Virtually any object small enough to pass through the pharynx may be swallowed.
The objects most frequently ingested by younger children are coins, but also include small toys, pencils, pen lids, button batteries, safety pins, needles, buttons and hairgrips. These are often radio-opaque.
This is a companion discussion topic for the original article at https://patient.info/doctor/paediatrics/swallowed-foreign-bodies