Jellyfish Stings

Jellyfish are sea creatures that live in all of the world’s oceans. They have soft, bell-shaped bodies with lengthy, finger-like structures called tentacles. Jellyfish have stinging cells called nematocysts inside of their tentacles. A single tentacle may contain thousands of nematocysts.

Nematocysts contain a poisonous substance (venom) that helps jellyfish protect themselves. The venom also helps them capture food by stinging it. Jellyfish don’t usually mean to sting humans. They sting when you brush up against them while swimming or walking along the beach.

Most jellyfish stings are harmless. But some jellyfish stings can cause serious harm. If you or someone you’re with is stung, get help right away. If you’re experiencing life-threatening symptoms such as difficulty breathing, call 911 or go to your nearest emergency room.

How do jellyfish sting?

Jellyfish don’t intentionally mean to sting humans. But if you brush by one or accidentally step on one, it stings you to protect itself.

Each nematocyst in a jellyfish’s tentacle contains spring-loaded barbed threads, or tubules. When triggered, a large concentration of calcium passes over the jellyfish’s plasma membrane. This leads to increased pressure inside the nematocyst. The increased pressure causes the threads to uncoil and spring out like tiny darts, firing venom into an unsuspecting victim. The entire process takes a fraction of a second.

Moreover, nematocysts can fire their venom even when they’re unattached from the jellyfish. They can also fire their venom if the jellyfish is dead.

How common are jellyfish stings?

As many as 150 million jellyfish stings occur around the world each year.

How does a jellyfish sting affect my body?

The reaction you receive from a jellyfish sting depends on many variables. Some jellyfish stings only cause minor irritation, and some stings can be fatal. The factors that influence what type of reaction you may have include:

• Type of jellyfish.
• Your age, health and body weight.
• Where on your body you were stung.
• The surface area of your exposed skin.
• How long the venom has been in your body.

What types of jellyfish can cause serious harm?

There are thousands of different types of jellyfish in the oceans around the world. While some can be harmless, there are others you need to watch out for and avoid. Some of the jellyfish whose stings can cause serious harm include:

Box

The box jellyfish is the most deadly jellyfish in the world. Sometimes called sea wasps, they have box-like bodies with tentacles extending from each corner. Box jellyfish live in tropical areas around the world. They’re commonly found on the northern coast of Australia and the Indo-Pacific Ocean. There are more than 40 species of box jellyfish. The Australian box jellyfish is the most venomous jellyfish in the world.

Lion’s mane

The lion’s mane jellyfish is the largest jellyfish in the world. They can grow up to more than 3 feet wide, and their mane-like tentacles can grow up to 120 feet long. Lion’s mane live in cooler climates in the Arctic Ocean and the North Pacific Ocean. Their name comes from the hundreds of sting-covered tentacles that make up their mane.

Sea nettle

The sea nettle jellyfish is one of the most common jellyfish found along the Atlantic, Pacific and Gulf coasts. They’re another large jellyfish that can grow more than 1 foot wide. Each sea nettle has 24 tentacles that can grow up to 6 feet long.

Portuguese man-of-war

The Portuguese man-of-war isn’t technically a jellyfish, but they look like one. These creatures live in the tropical waters of the Atlantic, Pacific and Indian oceans and the Caribbean Sea. Portuguese man-of-war have balloon-like floats that keep them above the water. Below the water, they have long strands of tentacles and polyps that grow to about 30 feet long.