Hallucinations are sensations that appear to be real but are created within the mind. Examples include seeing things that are not there, hearing voices or other sounds, experiencing body sensations like crawling feelings on the skin, or smelling odors that are not there. Hallucinations can be a feature of psychotic disorders such as schizophrenia and are also very common in drug-induced states and in drug withdrawal. This occurs with a number of different drugs. People who are seriously ill, such as those with liver failure or kidney failure, can experience hallucinations. High fevers can also produce hallucinations in some people. Hallucinations can accompany other psychotic symptoms such as delusions and disconnection from reality. They can be temporary or persist over the long term, depending upon the exact type of hallucinations and their cause.

REFERENCE:

Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.