Why does my toddler have nightmares?

Children have bad dreams for the same reasons that adults have bad dreams: they express the dreamer's fears, anxieties and stress. The monsters, witches or evil creatures in bad dreams very often symbolize the child's own "naughty" urges and desires, such as wanting to smack a sibling or being angry at Mommy. By venting these feelings in the security of sleep, the child is better able to control impulses in real life.