How does a jellyfish sting?

In case of jelly fish attack: Is a Vinegar emergency wash helpful?

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You’re swimming in the ocean when something brushes your leg. When the tingling sets in, you realize you’ve been stung by a jellyfish. How do these beautiful gelatinous creatures pack such a painful punch? Neosha S Kashef details the science behind the sting.

People often recommend different remedies on how to treat jellyfish stings, but advice may be conflicting. Some say you should apply vinegar, alcohol, ammonia, meat tenderisers and baking powder, rinse the sting with fresh water or even urine. Others disagree, saying that some of these will make the sting worse. A quick search on the internet does not help clarify matters at all.

According to biology professor Patrick J. Schembri, “there is no sure remedy for jellyfish stings that will work on all people at all times, and what works on one occasion may make matters worse on another”. It doesn’t stop getting complicated.

“Understanding this entails looking at the way jellyfish sting,” he said.

Stinging cells, called cnidocytes, are used by jellyfish for feeding and defence against predators. One tentacle may have hundreds of thousands of such cells. Each cells nematocysts, which are capsules, containing venom.

Tentacles can become detached from jellyfish but still sting. “This is the reason why mechanical means of removing jellyfish en masse from the water, such as by the use of nets, do not make the water safe to swim in,” he said.

“The nematocyst acts like a combined harpoon and hypodermic syringe, attaching the prey to the tentacle and at the same time subduing or killing it by injecting a powerful cocktail of toxins. In the case of a human brushing against a jellyfish tentacle, the ‘harpoons’ embed themselves in the skin, injecting their contents and causing the stinging sensation,” Prof. Schembri explained.

Remedies are therefore intended to remove the fragments of tentacle that remain stuck to the skin and to prevent undischarged nematocysts from releasing more painful toxins.

Since their release is affected by the acidity or alkalinity of water, its chemical composition, chemicals released into the water by prey or any object that touches the jellyfish, and depending on how hungry the jellyfish is, white vinegar prevents further venom from penetrating. Meat tenderiser, or sodium bicarbonate (baking soda) will neutralise any nematocysts that have not yet discharged into the skin.

Prof. Schembri said the effectiveness of remedies depends on the person affected. “For example, which part of the body was stung, what chemicals (sun tan oil, cosmetics etc.) were applied to the area before the stinging occurred and how vigorously the affected area was rubbed before the remedy was applied, among others”.

Treating stings

Wash off tentacles with fresh water
The instinctive reaction of pulling back often rips off the tentacles of the jellyfish which remain stuck to the body, even if they are practically invisible. Washing them off with a stream of fresh water is useful, though gently applying water to them may cause nematocysts to fire releasing more poison.

Some recommend applying shaving cream to the affected area and removing any remaining nematocysts with a knife edge, safety razor, or credit card.

Do not rub a sting
Rubbing causes inactive nematocysts on the body, or stinging cells, to activate, increasing the release of toxins and the pain.

Avoid use of sea water
Sea water should only be used as a last resort since it may only include fragmented tentacles and introduce bacteria or viruses.

Jellyfish (and chicken) salad!

Disgusting as it might sound to westerners, especially those nursing a sting, jellyfish feature in a Chinese salad along with shredded chicken and sesame seeds. A recipe book called The Food Of China by Deh-Ta Hsiung and Nina Simonds warns that jellyfish are only ever eaten once they have been preserved and dried. “They have a crunchy texture and are not like jelly,” it says, going on to list the ingredients and describe how the dish may be prepared.

http://www.timesofmalta.com/articles/view/20060819/local/waiting-for-the-sting.44115