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What Are Jellyfish?

Jellyfish live in the ocean and usually don't bother anyone. They just float around and look weird, sometimes washing up on the beach.

A jellyfish jiggles like gelatin, and some just look like small, clear blobs. But others are bigger and more colorful with a bunch of tentacles that hang down underneath them, kind of like an octopus.

Beware those tentacles! Jellyfish need to eat in the ocean, so their sting helps them catch other sea creatures. Unfortunately, that sting can be turned on people. Jellyfish can sting with their tentacles if they brush against you when you're swimming in the ocean. You also can get stung if you step on a jellyfish, even a dead one.

Usually, jellyfish stings will hurt, but are not emergencies. Most cause pain, red marks, itching, numbness, or tingling. But a few types of jellyfish (mainly found in Australia, the Philippines, the Indian Ocean, and central Pacific Ocean) are very dangerous, and can cause people to get very sick quickly.

What If You Get Stung By a Jellyfish?

If you get stung, take these two steps right away:

  1. Get out of the water.
  2. Tell an adult.

See the lifeguard next, if there's one at your beach. He or she may be able to help and also can warn other swimmers. It's helpful to know what kind of jellyfish stung you. Your lifeguard might be able to tell you what type is usually at that beach.

One Jellyfish Sting = Thousands of Tiny Stingers

Jellyfish stings aren't like bee stings when it comes to the stinger. A bee sting leaves behind a single stinger that you can usually see and pull out.

When a jellyfish stings a person, it leaves thousands of very tiny stingers called nematocysts in the skin. These stingers can continue to release jellyfish venom (poison) into the person's body. Sometimes, they can be rinsed off with seawater. They also can be scraped off using something like a credit card, not your hand.

Here's what a parent or other adult can do to help you feel better if a jellyfish stings you:

Someone needs to call for an ambulance right away if a person who's been stung:

What About Pee for a Jellyfish Sting?

You may have heard people say you should pee on a jellyfish sting. First, ew! Second, experts say that's not necessary. Seawater and sometimes vinegar are recommended instead. Yes, vinegar — the same stuff you might use in a salad dressing.

Why does vinegar work sometimes? Vinegar is a weak acid. For some kinds of jellyfish stings, that chemical makeup may keep the nematocysts from "firing," or releasing venom. Remember that nematocysts are the tiny stingers the jellyfish leaves behind in someone's skin.

That's why seawater is best for rinsing off. Seawater — the jellyfish's home environment — doesn't seem to cause the stingers to fire or not fire. But fresh water (like the kind from your tap or in bottled water) is unfamiliar and may cause the stingers to fire.

Avoiding Jellyfish Stings

Reduce your chances of getting stung by a jellyfish by swimming only at guarded beaches. You're more likely to get a warning about jellyfish at a beach that has lifeguards. They might post a sign or fly a warning flag.

Some beaches fly a purple warning flag whenever there's "dangerous marine life" in the water. So if the purple flag is flying, find out why!

Reviewed by: Larissa Hirsch, MD
Date reviewed: June 2014

Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

© 1995-2015 KidsHealth® All rights reserved.
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