The presence of Portuguese man o' war, marine organisms with venomous, tentacles, has increased this summer in northern Spain, especially in Cantabria and the Basque Country, where the authorities have had to restrict swimming and temporarily close several beaches after recording more than a hundred stings in a single day.

According to San Sebastián city council, most of the treatments were for minor injuries and the number of incidents was low compared with the number of beachgoers.

The Portuguese man o' war (Physalia physalis) is often mistaken for a jellyfish, although it is in fact a colonial organism. Its long tentacles contain stinging cells capable of causing intense pain and, in some cases, serious reactions, so the authorities advise avoiding any contact, even when the animal appears dead or washed up on the sand.

What to do if you are stung

The Basque Government's Department of Health recommends (source in Spanish) leaving the water immediately and going to the lifeguard post or seeking medical care if severe symptoms appear.