Tourist lucky to survive irukandji sting

A Victorian tourist is lucky to be alive after being stung on the neck by a irukandji jellyfish in far north Queensland.

Ayllie White, 39, was snorkelling off Fitzroy Island last Friday when she was stung by the deadly, thumbnail-sized box jellyfish, Queensland Ambulance Service says.

Paramedics were initially concerned she was suffering an allergic reaction before toxicology results confirmed it was an irukandji sting.

She spent two days in intensive care at Cairns Hospital before being discharged on Wednesday.

Doctors told Ms White her heart slowed to a quarter capacity.

"It was a pretty dramatic reaction," she told ABC radio.