The craze, which swept the US before becoming popular in the UK, sees kids put ice onto a layer of salt on their skin, sparking a burning reaction similar to frostbite.
One schoolboy from Swansea was left so badly burnt after doing the challenge that doctors considered giving him a skin graft.
His mum has warned others about the dangers of the craze and said: “It is so deep that it has burnt all the nerve endings."
“It is like severe frostbite. It could have gone septic and caused organ failure. He is looking a bit sheepish now.”
A mother from Fife also shared a picture of the “permanent scars” her daughter suffered after trying the challenge
Doctors decided against giving the boy a skin graft because he still had full movement in his hand.
“At first I thought it was a cut so I took him to the minor injuries unit and it was treated as such,” she said.
“Then when I realised what had happened and it was a burn he was taken to the burns unit.
“The consultant said he had never seen an ice cube do this much damage.”