How Do You Treat a Jellyfish Sting?

Start by getting the tentacles off without spreading venom. NOAA advises looking for any tentacle stuck to the skin and flushing the area well with cold ocean water, not rubbing the sting area because that could spread venom further into the body, and then applying vinegar or an evidence-based commercial product if pain continues. Virgin Islands National Park says tentacles must be removed from the skin or they will continue to fire, and that bare hands should not be used to remove them.

Vinegar depends on the animal. Padre Island National Seashore advises rinsing with seawater, testing a small area with vinegar and soaking for at least 30 minutes if it helps, and immersing the injury in hot water if vinegar increases the discharge of stinging cells. Gulf Islands National Seashore says vinegar should only be used if you are positive you were not stung by a Portuguese man-of-war, citing studies suggesting vinegar can make a man-of-war sting worse, and advises applying heat as warm as the person can tolerate after removing any remaining tentacles.

Research is refining the advice. A 2025 study of box jellyfish stings in Military Medicine found that vinegar dousing of the sting site followed by a 42 to 45 degree Celsius hot pack for 45 minutes also irreversibly inhibited venom activity, though to a lesser extent, while saltwater rinse and ice packs were totally ineffective and led to more tissue damage than the untreated sting.

Know when it is serious. Virgin Islands National Park says jellyfish stings can range from mild stinging, itching and redness to severe allergic reaction and anaphylactic shock, and Gulf Islands says pain usually subsides after a few hours but to seek immediate medical attention for any sign of allergic reaction. NOAA says a Portuguese man o' war sting is rarely deadly but painful, and that a man o' war may still sting weeks after washing ashore, while a few of the roughly 50 box jellyfish species have venom that can cause paralysis, cardiac arrest and death within minutes.