A five-year-old boy needed emergency surgery after swallowing 52 toy magnetic balls - which stuck his appendix to his bowel.
Jude Foley, from Penydarren in Merthyr Tydfil, started suffering with sickness bugs last August which doctors initially thought were not serious.
However, as his stomach pains worsened his mother Lyndsey decided to take him to A&E at Prince Charles Hospital in Merthyr Tydfil.
An initial physical and blood examination showed nothing abnormal, but after an X-ray on Jude's stomach, a necklace-type shape could clearly be seen.
It was discovered that Jude had 52 magnetic balls - which can be stacked together to form different structures - stuck in the shape of a ring in his bowel.
He was then transferred by ambulance from Prince Charles to the Noah's Ark Children's Hospital of Wales in Cardiff and underwent a major operation in an attempt to remove them all safely.
"I felt like I might lose him - it was horrific," Lyndsey said.
"It was lucky that he was operated on that night or it could have been fatal. You don't expect something so bad to happen from a child's toy."
Doctors at the children's hospital had to cut Jude's bowel in five places as the magnets were trapped. They also had to remove his appendix as one of the magnets had joined it to his bowel.
Lyndsey added: "They operated as soon as we arrived. They told me the operation would take two hours but it ended up taking seven. The time went so incredibly slowly.
"As soon as he came out of surgery the surgeon said they'd managed to remove the 52 beads and that he was very lucky that there was no long-term damage.
"They did warn me before the surgery that he could end up with a colostomy bag for life and need monthly injections due to his bowel being so short. But he's very lucky. He can grow up and have no long-term issues."
Lyndsey said Jude took a couple of days to come round after the operation and was very sleepy and in a lot of pain.
"He was in for two weeks altogether. He was bed-bound for a week and was nil by mouth which was very traumatic for him. It was horrible for me too as I couldn't give him a cwtch as he was attached to all these difference machines."
Lyndsey believes that Jude didn't eat the magnetic balls all at once but did so over a much longer period of time.
She is now warning other families not to buy these types of toys over Christmas.
"If you have these beads at home remove them immediately. If you know of anyone who has them pass the message on.
"They are so dangerous they shouldn't be put on the market, and I wouldn't want another family to be put through what we have experienced."
Public Health Wales has said ingestion of mini magnets and button batteries can cause serious internal injuries if swallowed.
A spokesperson said: "Multiple magnets can stick together inside a child's stomach resulting in the need for major abdominal surgery. Studies show that in around 40% of cases, children swallow the item without anyone noticing. In many cases the child may not initially show any clinical symptoms or signs either."
Sarah Jones, consultant in environmental public health, said: "We are asking parents to think carefully before buying products containing magnets and button batteries for children.
"Mini magnet toys don't make good stocking fillers. They should always be stored out of the reach of small children. Similar dangers come from children swallowing button batteries too. Parents should make sure the button battery compartment is properly closed and secure on all toys before giving them to children."
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