Popular home remedies and even some authoritative advice on how to treat a jellyfish sting can make the sting worse, according to a recently published study by the University of Hawai‘i at Mānoa (UHM).

UHM researchers investigated whether commonly recommended first aid actions such as rinsing with seawater or scraping away tentacles lessen the severity of stings from two dangerous box jellyfish species. Their results, published this week in the journal Toxins, reveal that some of the most commonly recommended practices actually worsen stings.

“Anyone who Googles ‘how to treat a jellyfish sting’ will encounter authoritative web articles claiming the best thing to do is rinse the area with seawater, scrape away any remaining tentacles, and then treat the sting with ice,” said Dr. Angel Yanagihara, lead author of the paper and assistant research professor at the UHM. “We put those methods to the test in the lab, and found they actually make stings much, much worse.”

Researchers examined how different ways of removing tentacles affected the amount of venom injected during a sting: rinsing with vinegar or seawater; scraping with a credit card; or simply plucking them off. They also looked at whether treating with ice packs or hot packs reduced the damage done by the venom.

The team found that some of the most commonly recommended actions, including rinsing with seawater, scraping the tentacles, and applying ice, dramatically increased the severity of the stings.

“Less than one percent of stinging cells on a tentacle actually fire when you’re first stung,” explained Dr. Christie Wilcox, who aided in the study. “So anything you do that moves the tentacles or adherent stinging cell capsules around has the potential to increase the amount of venom injected into you by many fold.”

Instead of rinsing with seawater or scraping, researchers found that rinsing with vinegar (which irreversibly prevents the stinging cells from firing) or even simply plucking tentacles off with tweezers led to less venom injection. And after the sting, applying heat actively decreased venom activity. Applying ice not only didn’t help, for stings from the Hawaiian box jelly, it actually enhanced the venom’s activity to make stings cause more than twice the damage.

“It’s all too easy to find bad advice on treating jelly stings on the internet,” said Wilcox. But she also noted that such bad advice isn’t solely the fault of the sites that provide it. “Even in the peer-reviewed literature, there are a lot of examples of recommendations that are made in passing in discussion sections without any direct evidence to back them up, and then those just keep getting repeated and cited over and over even though they’re not based on rigorous, empirical scientific evidence.”