Jellyfish stings are relatively common problems for people swimming, wading or diving in seawaters. The long tentacles trailing from the jellyfish body can inject you with venom from thousands of microscopic barbed stingers.
Jellyfish stings vary greatly in severity. Most often they result in immediate pain and red, irritated marks on the skin. Some jellyfish stings may cause more whole-body (systemic) illness. And in rare cases jellyfish stings are life-threatening.
Most jellyfish stings get better with home treatment. Severe reactions require emergency medical care.
In this post Pritish Halder describes the common signs and symptoms of jellyfish stings including:
- Burning, prickling, stinging pain
- Red, brown or purplish tracks on the skin — a “print” of the tentacles’ contact with your skin
- Throbbing pain that radiates up a leg or an arm
Severe jellyfish stings can affect multiple body systems.
These reactions may appear rapidly or several hours after the stings. Signs and symptoms of severe jellyfish stings include:
- Stomach pain, nausea and vomiting
- Muscle pain or spasms
- Weakness, drowsiness, fainting and confusion
- Difficulty breathing
- Heart problems
The severity of your reaction depends on:
- The type and size of the jellyfish
- Your age, size and health, with severe reactions more likely in children and people in poor health
- How long you were exposed to the stingers
- How much of your skin is affected
When to see a doctor
Seek emergency treatment if you have severe symptoms.
Jellyfish tentacles contain microscopic barbed stingers. Each stinger has a tiny bulb that holds venom and a coiled, sharp-tipped tube. The jellyfish uses the venom to protect itself and kill prey.
When you brush against a tentacle, tiny triggers on its surface release the stingers. The tube penetrates the skin and releases venom. It affects the immediate area of contact and may enter the bloodstream. Jellyfish that have washed up on a beach may still release venomous stingers if touched.
Types of jellyfish
While many types of jellyfish are relatively harmless to humans, some can cause severe pain and are more likely to cause a systemic reaction. These jellyfish cause more-serious problems in people:
- Box jellyfish. Box jellyfish can cause intense pain. Life-threatening reactions — although rare — are more common with this type. The more dangerous species of box jellyfish are in the warm waters of the Pacific and Indian oceans.
- Portuguese man-of-war. Also called bluebottle jellyfish, Portuguese man-of-war jellyfish live mostly in warmer seas. This type has a blue or purplish gas-filled bubble that keeps it afloat on the water and acts as a sail.
- Sea nettle. Common in both warm and cool seawaters, sea nettles live along the northeast coast of the United States and are abundant in the Chesapeake Bay.
- Lion’s mane jellyfish. These are the world’s largest jellyfish, with a body diameter of more than 3 feet (1 meter). They’re most common in cooler, northern regions of the Pacific and Atlantic oceans.
How is a jellyfish sting treated?
Most people don’t need to see their healthcare provider for a jellyfish sting. Depending on the type of jellyfish, you can administer first aid for most stings. You can treat mild jellyfish stings using the following steps:
- Wash the tentacles and venom off the affected area of your body with seawater. Don’t use freshwater.
- Using tweezers or gloved hands, remove any tentacles you see in your skin.
- Apply vinegar or rubbing alcohol to the affected area to stop any more firings of nematocysts. (You shouldn’t use vinegar for Portuguese man-of-war stings, though. It can cause more venom to be released from the nematocysts.)
- To help reduce the pain, you can put calamine lotion or hydrocortisone cream on a jellyfish sting. You can also use an ice pack or hot water to help with the pain and swelling.
If you seek medical care, your healthcare provider may treat more serious jellyfish stings with medication. Medications your healthcare provider may use include:
- Pain relievers: Pain relievers can help reduce your pain.
- Antivenin: Antivenin can help reverse the effects of the venom.
- Antihistamines: Antihistamines can help reduce itching and rash.
Does peeing on a jellyfish sting help?
No. You shouldn’t pee on a jellyfish sting. This old wives’ tale for how to cure a jellyfish sting has been around for a long time. The myth goes that if you apply urine to a jellyfish sting, you’ll counteract the venom. But no scientific studies back up this claim. In fact, peeing on a jellyfish sting could actually make the sting hurt worse.
How are jellyfish stings diagnosed?
Most jellyfish stings don’t require medical care from your healthcare provider. If you do seek treatment, your healthcare provider will probably be able to diagnose a jellyfish sting by looking at it. You may still have stingers in your injury. If so, your healthcare provider may collect a sample of the stingers to determine the appropriate treatment.
How can I prevent a jellyfish sting?
A jellyfish can sting you anytime they’re in or near the ocean, like on the beach. To reduce your risk of being stung:
- Ask lifeguards or park rangers if any jellyfish are present around your beach. (Some beaches post a warning flag when jellyfish are reported.)
- If you surf or dive in the ocean, wear a protective bodysuit.
- Never touch a jellyfish that’s washed up on shore. Dead jellyfish still have venom in their tentacles that can sting on contact.
Conditions that increase your risk of getting stung by jellyfish include:
- Swimming at times when jellyfish appear in large numbers (a jellyfish bloom)
- Swimming or diving in jellyfish areas without protective clothing
- Playing or sunbathing where jellyfish are washed up on the beach
- Swimming in a place known to have many jellyfish
Possible complications of a jellyfish sting include:
- Delayed hypersensitivity reaction, causing blisters, rash or other skin irritations one to two weeks after the sting
- Irukandji syndrome, which causes chest and stomach pain, high blood pressure and heart problems
The following tips can help you avoid jellyfish stings:
- Wear a protective suit. When swimming or diving in areas where jellyfish stings are possible, wear a wet suit or other protective clothing. Diving stores sell protective “skin suits” or “stinger suits” made of thin, high-tech fabric. Consider protective footwear as stings can also occur while wading in shallow water.
- Get information about conditions. Talk to lifeguards, local residents or officials with a local health department before swimming or diving in coastal waters, especially in areas where jellyfish
- Avoid water during jellyfish season. Stay out of the water when jellyfish numbers are high.
Outlook for a jellyfish sting?
The prognosis for a jellyfish sting depends on the type of jellyfish. Stings from some jellyfish cause only minor itching and pain. But some box jellyfish stings can kill you within a matter of minutes. Other box jellyfish stings can cause a fatal reaction four to 48 hours after a sting due to Irukandji syndrome. Irukandji syndrome is a delayed reaction to a sting.