Cnidarian, or jellyfish, stings are a common cause of emergency room visits in tropical coastal regions. Cnidarians have tentacles containing thousands of stinging cells, called nematocytes, that fire toxins upon physical contact.

Symptoms include intense pain, blistering, and localized skin necrosis (cell death). Malaise, weakness, fever, chills, muscle spasms, nausea, and vomiting may also occur. On rare occasion, certain types of jellyfish (such as the Chironex fleckeri box jellyfish in Australia) can cause paralysis and even death.

1

Jellyfish Sting on Knee

Jellyfish stings have a distinctive look. The sting will commonly leave a "print" of the tentacle with red, brown, or purplish track marks along the skin. The physical markings will usually be accompanied by:

Burning, prickly, or stinging sensations
Itching
Localized swelling
A throbbing pain radiating up up a leg or arm

Jellyfish stings can usually be diagnosed by appearance alone, although they are often mistaken for stings from other sea creatures, including Portuguese man o' wars, blue bottles, puffer fish, and sea anemones.

Seek emergency care if you develop signs of a potentially life-threatening allergy known as anaphylaxis, including shortness of breath, hives, rapid heartbeat, nausea, confusion, and the swelling of the face, tongue, or throat.

2

Jellyfish Sting on Knee After 2 Days

Healing Bumps from the Tentacle's Path — Erin/Flickr Creative Commons

Two days after a jellyfish sting, the skin will have undergone healing but will still show evidence of the tentacle marks. A rash or other skin reaction can sometimes develop due to a delayed hypersensitivity reaction. These can usually be treated with oral antihistamines or corticosteroids.

Tylenol (acetaminophen) or over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) like Advil (ibuprofen) or Aleve (naproxen) can help relieve the pain.

3

Jellyfish Sting on the Torso

Inflammation Shows the Shadow of the Stinging Jellyfish — Pete & Brook

Contact with a jellyfish tentacle can trigger thousands of nematocysts to pierce the skin and inject toxins. Depending on the species and the number of stings delivered, the reactions can range from mild to severe. If there are multiple stings, the venom can sometimes consolidate in the capillaries and cause areas of patchy redness, swelling, and a burning sensation.

The first step in treating a jellyfish sting is to remove any parts of the tentacle still attached to the skin—but not with your bare hands. Even if the tentacle is no longer attached to the creature, it can keep contracting and injecting toxins into the skin. The best ways to remove a tentacle is with gloves, a brush, or even the edge of a credit card.

4

Jellyfish Sting on Arm

A Jellyfish Attacks in an Exotic Location — Kate Nevens/Flickr Creative Commons

There is an ongoing debate about the best way to treat a jellyfish sting. In one camp, there are those who insist that distilled white vinegar will "neutralize" the toxins. Others insist that the body part should be soaked for 20 to 45 minutes in hot water 110 to 113 F (43 to 45 C) to draw out the toxins. If there are any remaining stingers in the skin, you can use a pair of tweezers to pluck them out.

Some people will use all of these methods, soaking the skin in vinegar for 30 seconds before removing the remaining stingers, followed by 20 for 40 minutes in hot (not scalding) water.

Using a cold compress after the initial treatment may help alleviate some of the pain and inflammation.

5

Man-O-War Sting

Oh! Man-O-War this Looks Painful! — Portuguese man o' war sting.
Simon Tonge/Flickr Creative Commons

Jellyfish stings can be distinguished from other stings by the narrow trail of tentacle marks they leave. Other jellyfish-like creatures, such as the Portuguese man o' war, tend to leave wider marks on the skin and larger areas of redness, swelling, inflammation.

Pufferfish stings, by contrast, are more diffuse and irregular in their markings with a localized cluster of raised lesions. Anemone stings are similar but will be more tightly clustered and sometimes develop blister-like lesions that ooze.

Learning the difference between the various sea creature stings can ensure the most appropriate treatment and care. Some stings, like those from a man o' war, can be especially severe.

While man o' war stings can cause extreme pain, they are rarely deadly. Far more serious is the box jellyfish of Australia which has caused eight deaths since 2000 (two in 2016 alone).

6

Jellyfish Sting to the Neck

More than Jellyfish Can Sting in the Ocean — Mat Honan

Jellyfish stings to the face or head will usually not leave scars if treated appropriately. The only concern is if a sting occurs in or around the eye. In such case, it is important that you thoroughly flush the eye with water and either go to the nearest emergency room or call 911 if you can't drive yourself.

An ophthalmologist will most likely need to see you to remove any remaining stingers and assess the injury. Oral antibiotics will usually be prescribed to prevent infection and reduce the risk of eye damage.

7

Sea Anemone Sting

Whatever the cause of the sting, there are home-spun remedies you should avoid to keep a bad situation from turning worse. Among the things to avoid:

Rinsing a sting with urine
Applying meat tenderizer
Applying alcohol or ammonia
Applying pressure bandages
Rubbing the skin with sand
Rubbing the skin with seaweed
Soaking the skin with fresh water (which can release even more venom)

8

Jellyfish Sting on the Feet

Jellyfish stings on feet — bobafred/Flickr Creative Common

Most jellyfish stings do not require medical care and can be effectively treated at home. With that being said, the severity of a sting can vary based upon:

The type of jellyfish you encounter
The number of stings you incur
The amount of skin affected
The duration of the exposure
Your age, general health, and medical conditions (such as a heart problem or a history of anaphylaxis)

Because of their smaller size, young children are prone to more serious reactions and should always be seen by a doctor. Reactions may appear rapidly or several hours after the sting.

Jellyfish Sting Pictures

What They Look Like and How to Treat Them