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.
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:
Call an ambulance right away if someone has been stung and:
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.
Reviewed by: Larissa Hirsch, MD
Date Reviewed: May 25, 2022