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Jellyfish stings

Erin N Marcus, MD, MPH, FACP
Geoffrey K Isbister, MD
Section Editors
Jan E Drutz, MD
Daniel F Danzl, MD
Deputy Editor
James F Wiley, II, MD, MPH


Jellyfish cause most marine envenomations in the United States and worldwide. There are more than 100 species of jellyfish, and the severity and treatment of their stings vary widely, depending upon the type of jellyfish, the size of the sting, and the individual patient.

This topic will discuss the clinical manifestations, diagnosis, and treatment of jellyfish stings. Recognition and treatment of marine envenomations by other animals are discussed separately. (See "Marine envenomations from corals, sea urchins, fish, or stingrays".)


Jellyfish are members of the phylum Cnidaria, as are sea anemones. Jellyfish are invertebrates that float in salt and brackish water. They have a central bell and lengthy tentacles that disconnect easily (picture 1 and picture 2). Jellyfish consume fish, crustaceans, and mollusks by injecting venomous capsules called nematocysts into their prey. The nematocysts are clustered along the jellyfish's tentacles and discharge rapidly on contact. Although Physalia sp (Portuguese man-of-war, also called bluebottle jellyfish), which are also members of the phylum Cnidaria, are not true jellyfish, they are discussed here as well.

Jellyfish nematocysts inject a mixture of proteinaceous toxins through hollow, barbed tubes into their victims' skin at an approximate force of 2 to 5 pounds per square inch [1]. The venom enters the dermis and general circulation and can cause both skin and systemic symptoms in affected patients.

Jellyfish do not actively seek out humans. However, they can be difficult to see, and most injuries occur when humans blunder into their tentacles.

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Literature review current through: Nov 2017. | This topic last updated: Oct 21, 2016.
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