Marine Stings – Jellyfish

Envenomation by jellyfish is a result of simultaneous discharge of many thousands of stinging capsules called nematocysts, normally located on the tentacles of the jellyfish.

These capsules contain small doses of venom that ‘fire’ into the skin like mini harpoons upon contact with the casualty. When a sting occurs torn off tentacles and capsules will be left on the casualty.  Not all capsules will ‘fire’!  It is important to stop these capsules from firing by providing the correct treatment for the type of jellyfish involved.

Tropical Envenomations

Potentially fatal envenomation is caused by two jellyfish types in Australian waters.

The Box Jellyfish

The Australian Box jellyfish has a large body up to 20-30cm and multiple tentacles. Contact with the tentacles causes severe immediate pain and whip-like marks on the skin. A sting with several meters of tentacles can cause respiratory and cardiac arrest within a few minutes.

Jellyfish causing Irukandji Syndrome

Approximately 10 small to medium-sized offshore and onshore jellyfish are known or suspected to produce an “Irukandji Syndrome”. These jellyfish only have four tentacles and some are too small to be seen by the victim.

A minor sting on the skin with no tentacle visible is followed in 5-40 minutes by severe generalized pain, nausea and vomiting, difficulty breathing, sweating, restlessness and a feeling of ‘impending doom’. There is potential for the victim to develop heart failure, pulmonary oedema and stroke.

Prevention of further stinging

When a sting occurs, pieces of tentacles and non discharged capsules may be left on the victim’s skin. In large or life-threatening stings it is very important to inhibit non-discharged capsules so that further treatment does not cause further envenomation.


Since it is usually difficult to recognize which species of jelly has caused a sting, management is based on the risk of serious stings in the known geographical location.

Jellyfish able to cause life-threatening stings primarily occur along the tropical coastline of Australia.