Stings from a Portuguese man o’ war are as common as they are dangerous, yet there’s a lack of consensus over the best way to treat these painful pricks. New research published in the journal Toxins reveals that stings from the man o’ war (Physalia species) shouldn’t be treated any differently than stings from jellyfish, a conclusion that upends conventional wisdom. And no, peeing on yourself is not recommended.


A floating bag of pain in a bag. (Image: Rachel Skubel)

For decades, medical guidelines and folk wisdom suggested an assortment of treatment options, ranging from applications of alcohol and seawater through to shaving cream, urine, and baking soda. New research from the University of Hawaii at Manoa (UHM) and the National University of Ireland (NUI) Galway now shows that most of these ideas are complete bunk—if not counterproductive—and that the best approach is to apply a bit of vinegar and some warmth.


These siphonophores (technically not a jellyfish), which are distinct for their bright blue tentacles and colorful, inflated floating sails, often wash ashore, threatening unsuspecting couples who enjoy long walks on the beach. The poisonous landmines sting hundreds of people each day around the world.



When a man o’ war stings, its long tentacles release thousands of microscopic venom-injecting capsules called nematocysts. On contact with skin, the nematocysts deliver a toxic chemical cocktail into its victim. The effects of this venom can range from mild to life threatening, but typically include immediate pain that can last upwards of 15 to 20 minutes. In more severe cases, a sting can trigger chest pain, difficulty breathing, and even death.

Frustrated by the lack of scientific consensus on how to deal with a man o’war sting, a research team led by Christie Wilcox from UHM’s Pacific Cnidaria Research Laboratory (PCRL) put their heads together.


“Without solid science to back up medical practices, we have ended up with conflicting official recommendations around the world, leading to confusion and, in many cases, practices that actually worsen stings or even cost lives,” said PCRL scientist and study co-author Angel Yanagihara in a statement.

Using a set of experimental assays developed by Yanagihara, the researchers were able to quantify the stinging and venom activity of man o’ wars in real time. The scientists tested a variety of rinse solutions on both Atlantic and Pacific Physalia species, analyzing the ability of these solutions to inhibit the discharge of toxins following a sting.


Their experiments showed that the best way to treat a sting from a man o’ war is to rinse the wound with vinegar to remove any residual stingers or bits of tentacle left on the skin, and then immerse the wound in hot water—ideally at a temperature of 113 degrees F (45 degrees C)—for 45 minutes. A hot pack will substitute nicely for the hot water, as will a spray called Sting No More, which was developed to treat combat divers under a Department of Defense grant. Even a quick, 30-second wash of diluted vinegar will confer protective effects.

“Since vinegar is already the go-to rinse solution for other jellyfish stings, removing the Physalia caveat will simplify treatment recommendations making them easier for the general public and first responders to remember and apply correctly,” conclude the authors in their study.


As for other treatments, such as alcohol, urine, baking soda, dish soap, lemon juice, regular cola, and seawater, they “caused varying amounts of immediate cnidae discharge and failed to inhibit further discharge, and thus likely worsen stings.” The application of seawater—a fairly common prescription—was particularly bad, spreading the stinging capsules over more skin area, making it much worse.

“Given that most recommendations expressly forbid the use of vinegar and recommend seawater rinses, these findings completely upend current protocols,” said Yanagihara.


The ability of vinegar to suppress the discharge of cnidaria toxin after a sting is likely the result of its pH, or acidic content. But other acidic solutions didn’t confer the same protective effects, and the researchers aren’t entirely sure why. As they investigate further, just remember to pack a bottle of vinegar and a hot pack for that next trip to your favorite tropical paradise.

Correction: A previous version of this post misidentified man o’ wars as jellyfish. Man o’ wars are siphonophores, which unlike jellyfish, are comprised of highly specialized individual animals called zooids. Gizmodo regrets the error.


[Toxins]