In case it stings you

How to avoid jellyfish?

Watch the sea: if they are present, they are usually visible and the only way to avoid them is... not to enter in the water. Jellyfish do not attak us, they do not come towards us: it is us who go towards them. Jellyfish can swim vertically, and they can stay near the surface and then sink to the bottom. They move, and usually go where the currents bring them. There are no definite rules: they can be anywhere. Because the jellyfish are part of plankton and they move with the currents. They can swim but they cannot travel against the currents. 

If there is a jellyfish in the distance, is it safe to swim? 

If there are stinging jellyfish in the sea, it is better not to go in the water, unless they are really very very few. The jellyfish that sting usually do have very long tentacles: those of Pelagia can reach 10 m, those of Physalia 20-30 m. Even if they are far, it is possible that their tentacles are much nearer.

Can jellyfish kill people? 

Yes, some can inject deadly venoms, others can cause anaphylactic shocks. Furthermore, the strong pain that some stings cause can be fatal in weak individuals, with heart problems. It is better to go to the hospital if there are widespread skin reactions, heavy sweating, pale coloration, and lack of orientation. In Australia jellyfish kill more people than sharks. But this is not the case in the Mediterranean, where just one case of deadly sting (by Physalia) has been recorded so far.

Can we touch the gelatinous plankters that do not sting? 

Better not. Real jellyfish, with cnidocysts, can have harmless stinging cells (for us) and we can touch them with no problem, but the stinging cells can remain on the palm of the hand and if we then touch the eyes, or other delicate parts of our body, we can transfer the venom and cause some inflammation.

What is the composition of jellyfish venoms? 

It is made by a mixture of three proteins, one has paralyzing effects, the other  causes inflammation and the third is neurotoxic. There are no specific antidotes for these venoms, but they are quickly degraded at high temperatures.

How does it feel to be stung?

A local inflammation causes a burning and painful feeling. The skin becomes read and bubbles appear, but after some minutes the burning sensation ends and just a hitch remains. Pain and burning vary depending on where the sting occurred and can be unbearable if more than 50% of the body surface is affected.

What to do, if stung? 

Remain calm, breath normally, get out the water immediately and wash the stung part with sea water. Do not use fresh water because this favors the discharge of the stinging cells. Sea water, instead, helps removing tentacle pieces that might have remained still attached to the skin, and which retain their stinging properties even when detached from the jellyfish.

Natural remedies: do they work? Is it true that a warm body can disactivate the venom? What about urine, vinegar or alcohol?

The temperature of a stone should be higher than 40 °C to be effective. Urine and other liquids do not serve the purpose, and might even worsen the inflammation.

What is an effective medication? 

There are several products that can be bought in a pharmacy, and it is better to have them when at sea.

How to avoid the formation of scars? 

Do not expose the stung part to the sun, but keep it in the shade until the inflammation is over, and this might require also two weeks.

What about anti-jellyfish creams? 

They have been developed by imitating the avoidance system of the clownfish, a symbiont of cnidarians that is not stung. These creams make the skin slippery and so make it difficult for the tentacles to adhere to it, mimicking the recognition system of the jellyfish (the tentacles do not sting each other when they get in touch).

Is it true that jellyfish love clean and warm seas? 

They can live anywhere, depending on the species, from the poles to the equator, from surface to very deep waters. Global warming is favoring the spread of tropical species.

Is there a season for the jellyfish? 

Usually they start to be present at the beginning of the spring, when the phytoplankton blooms and sustains the subsequent bloom of zooplankton, the food of many jellyfish. Velella is especially abundant in the spring, whereas Pelagia is a typical summer species, just as most of the others. Global warming, however, is widening the time window in which these species are present.