A painful jellyfish sting may ruin your day at the beach, but don’t let it keep you out of the ocean for the rest of your vacation or the rest of the summer.

Diaphanous and dazzling, these strange marine creatures are found all over the world in all bodies of water — oceans, of course, but also lakes, rivers and any water with a connection to the ocean, according to The Nature Conservancy.

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How do they sting you? Their tentacles contain tiny barbs that penetrate your skin and release venom. Jellyfish can sting you in the water or after they wash up on land, so don’t assume that jellyfish you see lying motionless in the sand is dead and harmless. Some clear jellyfish, like moon jellies (Aurelia aurita), are indeed harmless and may cause skin irritation at most, while some pink ones, especially Pink Meanies, are highly venomous. However, experts warn that color and transparency are not reliable indicators of how dangerous a jellyfish is.

Box jellyfishBox jellyfish (Photo: Daleen Loest/Shutterstock)

Most of the jellies you encounter in the United States are the moon variety, whose sting is mild. Other relatively harmless ones include sea nettles, Lion’s mane and Cassiopea upside down jellies. But on rare occasion, the waters may contain box jellyfish, one of the most dangerous types. Their sting can cause extreme burning pain, difficulty breathing, dry mouth and anxiety. 

Box jellies are light blue, transparent and have a distinctive cube shape. Much more common in Australia, they can sometimes be found in warmer weather along the southeastern seaboard — even as far north as New Jersey. If there’s a suspicion of box jellies in the water and a swimmer encounters one, call 911.

If you see a jellyfish while you’re swimming, you’ll likely scramble to get away from it as quickly as possible. But what if you don’t spot it (which could easily happen, since they’re translucent) and you get stung?

“It’s important to look around the water immediately to see the size, shape and color of the jellyfish that caused the sting and to ask local lifeguards about the kinds of jellies that have been spotted in the area,” says Angel Yanagihara, PhD, a biochemist and assistant research professor at the University of Hawaii at Manoa.

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Signs of a jellyfish sting include:

  • Burning, prickling or stinging pain
  • Tracks on your skin (often red, brown or purple) where the tentacles touched you
  • Itching
  • Swelling
  • Tingling or numbness

Most stings can be treated with a few simple remedies.

Rinse, then repeat. Seawater can flush out pieces of jellyfish tentacles that tend to cling to the skin after a sting. Try not to get sand in the wounds or rub them with a towel, the Mayo Clinic advises. This can aggravate the stingers and cause more pain. You also can rinse the skin with vinegar for 30 seconds. “Vinegar isn’t really a treatment, as it won’t inactivate venom, but it’s useful for washing off tentacles,” explains Yanagihara.

Try hot water. This simple remedy can ease a painful sting, especially if you add Epsom salts to the water. “Water with these salts is a treatment that helps remove venom from the sting site,” says Yanagihara. Skip the ice packs though. They won’t neutralize the poison. The may lessen the pain temporarily, but it will just come back.  

Skip alcohol and urine. You may have heard that urine is a remedy for jellyfish stings, but don’t bother with it. “Urine won’t do any harm, but applying it to the affected area can lead to an infection if the site is scratched,” says Yanagihara. Pass on plain tap water, meat tenderizer and any agent or topical lotion that contains alcohol or menthol. “These last two substances cause the tentacles to explosively discharge venom, making the sting far worse.” 

Reach for an over-the-counter remedy. Check with your doctor about a taking an oral antihistamine or using a steroidal anti-inflammatory cream, both of which may counteract the venom, the Mayo Clinic recommends. But don’t rely on lidocaine or calamine lotion, as topical anesthetics and creams are ineffective and do little to reduce the impact of the venom. “A jelly sting isn’t like poison ivy,” reminds Yanagihara. 

Recovery from a jellyfish encounter depends upon the type of jellyfish, the location of the sting and the age and sex of the victim. For example, women and children have very thin skin along the neck and inner arms, while adult men have thicker skin over the back. Pain levels and recovery times for both groups will differ. A Portuguese man-o-war sting may take as little as an hour to stop hurting or symptoms could last for a couple of months; sea nettles may cause pain for 30 minutes or up to 2 weeks.

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Jennifer Kelly Geddes is a New York City-based writer and editor who specializes in parenting, health and child development. She’s also the mom of two teen girls.