It happens more often than many people think. Children, especially between the ages of 6 months and 5 or 6 years of age, love to put things in their mouths--and down it goes. It's part of their natural curiosity, but it can be dangerous.
Objects commonly swallowed by kids include coins, small parts of toys, buttons, and those little button batteries that power so many electronics and children's toys. These objects can get stuck in the esophagus, or get into the lungs, or pass through to the stomach and intestines.
Seek medical attention if, after swallowing an object, your child…
…is having frequent bouts of coughing or wheezing--this could indicate that the object got into the airway or lungs.
…is having obvious difficulty breathing. In this case, call 911 immediately--and while you wait for help, try the Heimlich Maneuver®.
…is gagging frequently, or is having difficulty eating or drinking. These might all be signs that the object has gotten stuck in the esophagus.
Also seek medical attention if your child has swallowed a button battery. Even if the child has no symptoms, these little power sources must always be located and taken out of the child because they contain acid that will cause damage to the body if the battery is allowed to remain inside.
Sometimes There's no Problem
Many children swallow objects and have no difficulties. (In fact, many swallowed objects are only found later, incidentally, when the child gets an x-ray for some other reason.) If your child is having no symptoms, it's okay to just watch them at home.
But Stay Vigilant
Today, many children's toys containing small parts are labeled "Not for children under 3 years old." But plenty of older children will also put objects in their mouths, and so the best thing to do is to continually remind your child to keep things away from their mouths. (I give my kids 1 warning and then, if I see a particular object near the mouth again, I throw it away.) Always try, too, to avoid giving coins to preschool- and early elementary school-aged children, unless you are going to supervise the situation; many kids in this age group still love to put loose change in their mouths.