Just like batteries, those small, round magnets can be particularly hazardous if ingested. “They can bunch together in the intestines,” Burgert says. “Magnets can cut off circulation and lead to perforations if left for too long.” Even worse, kids can pop them in their mouths and swallow—and you’d never know. “These can be silent ingestions, and treatment may be delayed. Magnets in the gut may need to be surgically removed.” If your child ingests magnets by accident, he needs prompt medical attention. Call your pediatrician immediately.