Ouch! Those Stinging Portuguese Man-of-War

By Jan TenBruggencate

A Portuguese man-of-war. Photo courtesy of NOAA

Everybody’s got a theory on how to treat jellyfish and Portuguese man-of-war stings, but most of those treatments don’t work.

Getting stung is pretty rare in Hawai‘i, but if it happens, it is memorable. I’ve looked down and seen the blue tentacle of the man-of-war slung across my foot, accompanied by what feels like a branding iron pressing onto the skin.

I’ve heard people suggest rubbing a sting site with wet sand, or hot sand, or baking soda, urinating on it, or using vinegar or rubbing alcohol. A poultice of crushed papaya leaves has been suggested. Some suggest using a credit card or razor to scrape the tentacle off.

What actually works? Here’s the short version: full-strength vinegar for starters, and then a long immersion in hot water.

And about those other remedies? Mostly, they cause the stinging cells to discharge more toxin into your flesh. Ouch!

“Alcohols and folk remedies, such as urine, baking soda and shaving cream, caused varying amounts of immediate cnidae (stinger cell) discharge and failed to inhibit further discharge, and thus likely worsen stings.”

That’s from the 2017 paper of an Ireland-Hawai‘i team of researchers who did lab studies on Portuguese man-of-war stings. The Hawaiian part of the team includes Christie L. Wilcox and Angel A. Yanagihara of the University of Hawai‘i. The others are Jasmine L. Headlam and Thomas K. Doyle of National University of Ireland in Galway.

A key point is that as much as that first contact burns, it only represents the firing of a small portion of all the stinging cells that are present.

Two treatment goals are to kill the remaining stinging cells before they fire, then inactivate the venom already injected and stop the pain from increasing.

It turns out the acetic acid in full-strength vinegar — doesn’t matter if it’s rice vinegar, white vinegar or apple cider vinegar — will interfere with the stinging cells’ firing mechanism so they can’t sting you. Citric acid in lemons and limes, or uric acid in urine, they don’t work.

So step one: flood the sting with vinegar.

Next step is to deal with the venom already injected. Yanagihara said that soaking for 45 minutes in water that’s 112-115 degrees Fahrenheit or 45 degrees Celsius will inactivate the venom without burning your skin.

Jan TenBruggencate

Another option, if you’re near a well-stocked store, is the two-step spray and cream kit called StingNoMore®, available at dive shops, some pharmacies, some O‘ahu ABC stores, or through Stingnomore.com. These products, developed in Hawai‘i with funding from the US Department of Defense, will chemically do the job of both the vinegar and hot water, Yanagihara said.

The vinegar-hot water soak treatment works not only for Portuguese man-of-war, but also for the venom from box jellyfish, and other members of the marine family that includes jellies, corals and anemones.

All of these animals have explosive cells containing a nasty cocktail of proteins that constitutes their venom. Vinegar and hot water work for all the ones tested thus far, Yanagihara said.

• Jan TenBruggencate is a Kaua‘i based writer and communications consultant.