Irukandji syndrome is a condition that results from envenomation by certain box jellyfish. In rare instances the sting may result in cardiac arrest and death. The most common jellyfish involved is the Carukia barnesi, a species of Irukandji jellyfish. Those stung may experience severe or even excruciating pain. The syndrome was given its name in 1952 by Hugo Flecker, after the Aboriginal Irukandji people who live in Palm Cove, north of Cairns, Queensland, Australia, where stings are common. Signs and symptoms Most stings occur during the summer wet season in October–May in North Queensland, with different seasonal patterns elsewhere. Because the jellyfish are very small, the venom is only injected through the tips of the nematocysts (the cnidocysts) rather than the entire lengths; as a result the sting may barely be noticed at first. It has been described as feeling like little more than a mosquito bite. The symptoms, however, gradually become apparent and then more and more intense in the subsequent 5 to 120 minutes (30 minutes on average). Irukandji syndrome includes an array of systemic symptoms, including severe headache, backache, muscle pains, chest and abdominal pain, nausea and vomiting, sweating, anxiety, hypertension, tachycardia, and pulmonary edema. Symptoms generally improve in four to 30 hours, but may take up to two weeks to resolve completely. Toxicity When properly treated, a single sting is almost never fatal; however, two people in Australia are believed to have died from Irukandji stings, which has greatly increased public awareness of Irukandji syndrome. It is unknown how many other deaths from Irukandji syndrome have been wrongly attributed to other causes. Pathophysiology The exact mechanism of action of the venom is unknown, but catecholamine excess may be an underlying mechanism in severe cases. Animal studies appear to confirm a relationship between envenoming and an increase in circulating noradrenaline and adrenaline. Treatment Similar to other box jellyfish stings, first aid consists of flushing the area with vinegar to neutralize the tentacle stinging apparatus. As no antivenom is available, treatment is largely supportive, with analgesia being the mainstay of management. Nitroglycerin, a common drug used for cardiac conditions, is utilised by medical personnel to minimise the risk of pulmonary edema and to reduce hypertension. Antihistamines may be of benefit for pain relief, but most cases require intravenous opioid analgesia. Fentanyl or morphine are usually chosen. Pethidine (meperidine, brand name Demerol in the US) should be avoided, as