- The perception of auditory, visual, tactile, or gustatory sensations without an actual stimulus
- Etiology may be from underlying psychiatric disorder or organic cause.
- Mescaline (Peyote)
- Psilocybin/Mushroom Poisoning
- Ecstasy (MDMA)
- Bath Salts
- Salvia toxicity
- Toxic alcohols
- Flunitrazepam (Rohypnol)
- Gamma hydroxybutyrate (GHB)
- Chloral hydrate
Other Organic Causes
- Alcohol Withdrawal
- Anticholinergic Toxicity
- Tricyclic (TCA) Toxicity
- Ertapenem Toxicity
Psychiatric Causes 
- Schizophrenia, schizo-affective Disorder
- Parkinson's Disease
- Charles Bonnet Syndrome (in the visually impaired)
Workup should be targeted toward specific diagnosis. Cranial imaging is only useful if localized neurological findings or headache red flags
In non-auditory hallucinations, assume organic pathology until proven otherwise.
- If concerned for suicidal or unknown toxic ingestion:
- Tylenol level
- Treat the underlying pathology.
- In the case of Alcohol Withdrawl Hallucinosis, no standard therapy has been established, although treatment with neuroleptics (e.g. Haldol) has shown some benefit.  Also continue to treat the alcohol withdrawal.