In some cases the sting can cause an allergic reaction and in rare cases, heart failure or even death. A man picks up a Portuguese man o' war or bluebottle, on Ondarreta beach in the Spanish Basque city of San Sebastián on August 6, 2026. 1: Don't touch itMan-of-war fish have stinging cells that are still active and capable of stinging even after the creature is dead and washed up on shore. So don't touch it. 3: Get help if you are stungIf you are stung then leave the water immediately and look for a lifeguard.