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 it, 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 one that is dead.

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 can also warn other swimmers. It's helpful to know what kind of jellyfish stung you. Your lifeguard may 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.

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

• Rinse the area with seawater. (Fresh water could make it worse.) Avoid rubbing the area, which also can make things worse.
• With many types of jellyfish stings, it helps to soak the area of skin with vinegar for 15 to 30 minutes.
• Use a credit card to scrape off the stingers still in your skin. If available, put shaving cream or a paste of seawater and baking soda on the area. Then scrape it off (kind of like pretend shaving).
• Check with your doctor. Using certain creams or pain relievers may help you feel better.

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

• having trouble breathing or swallowing
• has a swollen tongue or lips, or a change in voice
• has bad pain or feels generally unwell
• has stings over a large part of the body
• has been stung in the eye or mouth

What About Pee for a Jellyfish Sting?

You may have heard people say you should pee on a jellyfish sting. First off, ew! Secondly, experts say that's not necessary. Seawater and 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 many 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: August 2011