Health Library

What Are Jellyfish Stings?

Jellyfish have been around for millions of years and live in oceans all over the world. There are many different types of jellyfish. Some just look like small, clear blobs, while others are bigger and more colorful with tentacles hanging beneath them.

Jellyfish sting their prey with their tentacles, releasing a venom that paralyzes their targets. Jellyfish don’t go after humans, but someone who swims up against or touches one — or even steps on a dead one — can be stung all the same.

While jellyfish stings are painful, most are not emergencies. Expect pain, red marks, itching, numbness, or tingling with a typical sting.

But stings from some types of jellyfish — such as the box jellyfish (also called sea wasp) — are very dangerous, and can even be deadly. These jellyfish are most often found in Australia, the Philippines, the Indian Ocean, and central Pacific Ocean.

How Are Jellyfish Stings Treated?

Jellyfish stings leave thousands of very tiny stingers called nematocysts in the skin. These stingers can continue to release (or “fire”) jellyfish venom (poison) into the body. Treatment can vary based on the type of jellyfish most common in the area.

Often, it’s best to rinse a sting with vinegar. Vinegar is a weak acid that might keep the stingers from firing for some kinds of stings (especially from dangerous types like box jellyfish).

Do not rinse with fresh water (like tap or bottled water) because that can make more stingers fire. Rinsing a sting with seawater may prevent stingers from releasing more venom.

Also, do not scrape off any stingers still in the skin. This used to be recommended, but now is thought to make stings worse.

To deal with a sting:

• Remove your child from the water.
• Rinse the area with vinegar. (Keep a small plastic bottle of vinegar in your beach bag, just in case.)
• Don’t rub the area, which can make things worse.
• Use tweezers to pluck away any tentacles still on the skin. Do not scrape the area with a credit card or other stiff card.
• A hot (but not scalding) shower or soak may help lessen pain.
• Check in with your health care professional to see if pain relievers might help your child feel better.

Call an ambulance right away if someone has been stung and:

• has trouble breathing or swallowing
• has a swollen tongue or lips, or a change in voice
• has bad pain or feels generally unwell
• is nauseated or vomiting
• is dizzy or has a headache
• has muscle spasms
• has stings over a large part of the body
• the sting is in the eye or mouth
• might have been stung by a very dangerous jellyfish

Can Jellyfish Stings Be Prevented?

Beaches with lifeguards are more likely to warn visitors about jellyfish. Look for a sign or warning flag (some beaches fly a purple warning flag when there’s “dangerous marine life” in the water). Double check to make sure that you’ve got a small container of vinegar and a pair of tweezers in your beach bag.