Emergency staff see at least two children a week who have swallowed button batteries, and that number is increasing.
Laptops, iPads, remote car keys, calculators, cameras and even musical greeting cards use the powerful lithium batteries, which can be deadly if swallowed.
The clinical director at Starship Hospital emergency department, Dr Michael Shepherd, said the little silver discs did horrendous damage.
"They should be locked away like household poisons," he said. "If swallowed, they cause damage very rapidly and if they get lodged in the body they need to be removed immediately under anaesthetic."
The danger comes from the electrical charge emitted when tissue wraps around the battery and connects the positive and negative terminals.
Surrounding tissue burns and can keep burning even after the battery has been removed.
Shepherd said manufacturers discussed improvements at the Safety 2012 conference in Wellington this week. They were considering a coating with a dye in it that would be released by contact with saliva.
"A lot of children are too young to say they have swallowed something, so something like a blue dye would alert the parent and they could get help sooner."
Changes could also be effected to make it harder for the body to connect batteries' positive and negative terminals. But Shepherd said changes were a long way off. He urged parents to educate children.
There had been no fatalities in New Zealand, but children had suffered permanent damage from swallowing the batteries or putting them in their ears or noses. In America, 12 deaths have been caused by them.
Silver snack threatens toddler's life
When Tom Sweeney found a silver battery in a drawer at home, he did what an increasing number of Kiwi kids do - he swallowed it.
The little boy had no idea the tiny lithium battery was so dangerous, and neither did his mum Olivia Sweeney.
Now the Whangarei mum is warning parents about the dangers of the batteries, which emit an electrical charge and can burn flesh.
That morning Tom had asked his mum to put the battery in an old toy, but was told it was the wrong size.
"Five minutes later he came in to me and said: 'Mum, it went down', and pointed to his throat."
Tom was taken to the doctor's for an X-ray and an ambulance was called to take them to Starship Hospital in Auckland.
"He had to go straight to hospital and we had to go to Starship because the instruments at Whangarei Hospital were too big to go down his esophagus."
Olivia said the two-hour drive to Auckland was a nervous time because the batteries could burn through flesh within two hours.
An X-ray later showed the battery had moved to Tom's intestine. Once a swallowed item passes through the two narrowest points of the esophagus and entrance to the stomach, it could usually pass through the rest of the body naturally.
Sweeney felt lucky her son was old enough to tell her he had swallowed the battery.