Someone who suffers from oneirophobia is fearful of what?

Oneirophobia (from Greek όνειρο (oneiro), meaning "dream", and φόβος (phobos), meaning "fear") is the fear of dreams.

It is generally accepted that phobias arise from a combination of external events (i.e. traumatic events) and internal predispositions (i.e. heredity or genetics). As with many phobias, onieraphobia can be traced back to a specific triggering event, like a traumatic experience at an early age. It is believed that heredity, genetics, and brain chemistry combine with life-experiences to play a major role in the development of this phobia.

As with any phobia, the symptoms vary by person depending on their level of fear. The fear is suffered due to experiences with frightening dreams (nightmares) or by negative events in the life affecting dreams. Primary symptoms of a typical person with onieraphobia is to trying to avoid falling asleep, causing extreme exhaustion. Other symptoms include extreme anxiety, dread and anything associated with panic attacks.