the centre of the dome. 

It can grow up to 50cm or 20 inches in diameter and with 24 tentacles and four frilly mouth-arms, it can sting. It is relatively easy to spot in clear water, but blends in where there is a lot of seaweed.

Barrel Jellyfish

Barrel jellyfish are found in big numbers off Ireland’s south east coast but are only rarely seen in Donegal. Rather than tentacles, they have eight mouth arms. As a result, they do not sting  but can cause an allergic reaction.

Blue Jellyfish

The Blue jellyfish has a translucent body with blue or purple rings. It too is found off the west coast and has been sighted in recent years on Donegal beaches. With masses of tentacles, it can deliver a sting.

Lion's Mane

The very mention of the Lion’s Mane jellyfish, or the photos which appear from time to time on social media are enough to strike terror into many people with even a mild fear of jellyfish.

This is not without reason. 

According to the HSE: “The Lion’s Mane stinging cells are much sharper and can pierce skin easily resulting in a painful sting.”

“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.”

The good news for those of us here in Donegal is that while there have been occasional sightings on the western seaboard, such occurrences are quite rare. 

Portuguese Man O’War o’war and By-the-wind Sailors

There are occasional sightings of the Portuguese man o’war or by-the-wind sailors on Donegal beaches. Neither species is a true jellyfish but both are close relations.

The Portuguese man o’war tentacles contain stinging nematocysts. These are microscopic capsules loaded with coiled, barbed tubes that deliver venom capable of paralysing and killing small fish and crustaceans. Its sting is rarely deadly to people but it can be very painful and can cause welts if there is direct contact with skin.

By-the-wind sailors have a very mild sting that allows them to gather plankton. It is extremely mild to humans, however people are advised not to touch by-the-wind sailors as there is a risk of skin or eye irritation.

Treating a Sting

If there is a lifeguard on duty, that is the first port of call for any kind of first aid at a beach, including jellyfish stings. 

Tentacles that are attached to the skin should be removed with gloved hands, tweezers or by scraping with the edge of a plastic card such as a bank card. They should never be rubbed off. 

Mild pain can be treated with over-the-counter painkillers and itching may be eased by antihistamine creams. 

A dry cold pack will give relief for most stings, though for a Portuguese man o’war sting, warm water of 45°C should be applied for 20 minutes.

Anyone who gets anything other than mild symptoms should seek medical advice. 

Myths

There are a number of myths regarding the treatment of jellyfish stings.

According to the HSE: 

-Don’t urinate on the sting.

-Don’t rinse with fresh water. Use seawater.

-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.”

Protection

Wearing protective clothing such as a wetsuit reduces the likelihood of a jellyfish sting. People are also advised to avoid standing on jellyfish stranded on beaches, and to be aware of the risk to dogs while out walking on the shore.

A section on the HSE website www.hse.ie/eng/health/hl/water/bathing/jellyfish-in-irish-coastal-waters.html contains more information including a link to a jellyfish identification card.