I have no experience in this area at all. I am curious to know some examples of the tpye of hallucinations your difficult child has had. I just read the following to familiarize myself:
"A hallucination occurs when environmental, emotional, or physical factors such as stress, medication, extreme fatigue, or mental illness cause the mechanism within the brain that helps to distinguish conscious perceptions from internal, memory-based perceptions to misfire. As a result, hallucinations occur during periods of consciousness. They can appear in the form of visions, voices or sounds, tactile feelings (known as haptic hallucinations), smells, or tastes."
also:
"Hallucinations, particularly as described in the adult psychiatric literature, have been viewed as synonymous with psychosis and as harbingers of serious psychopathology. In children, however, hallucinations can be part of normal development or can be associated with nonpsychotic psychopathology, psychosocial adversity, or a physical illness (1). The first clinical task in evaluating children and adolescents is to sort out the most serious and worrisome hallucinations from those that are less pathological... The content of the hallucination may be relevant in understanding the underlying psychopathology and issues in the childs development"
Not sure if any of this helps - could you provide any more info?