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Toxicology – Jellyfish Envenomation
Source
Jellyfish are marine invertebrates belonging to the phylum Cnidaria, with thousands of species found worldwide. They are characterized by a bell-shaped body, trailing tentacles, and specialized stinging cells called nematocysts. Jellyfish are commonly encountered in coastal waters, particularly during warmer months, and often travel in groups.
Typical Presentation
Individuals typically present after sudden contact with tentacles while swimming, followed by immediate sharp pain and visible linear skin markings at the site of contact.
Clinical Features
Common Jellyfish
Stings usually cause painful, raised skin lesions resembling hives, sometimes with blistering, bleeding, or tissue damage. Associated symptoms may include swelling, weakness, headache, nausea, and vomiting.
Box Jellyfish
These are among the most dangerous species. Envenomation can cause severe pain, dark linear skin markings, muscle spasms, and systemic symptoms such as fever, nausea, and cardiovascular instability. In severe cases, rapid progression to cardiac or respiratory failure may occur.
Portuguese Man-of-War
Although not a true jellyfish, it causes similar but often more severe reactions, with a higher risk of systemic complications
.
Irukandji Syndrome
Following envenomation by certain small jellyfish, symptoms may initially be mild but progress within minutes to severe back pain, muscle cramps, abdominal pain, sweating, headache, hypertension, and tachycardia.
Mechanism of Action
Jellyfish deliver venom through nematocysts located on their tentacles. Upon contact, these structures discharge microscopic barbs that penetrate the skin and inject venom, causing immediate pain and inflammation.
Management
Initial treatment involves removing the person from the water and rinsing the affected area with seawater to prevent further nematocyst discharge. Vinegar may be applied in some cases to deactivate stinging cells before carefully removing any remaining tentacles. Most cases are self-limited, but severe envenomations—particularly from box jellyfish—may require antivenom and advanced supportive care.
Key Points
Source
Jellyfish are marine invertebrates belonging to the phylum Cnidaria, with thousands of species found worldwide. They are characterized by a bell-shaped body, trailing tentacles, and specialized stinging cells called nematocysts. Jellyfish are commonly encountered in coastal waters, particularly during warmer months, and often travel in groups.
Typical Presentation
Individuals typically present after sudden contact with tentacles while swimming, followed by immediate sharp pain and visible linear skin markings at the site of contact.
Clinical Features
Common Jellyfish
Stings usually cause painful, raised skin lesions resembling hives, sometimes with blistering, bleeding, or tissue damage. Associated symptoms may include swelling, weakness, headache, nausea, and vomiting.
Box Jellyfish
These are among the most dangerous species. Envenomation can cause severe pain, dark linear skin markings, muscle spasms, and systemic symptoms such as fever, nausea, and cardiovascular instability. In severe cases, rapid progression to cardiac or respiratory failure may occur.
Portuguese Man-of-War
Although not a true jellyfish, it causes similar but often more severe reactions, with a higher risk of systemic complications
.
Irukandji Syndrome
Following envenomation by certain small jellyfish, symptoms may initially be mild but progress within minutes to severe back pain, muscle cramps, abdominal pain, sweating, headache, hypertension, and tachycardia.
Mechanism of Action
Jellyfish deliver venom through nematocysts located on their tentacles. Upon contact, these structures discharge microscopic barbs that penetrate the skin and inject venom, causing immediate pain and inflammation.
Management
Initial treatment involves removing the person from the water and rinsing the affected area with seawater to prevent further nematocyst discharge. Vinegar may be applied in some cases to deactivate stinging cells before carefully removing any remaining tentacles. Most cases are self-limited, but severe envenomations—particularly from box jellyfish—may require antivenom and advanced supportive care.
Key Points
- Detached tentacles can still sting and should be handled carefully.
- Most jellyfish stings are mild and resolve without complications.
- Vinegar may worsen stings from certain species, so use should be species-appropriate.
- Even dead jellyfish can still cause envenomation.
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