Generally it is not harmful if the child swallows a chewing gum once or twice.
Children under 5 should not be given any chewing gums because they don’t
understand the difference between swallowing and chewing. In case if they have
already swallowed, there is not much to worry. A chewing gum has a gum base
which is indigestible. But it doesn’t stay in your child’s stomach. It moves
relatively intact through the digestive system and is excreted via stool in a
day or two. On very rare occasions, large amount of swallowed gum can combine
with constipation and block a child's intestine.