Jellyfish swarms descend on Côte d'Azur

Stricken bathers from Cannes to Antibes, incuding Villeneuve-Loubet and Cagnes-sur-mer, have been treated for painful burns caused by their stingers.

Monaco and Nice have so far been spared, although experts say much of the coast could be hit this year given the size of shoals observed.

In one case a rescue operation had to be mounted to save a group of youths whose raft was surrounded by the poisonous jellyfish.

Biologists say the onslaught of Pelagia noctiluca – commonly known as the mauve stinger - is in part down to climate change and rising water temperatures, but also a decline in its only real predators – turtles and tuna.

The species, which glows in the dark, has also benefited from rising plankton levels and pollution-related nutrients.

Its eight tentacles can reach two metres long and contact with them causes burns which can provoke asthma and allergic attacks, and in rare cases heart failure.

Cannes and Monaco have installed floating barriers to keep the pests at bay, whereas Antibes has a jellyfish-vacuum boat, which sucks up the stingers in vast quantities.

Stay Safe! As always, safety is the most important step. Jellyfish tentacles (nematocysts) may still be on the skin. Follow universal precautions and wear personal protective equipment if available.

Rinse the tentacles off with salt water. Do not use fresh water, it will worsen the stinging pain.

Remove any remaining tentacles with a gloved hand or tweezers.

Watch for anaphylaxis (severe allergic reaction).

Use vinegar (acetic acid) to neutralize the toxin in the nematocysts. In some cases, the use of vinegar is controversial (see tips below).

Restrict movement of the affected area to discourage envenomation.

Ibuprofen and acetaminophen will help relieve pain. Ice or heat may also help. Mild itching may be helped with diphenhydramine.