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Cnidaria Envenomation Clinical Presentation

  • Author: Spencer Greene, MD, MS, FACEP; Chief Editor: Scott H Plantz, MD, FAAEM  more...
Updated: Feb 03, 2015


Three different mechanisms are responsible for toxicity from Cnidaria envenomations: immediate toxicity, immediate allergic reaction, and delayed allergic response.

When evaluating a patient with a suspected envenomation, it is essential to obtain the following information: (1) time of envenomation; (2) location of the incident; (3) description of the animal; (4) onset, progression, and quality of signs and symptoms; and (5) what treatments have thus far been attempted.

The severity of the envenomation is determined by a variety of factors, including (1) size, age, species, and overall health of the animal; (2) the size, age, and underlying health of the patient; (3) the surface area of the involved skin; and (4) the duration of contact.

Though not applicable to known envenomations, it is always wise to consider envenomation in the differential diagnosis of unexplained drowning and near-drowning.



Pain and dermatologic abnormalities are the most obvious, and often the only, signs and symptoms of a Cnidarian envenomation. Erythema develops rapidly after envenomation, followed by edema and purple-brown vesicular lesions, often found in a whiplike pattern. Most lesions last for minutes to hours, but some may hemorrhage or progress to full-thickness necrosis over the next 1-2 weeks.

Sea bather's eruption, or "sea lice", is characterized by small, intensely pruritic urticarial lesions confined to covered areas of the body. It develops when the larvae of several species of thimble jellyfish become trapped and maintain prolonged contact with the victim's skin. The lesions may last for up to 2 weeks but have no permanent consequences

Ocular abnormalities such as conjunctivitis, chemosis, corneal ulcerations, and lid edema have been observed following envenomations.

Findings indicative of systemic envenoming include pulmonary edema, variable blood pressure, tachycardia, weakness, headache, nausea, vomiting, muscle spasm, fever, pallor, syncope, respiratory distress, paresthesias, acute renal failure, hemolysis, myocardial infarction, and cardiopulmonary arrest.[10, 11] These are most likely to occur following envenomation from C fleckeri or P physalis. Oftentimes, the local findings are minimal.

Uncommon complications following Cnidaria envenomation include Guillain-Barré syndrome,[12] mononeuropathy,[13] and Takotsubo cardiomyopathy.[14]

The constellation of low back pain, abdominal cramping, nausea, vomiting, diaphoresis, headache, and tachycardia is suggestive of Irukandji syndrome.[15, 16] This entity, named for the Aboriginal tribe that formerly inhabited the areas in and around Cairns, Australia, was first described in 1952 by Dr. Hugo Flecker. In 1964, Dr. Jack Barnes identified C barnesi as the Cnidarian responsible for the condition, and since then other cubozoans have been implicated in the syndrome. Typically, 30 minutes after envenomation (range, 5 min to 2 h) patients develop the aforementioned signs and symptoms. Major envenomations also feature restlessness, agitation, and progress to pulmonary edema and cardiac failure.[17] Despite the severity of the systemic reaction, the findings at the envenomation site are barely detectable.



Contact with a Cnidarian is the cause of envenomation, although some patients have developed mild symptoms after ingestion of jellyfish.

Contributor Information and Disclosures

Spencer Greene, MD, MS, FACEP Director of Medical Toxicology, Assistant Professor of Medicine, Assistant Professor of Pediatrics, Section of Emergency Medicine, Baylor College of Medicine

Spencer Greene, MD, MS, FACEP is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American College of Medical Toxicology, East Texas Herpetological Society, Texas College of Emergency Physicians

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

A Antoine Kazzi, MD Deputy Chief of Staff, American University of Beirut Medical Center; Associate Professor, Department of Emergency Medicine, American University of Beirut, Lebanon

A Antoine Kazzi, MD is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Scott H Plantz, MD, FAAEM Associate Clinical Professor of Emergency Medicine, Department of Emergency Medicine, University of Louisville School of Medicine

Scott H Plantz, MD, FAAEM is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Additional Contributors

Dana A Stearns, MD Assistant Director of Undergraduate Education, Department of Emergency Medicine, Massachusetts General Hospital; Associate Director, Undergraduate Clerkship in Surgery, Massachusetts General Hospital/Harvard Medical School; Assistant Professor of Surgery, Harvard Medical School

Dana A Stearns, MD is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.


G Patrick Daubert, MD Assistant Professor, Assistant Medical Director, Sacramento Division, California Poison Control System; Director of Clinical and Medical Toxicology Education, Department of Emergency Medicine, University of California, Davis Medical Center

G Patrick Daubert, MD is a member of the following medical societies: American College of Emergency Physicians, American College of Medical Toxicology, American Medical Association, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Allison J Richard, MD Assistant Professor of Emergency Medicine, Keck School of Medicine of the University of Southern California; Associate Director, Division of International Medicine, Attending Physician, Department of Emergency Medicine, LAC+USC Medical Center

Disclosure: Nothing to disclose.

Chanida Sintuu, MD Resident Physician, Department of Emergency Medicine, LAC+USC Medical Center

Disclosure: Nothing to disclose.

Jeffrey R Tucker, MD Assistant Professor, Department of Pediatrics, Division of Emergency Medicine, University of Connecticut School of Medicine, Connecticut Children's Medical Center

Disclosure: Merck, Salary, Employment

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Cnidaria and jellyfish envenomations. Close-up photograph of sea anemone demonstrating tentacles surrounding the central mouth structure. Contact with tentacles results in discharge of nematocysts. Photo courtesy of Scott A. Gallagher, MD.
Cnidaria and jellyfish envenomations. Close-up photograph of a sea anemone demonstrating one of several tentacle types observed among different species. Photo courtesy of Scott A. Gallagher, MD.
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