Schizophrenia is a mental disorder in which patients see the world differently from the rest of the population, unable “to tell the difference between real and unreal experiences, to think logically, to have normal emotional responses, and to behave normally in social situations,” according to the National Institutes of Health (NIH). Hallucinations are one of the psychotic symptoms of schizophrenia, which involve hearing, seeing, feeling and smelling something that is not there. Schizophrenic hallucinations are considered a "positive" symptom, since it is a symptom that people usually do not have.
The National Institute of Mental Health (NIMH) notes that auditory hallucinations are the most common type of hallucination in schizophrenia. A patient with auditory hallucinations hears voices that are not there, which can incite panic. Examples of auditory hallucinations are the patient hearing the voices talk about her behavior, warn her about impending danger or talk among themselves. The voices may also order the patient to do something, which may be something the patient would not do on her own.
The second type of schizophrenic hallucination is visual hallucination, which the NIMH defines as the patient seeing people or objects that do not exist. The images can appear to be distorted or strange to the patient, and can also be frightening.
Some schizophrenic patients can experience tactile hallucinations, where the patient feels something that is not there. The NIMH gives the example of feeling like invisible fingers are touching the patient, even if there is no one close to the patient. Another tactile hallucination is the feeling of electricity moving through the patient's body.
The last type of hallucination in schizophrenia patients is olfactory hallucinations. During an olfactory hallucination, the NIMH notes that the patient will smell odors that no one else does. The perceived smell is usually an unpleasant odor. Sometimes, the patient will believe that the smell is coming from him, which can result in embarrassment if he believes the smell is foul.