Jellyfish stings; what you need to know

Summer is around the corner and the sea is inviting. But be careful, as danger may lie just out of sight. Jellyfish are exotic and beautiful curiosities that carry an ingenious defence mechanism. They also carry a rather painful sting. This article delves below the surface and tells you a little about these fascinating creatures and what to do in the case of a bad encounter. To preface this article, I can tell you it's nothing to do with urine.

Jellyfish are complex creatures with an amorphous head, ribbon-like tentacles and a vicious sting. They are one of the few animals on the planet without bones, and have been around for up to 700 million years. One species may even be immortal. They are found all over the world, from the sea to freshwater lakes, and come in many varieties. They owe their survival to their exotic evolution and dramatic defences. They are to be respected by us relatively short-lived, bony and hairy creatures.

British jellyfish stings are not commonly deadly. A 'sting' leaves cells in the skin which will secrete a class of proteins called 'porins'. These act like a toxin. Usually the sting will cause localised pain and blistering which may persist. Rarer side effects include nausea, vomiting, tummy pain, numbness, tingling or diarrhoea. In severe cases where someone may be allergic to a toxin, chest pain, shortness of breath or worse may occur. These are the cases to really worry about. Multiple stings pose more of a risk.

Mild symptoms can be treated easily. Simply using tweezers to remove any leftover tentacle, and by using an ice pack on the area, you can limit the severity and duration of pain. The trick is to remove any leftover cells which leak toxin. Using simple analgesia, such asparacetamol or ibuprofen will usually settle pain. If the area continues to hurt, itch or swell, this may indicate infection or allergy and requires seeing a doctor if you feel concerned. Oral antihistamines may help. Vinegar, baking soda and bodily fluids will not. All will agitate the leftover cells to secrete more toxin, and the latter will ruin friendships.

The main concern is whether someone is having a severe allergic reaction. If it is a large sting, a sting on the face or genitals, in an elderly or very young patient, or if someone complains of chest pain, shortness of breath or seems unwell, you must seek emergency help. In these cases, the severe reaction could lead to shock and even to death. These events are very rare, but like an allergy to bee sting, can be fatal. If you are unsure, call 999. Always best to be safe.

Away from UK shores

More exotic species found abroad may be a different story. Australian 'box' and 'Irukandji' jellyfish are especially deadly and much more likely to attack in greater numbers and cause severe reactions. The sting causes a chain reaction in the body which can lead to shock and death. In this case the key message is to get to an emergency department who may use medications and other treatments. In the meantime, get out of the water, pull out the tentacles and use ice packs. The safest method is to avoid stings in the first place.

The simplest plan is to avoid the water. If you have decided to enter the lair of the pointy-toothed dinosaurs and stingy balloons, then education and preparation are important. Observe guidance and ask around, are jellyfish common locally? Protective shoes, wetsuits and lotions may go a long way to helping you avoid, or weaken, any sting. Do not play with jellyfish in the sea or if on shore, leave the water and tell a lifeguard. Like any bite, sting or other healthcare problem, prevention is the best cure.

Enjoy the water.


Ben is a young NHS doctor in the Southwest. His interests include neurology, health communication, and medical ethics. He is also an avid advocate of compassionate care and quality improvement, running a project in the Southwest around medical humanities.

The opinions expressed in this article are the author's alone. Where facts are presented, these are evidence-based. The author is happy to receive questions. There are no conflicts of interest.

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