Here are a few common fears children may develop some time before they are five. From the child's viewpoint, this reaction is very reasonable. The child has begun to associate protection and security with one special person. When that person leaves, the child doesn't know if the person will ever come back. He's only sure of what he can see and touch.
Many toddlers feel uneasy about even slight changes in familiar people or objects.
One boy refused to play with a beloved teddy bear after his well-meaning grandmother sewed on a new nose. To a young child, a thing is what it looks like. If mommy's looks change, the child isn't sure she's really mommy any more. While parents can't shield children from all changes, they can try to make changes as few and gradual as possible. Sometimes big changes are necessary, like a move to a new house.