Parents, doctors and caregivers need to know that if a child swallows small, high-powered magnets, life-threatening problems can result, Canadian pediatricians warn.

Rare-earth magnets were created in the 1980s that are 10 to 20 times stronger than traditional magnets and are now widespread in desk toys, children's construction sets and jewelry.

In Monday's issue of the Canadian Medical Association Journal, doctors in Toronto illustrated the danger by describing how they had to treat a three-year-old boy with laparoscopic surgery after he ingested several small, spherical magnets that came together and tore a hole in his small intestine.

The only symptoms his mother noticed the first day was drooling. The boy was initially examined, X-rayed and discharged home to pass the magnet in his stool and his parents were told the signs were symptoms of intestinal perforation.

It was after having two watery bowel movements the next day and developing a fever of 38.7 C and fast heart beat that surgeons performed surgery to remove three neodymium magnets that were each five millimetres in diameter and repair the perforation. The boy had no complications after surgery and was discharged four days later.

Swallowing a single magnet is generally innocuous, Dr. Daniel Rosenfield of Toronto's Hospital for Sick Children and his co-authors said. But when multiple magnets are swallowed, especially at different times, they can attract each other through loops in the gastrointestinal tract, creating a force that can result in the death of tissue and eventual perforation.

In publishing the case, the authors called awareness and prevention the first defence.

"Although health care providers can play an important role in disseminating information on the risks of magnet ingestion, further targeted campaigns are needed to inform parents of the risks," the doctors wrote.

Small warning labels on products containing products haven't been enough to reduce cases, they said.

"Regulatory changes, health care provider awareness and parent education about magnet safety are important components in mitigating risks of magnet ingestion."

They suggested that healthcare providers use the 18-month visit to discuss magnet safety in the context of safe toys.

The Public Health Agency of Canada reported that between 1993 and 2007, there were 328 cases of children aged 13 years or younger who were brought to an emergency department because of an injury associated with magnets and nearly 55 per cent involved swallowing the magnets. Cases climbed sharply since the 1990s, the agency said.

While regulators in Australia and New Zealand have issued a ban on small, high-powered magnets from children's toys, construction kits and jewellery, Rosenfield 's team noted the restrictions don't cover products already sold or magnets in other products.

The authors also had suggestions for other doctors. Patients may present with vomiting, abdominal pain and fever that are common in children and can lead to delays in diagnosis, the study's authors said. They endorsed North American specialist guidelines that stress close monitoring, use of plain radiographic imaging and collaboration between primary care physicians, gastroenterologists and surgeons.

If possible, doctors can retrieve the magnets with endoscopy. If X-rays show the magnets moving through the GI tract, then they suggested discharging the child home with close follow-up and detailed instructions to parents, such as giving a laxative.