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The jellyfish is a marine animal belonging to the Phylum of the Cnidarians, (or Coelenterates).

The body of the jellyfish is mainly composed of water (98%).

Its generic shape resembles an umbrella with long tentacles, with the purpose of defense and predation.

In the Mediterranean Sea, jellyfish are present in abundance. You can therefore incur in their "sting" when swimming or diving.

Jellyfish are marine animals that move vertically, so they are found on the surface and can sink to the bottom. Often, these are carried away by currents, whose motion they are unable to counter .  The jellyfish do not attack humans spontaneously, nor do they purposely go towards swimmers and fishermen; rather, it is the swimmers who get too close to the animal and bump it involuntarily.

It should be clarified that the jellyfish does not sting, since it does not have a real sting.  In fact, it is a stinging animal: when the jellyfish is inadvertently touched, the tentacles rest on the skin of the human victim and they release highly irritating substances that produce a skin reaction, similar to a first or second degree chemical burn .

The "poison" that causes the typical manifestations of the jellyfish sting is made up of a mixture of three proteins with a synergistic effect:

•     Ipnotoxina: it is responsible for an anesthetic action, therefore paralyzing the potential prey;

•     Talaxin: after the contact between the tentacles and the skin, it is the inflammatory response in man; in people susceptible from an immune point of view, thalassin can be allergenic;

•     Congestine: it produces a paralysis of the circulatory and respiratory system resulting in lethal death.

In most cases, the jellyfish sting causes pain, erythema , itching , and swelling. Responsible for this reaction are the tentacles of the marine animal, in which there are cnidocysts (also known as nematocysts or nematoid cysts), that is, small cellular organelles that contain the stinging substance. The latter is constituted, as anticipated, by a mixture of three proteins, with an inflammatory and neurotoxic effect. The toxins contained in the cnidocysts are used by the jellyfish to defend itself and paralyze a potential prey.

When the marine animal collides with a part of the body, the tentacles lean like a sucker. The cnidocysts are thus deposited on the victim's skin and their rupture releases the poison. The latter is thermolabile, that is, it degrades at high temperatures (over 50 degrees centigrade, like the boiling water of tea you take at the bar).

In susceptible people, the jellyfish sting can trigger anaphylactic shock, compromising vital functions in a short time, up to death.

In the Mediterranean Sea, less stinging jellyfish are observed more frequently, such as, for example, the Sea lung (Rhizostoma pulmo) or the Mediterranean Cassiopeia (Cotylorhiza tuberculata). In some periods of the year, close to the Italian coasts, however, it is possible to come across the luminous jellyfish (Pelagia noctiluca), capable of very painful stings.

At the first contact between skin and jellyfish, there is a strong burning sensation. Soon after, the affected skin surface turns red and small wheals (swellings of the skin) appear, similar to those of hives . The pain associated with this irritation begins to subside after about twenty minutes, leaving room for intense itching.

Possible complications

If after the jellyfish sting, the skin reaction becomes very extensive and is associated with difficulty breathing , mental confusion , profuse sweating, pallor and disorientation, it is good to go urgently to the emergency room. The jellyfish sting can cause, in fact, anaphylactic shock and these manifestations can represent an alarm bell.

Some jellyfish are almost harmless to humans: in any case, it is good to avoid touching them. Their stinging liquid can remain on the hands , which can easily transfer it to the mouth, eyes or other delicate parts of the body, where it can still cause an inflammatory reaction.