The oceans of northern Australia coastal beaches harbor numerous venomous jellyfish. Several species cause Irukandji Syndrome, a severe disorder (developing within an hour after a sting) consisting painful muscle cramps, vomiting, sweating, agitation, vasoconstriction, prostration, hypertension, cardiac irregularities. The jellyfish toxin may modulate neuronal sodium channels leading to a massive release of endogenous catecholamines. Segmental sympathetic cardiovascular hyperactivity has been emphasized but this case report portrays a dramatic effect on segmental sympathetic sudomotor function.