The RACQ LifeFlight Rescue helicopter airlifted the young boy from the island after he was stung on the upper leg just after 2.30pm on Wednesday.
He was swimming in a popular creek on the western side of the island, the same location where three young girls were stung on Tuesday.
The boy was flown to Hervey Bay Hospital in a stable condition.
A young female holidaymaker was airlifted from the same location after she was suspected to have been stung on the upper chest by an Irukandji about 11am on Tuesday.
She was in a stable condition when she was flown to Hervey Bay Hospital.
About an hour later, two sisters aged five and nine were playing in the water at the same creek when they both suffered stings to the upper body.
Queensland Ambulance paramedics treated them at the scene, before they were airlifted to Hervey Bay Hospital in a stable condition.
The Irukandji jellyfish is a small, extremely venomous species of box jellyfish about two centimetres in diameter, making it difficult to notice in the water.
Symptoms of being stung include shooting pains in the muscles, chest and abdomen; nausea; vomiting and breathing difficulties.
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