The best noncommercial therapy for man-of-war stings is to douse them with vinegar and apply heat, the same conclusion reached in a recent study of box jellyfish stings, University of Hawaii researchers have found.

Other first-aid remedies touted on the internet do more harm than good — including applying seawater, ice packs, shaving cream, alcohol and even the popular folk myth of urine, according to the researchers’ latest study in the journal Toxins.

Christie Wilcox, a postdoctoral fellow at the University of Hawaii John A. Burns School of Medicine, and Angel Yanagihara, head of the Pacific Cnidaria Research Laboratory at UH Manoa, published their results in an online article, “Assessing the Efficacy of First-Aid Measures in Physalia,” on April 26. Cnidaria is the phylum that contains jellyfish, men-of-war and anemones.

Men-of-war, also known as bluebottles or Physalia utriculus, drift in island waters and wash up on beaches with their distinctive bubble floats and long tentacles. They are not true jellyfish, and are more common than the more deadly box jellies. Men-of-war deliver a painful sting which can be dangerous to the sensitive.

“Like box jellies, the best noncommercial first aid that you can use for man-of-war stings is to rinse with vinegar for 30 seconds, which will inactivate the stinging cells so that you don’t get stung worse, and then apply heat,” said Wilcox, the lead author. “It’s a two-step protocol.”

“Everyone always asks whether you can pee on it, but no, no, do not pee on it,” she said, adding that she was horrified to see in the experiments that urine caused “massive discharge of stinging cells.”

Scraping a sting site with a credit card is even worse, she said. Some people use that method to remove the large stinger left by a bee. But it does not work with the tiny stinging cell capsules of man-of-war tentacles, and instead causes them to fire more venom, she said.

“Scraping is basically the worst thing you can do,” she said. “Pressure is one of the ways to eject venom. It’s a great way to get stinging cells to discharge.”

Wilcox added, “The idea that you’re scraping off tentacles isn’t really true. They anchor themselves into these tiny microscopic tubules. They act like tiny hypodermic needles, except they stick in you, like hypodermic needles covered in spines.”

The researchers collaborated with a colleague in Ireland, Tom Doyle of the National University of Ireland Galway, to test the larger Atlantic man-of-war, or Physalia physalis. The results aligned perfectly.

Vinegar should be applied at full strength, not diluted, for 30 seconds, followed by a hot pack or immersion in hot water (113 degrees Fahrenheit or 45 degrees Celsius) for 45 minutes, the scientists found. Heat inactivates the already-injected venom. Those are the same recommendations reached in Yanagihara and Wilcox’s previous study of box jellies, published March 15 in Toxins.

A commercial product, Sting No More spray, developed by Yanagihara under a Defense Department contract, worked best in both studies.

In their experiments the researchers applied fresh man-of-war tentacles to a blood agarose model that mimics human tissue, then assessed sting activity and venom load under different scenarios.

“It’s a direct measure of venom activity, whereas things like pain are subjective,” Wilcox said.

“Part of why we wanted to conduct this research is that everyone’s got an opinion,” she added. “When it comes to medicine, we should have facts. We don’t want random ideas. We want evidence-based medicine.”