But one mum found out the hard way – when her 16-month-old son swallowed an astonishing 42 fridge magnets. FORTY TWO!
The mum, from Chelyabinsk, Russia, panicked when she noticed that all of the magnets from the family's fridge had gone missing after leaving her toddler in the kitchen.
She rushed him to a clinic where amazed doctors scanned the boy and found a huge quantity of small, round magnets in his abdomen. He was then admitted to hospital where surgeons immediately operated.
"The child had been in the room alone with the magnets and now they were gone. She thought he must have swallowed them," said a clinic spokesman.
Surgeons confirmed her fears when ultrasound scans found 42 magnets in the child's digestive system.
Chief paediatric surgeon Nikolay Rostovtsev - who performed the surgery - said: "Over the years, I had to take a variety of foreign bodies including magnets from young patients.
"Once I removed about 20 of them, but this incident of our little patient has broken all records."
The boy is now recovering from the adominal operation at Chelyabinsk Oblast Children's Hospital.