Dunedin Hospital's emergency department does not often see patients who have swallowed button-sized batteries, ED clinical leader Dr Tim Kerruish says.
He estimated about one child would be seen a year and he was not aware of any long-term adverse effects from the Dunedin cases.
He was responding to a media statement from the Ministry of Consumer Affairs and Safekids New Zealand this week about the dangers of the small batteries which they said could cause significant and potentially fatal injuries from burns or tissue damage, in as little as two hours.
Such batteries were common in a wide variety of devices, including remote controls, singing Christmas cards, bathroom scales and car keys, they stated.
Dr Kerruish said the dangers of button batteries were well known. The cases seen in Dunedin were usually among 2 to 3-year-olds.
A child who had swallowed one of the batteries would be X-rayed to ensure it was not in the oesophagus, which was the main danger.
If it was there - and he had never seen a case of this - it would need urgent endoscopic removal.
If it was in the stomach, another X-ray would be required after 48 hours, to ensure it had passed into the small intestine, otherwise it would need to be removed.
Parents were advised to bring the child back immediately if they developed any symptoms.
Most batteries would pass through the alimentary canal within 48 hours.
His advice for parents was that it was wise not to let youngsters get their hands on the object in the first place.
He acknowledged this was easier said than done. His 3-year-old daughter had stuck a bead up her nose recently.
The ministry said at least four cases of injury through swallowing batteries had been reported in New Zealand, although less serious incidents were likely to be underreported.
Consumer Affairs principal adviser Martin Rushton said it was working with its counterparts overseas to look at longer-term measures that could reduce the risks.
