Jellyfish Sting: Symptoms & Treatment

Instructor: Amanda Robb

Amanda has taught high school Biology & Physics for 8 years. She received her M.Ed. from Simmon's College and M.S. from Tufts in Cellular and Molecular Physiology.

In this lesson we'll be exploring the painful world of jellyfish stings. Here you'll learn to identify the symptoms of a jellyfish sting and ways to treat them. We'll look at differing levels of severity of stings as well.

What Is a Jellyfish Sting?

The ocean is an oasis on a hot summer day. Running over the scorching sand, you head straight into the waves. However, all around you people are running the opposite direction. As you search the sea, you notice tiny white objects in the ocean. They look almost like plastic bags drifting around in the current. Suddenly, you feel a stinging sensation on your leg. Looking down, you see the shapes are not plastic bags, but jellyfish. Your leg starts to turn red and swell, but the pain isn't too bad. Escaping like the rest of the beach goers, you stop on the shoreline to inspect your jellyfish sting.

Jellyfish are marine invertebrates dwelling in both warm and cool waters. Jellyfish range from tiny box jellyfish to giant lion's mane jellyfish, which can reach up to over two meters in diameter. When you brush up against a jellyfish, stinging cells are activated and release tiny tubes of poison that penetrate your skin. The poison is what causes pain, swelling, and other symptoms from the sting.


The symptoms from jellyfish stings can range from a mild burning sensation to severe muscle cramps, difficulty breathing, and even death. Let's look at different symptoms for common jellyfish stings.

Sea Nettle

Sea nettles are the beautiful classic jellyfish that come to mind when talking about these animals. With tentacles reaching up to 15 feet long, these jellyfish can look quite majestic until you touch one of them. Fortunately, sea nettle stings are relatively mild. For most stings, you'll only experience a mild skin rash. However, if you happen to come across a swarm of sea nettles, multiple stings can result in muscle cramps and even difficulty breathing. There are different species of sea nettles found in many regions of the world, such as both the east and west coast of the United States.

Welts produced from a jellyfish sting
jellyfish sting

Lion's Mane

Don't think you're immune to jellyfish stings by staying in cooler water. The lion's mane jellyfish dwells in the cold waters of the Pacific and Atlantic Ocean. Luckily, this jellyfish is quite large and easy to spot, with a diameter of over two meters, and has very long, numerous tentacles. If you are unlucky enough to be stung by a lion's mane jellyfish expect difficulty breathing, severe muscle cramps and even skin blistering, as the toxins are severe.

Cyanea capillata is one of the largest jellyfish
lions mane jellyfish

Box Jellyfish

Box jellyfish are the most dangerous type of jellyfish and one of the most poisonous animals in the ocean. A sting from a box jellyfish (also called a sea wasp due to the pain it can cause) is enough to send a man into cardiac arrest. Box jellyfish are a huge problem in the warm waters of Australia.

The most severe stings can result in difficulty breathing, collapse, muscle cramping and spasms, death of tissue where stung, chest pain, changes in pulse, nausea and vomiting. There are over 40 species of box jellyfish and not all are so deadly. Less toxic stings will produce red welts, stinging, swelling, headaches, and sweating.


Luckily, as people emerge from the water with jellyfish stings there are things you can do to help right away, as well as treatments that medical professionals can provide.

First Aid

The first step for a jellyfish sting is always to call a medical professional immediately. If you can, include the age, weight, any medical conditions of the victim, and the type of jellyfish.

While you wait for help to arrive, there are a few things you can do. First, pour vinegar on the sting. The vinegar disarms the stinging cells and prevents them from releasing toxins into the skin. Vinegar works for most jellyfish stings.

Signs in Australia for treating jellyfish stings
jellyfish sting sign

If vinegar isn't available, you can rinse the area with sea water to try to remove any stingers. If available, mix a small amount of baking soda in with the sea water. However, do not rinse the wound with freshwater as this can activate the stinging cells even more. Avoid scrubbing the area with any liquid and make sure to keep sand out of the wound. After the area has been cleaned, anti-inflammatory creams can be used topically to treat the area, and antihistamine medication may be given.

If the person has lost consciousness and is no longer breathing, a certified bystander can provide CPR until emergency medical personnel arrive.

Although there is a myth that urinating on a jellyfish sting will help heal the wound, this is not recommended. Not only is it gross, but it also doesn't help deactivate the stingers like vinegar or seawater.

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