All children dream, and sometimes those dreams are nightmares. What can you do to help your child deal with frightening dreams? Talk with them. Don't tell them it's “just a dream.” Take it seriously.
If your child asks what you think the dream means, I always tell them that all I (or anyone) can do is imagine the dream they are sharing with me for myself, and go on from there to think and feel about what it means.
What if your child is too young to “talk” about the dream, or doesn't want to. What else to do? One can do very valuable & effective dream work with even very young kids by getting them to make drawings of their dreams, and using these drawings as "discussion prompters" when they tell the dreams. It is a good Idea to listen to the dream once, if they're willing to tell it, and then ask them to draw the picture(s) and tell the dream a 2nd time.
A very good resource for working with children's dreams is Dreamcatching: Every Parent's Guide to Exploring and Understanding Children's Dreams and Nightmares, by Kelley Bulkeley and Alan Siegel, Three Rivers Press, 1998.
The most emotionally urgent dream work with children usually comes when they share the nightmares that are "still bothering them" even after they wake up. Often, simply making the picture (first) and retelling the dream will accomplish the transformation of feeling that is desired (by both the child and the adult - usually a parent). This transformation of feeling is brought about through a number of factors: (1) having a trusted, loving adult pay serious, focused attention to the child's dream, (rather than dismissing it as "just a dream..."), (2) having the opportunity to "take control" of the "scary" images in the dream by drawing them, so that they are shaped by the child dreamer's hand, (rather than continuing to "shape" the child dreamer's feelings), and (3) having the whole "scene" of drawing and sharing the dream become an occasion for playful exploration and expression, (rather than an occasion for feeling scared. vulnerable, and emotionally alone.
For these reasons, often simply getting the child to draw the nightmare and tell it again, referring to the picture during the recitation, will be enough to transform his or her relationship to the dream. Sometimes, the child's feelings of fear and upset will persist even after this drawing/sharing. In that case, the next step is to get the child to draw and make a mask of the most threatening and scary figure/element in the dream. (I would recommend using a paper plate as the basic material for the mask.)
Once the mask is complete, I would recommend encouraging the child to put the mask over his/her face and playfully "act out" the character/situation in the dream. Usually, this will leave the dreamer cheerful and energized, and no longer feeling menaced and threatened by the dream memory. The reasons for the high success rate for this activity are the same as mentioned above, with the added emphasis on the "Gestalt" exercise of acting out the energy and activity of the scary dream figure. This activity integrates the interior energies that were denied and unconsciously projected into the scary figure to begin with. Acting out the dream with the mask causes the dreamer to "own", through play and imagination, the aspects of his/her own unconscious psychology that were projected and "disowned" and "forced" into the shape of the scary dream figure.
Burning the mask....
On very rare occasions, even this powerful "Shadow mask play" may not succeed in fully relieving the child dreamer's distress, in which case, a further step is in order. If the mask play still leaves the dreamer distressed and frightened, then helping the child to burn the mask is very likely to achieve the desired relief of feeling. Safety first, of course! Fireplaces are the best place for this activity, and fireplace igniters (rather than matches) are safest. Little hands should be held and guided by adult hands, but the child must be actively involved, and not just watch an adult burn the mask. It is also important for the mask to be mostly consumed and reduced to ash. Merely singeing the mask, or leaving large chunks unburned will probably not work in producing the desired transformation of emotion and feeling.
I believe that one of the reasons for this astonishingly high success rate is that "fire" is archetypal "patron of change" in the natural world. Things can be immersed in earth, air, and water, and not be fundamentally altered and changed, but nothing can be immersed in fire and remain unchanged. By helping the child dreamer to burn the mask into which the most disowned and distressing energies have been unconsciously projected, and consciously evoked, (in the acts of making the mask, and and using it to act out the most upsetting moments in the dream), the oldest and deepest symbolic powers of transformation and change are evoked in the dreamer's psyche. When these energies are recognized and better understood and integrated, they become the fuel for greater psycho-spiritual health and wholeness.
What else to do....
If this does not work, or if you don't feel comfortable pursuing these ways of working with your child's nightmares, there are many very, very good children's therapists available, many of whom would welcome working with your child's dreams.