There's a lot of folklore on how to treat a jellyfish sting, but the science suggests your best bets may be hot water and topical painkillers – at least in North American waters.
Jellyfish stings are usually not dangerous, but they are very painful. The popularly promoted antidotes range from vinegar to meat tenderizer to baking soda mixed with water. In a pinch, you, or a very good friend, might try peeing on the sting.
Right now, the American Heart Association and American Red Cross recommend vinegar or baking soda "slurry," followed by heat or ice, as the best fixes.
But that's based mainly on studies done in Australia and Indonesia, said Dr Nicholas T. Ward of the University of California, San Diego.
Jellyfish not common in North America
And the jellyfish species there are not commonly found in North American waters, Ward said. So he and his colleagues combed the medical literature for studies specific to North American and Hawaiian jellyfish. They found 19.
Based on those studies, it seems the most broadly effective remedies are simple hot water and creams containing the pain-numbing medication lidocaine.
"The principle behind the use of lidocaine is that it acts as a local anaesthetic (and) appears to inhibit the further discharge of nematocysts remaining on the skin," Ward explained.
Nematocysts are the "venom sacs" jellyfish leave behind as a further insult after they sting. It's important to get those sacs off of the skin, Ward said, because they can continue to release venom.
Handle venom sacs with care
Simple hot water may help by "denaturing" and inactivating the venom, according to Ward.
Of course, you might not have a tube of lidocaine in your beach bag when a jellyfish strikes. Hot water, too, may be hard to find.
In that case, removing the venom sacs from your skin and washing the area with saltwater might help.
But handle those venom sacs with care, Ward advised.
He suggested using the edge of a credit card, or something similar, to scrape the sacs from the skin.
"The idea is to avoid crushing the sac and spreading venom, which wiping with a towel could do," Ward said.
Vinegar may worse pain
Jellyfish also often leave behind a tentacle or two that need to be removed. Ward said it's best not to use your bare hand.
According to the researchers, there's no scientific evidence to suggest urine or meat tenderizer help to noticeably relieve the pain of jellyfish stings.
Even in North American waters, though, there is some variation in which remedies are effective, Ward's team reports in the Annals of Emergency Medicine.
Specifically, vinegar seems to take the bite out of injuries inflicted by species known as bluebottles, or Portuguese man-of-wars. In North America, those jellyfish are mainly found off the coast of Florida and in the Gulf of Mexico.
However, Ward said, with stings from most species native to North America and Hawaii, vinegar may actually worsen your pain and cause any remaining venom sacs to discharge.
(Amy Norton, Reuters Health, June 2012)