Hallucinations involve sensing things while awake that appear to be real, but instead have been created by the mind.
Common hallucinations include any of the following:
- Feeling bodily sensations, such as a crawling feeling on the skin or the movement of internal organs.
- Hearing sounds, such as music, footsteps, windows or doors banging.
- Hearing voices when no one has spoken (the most common type of hallucination). These voices may be critical, complimentary, neutral, or may command someone to do something that may cause harm to themselves or to others.
- Seeing patterns, lights, beings, or objects that are not there.
- Smelling a foul or pleasant odor.
In some cases, hallucinations are normal. For example, hearing the voice of, or briefly seeing, a loved one who recently died can be a part of the grieving process.
There are many causes of hallucinations, including:
- Being drunk or high, or coming down from such drugs as marijuana, LSD, cocaine (including crack), PCP, amphetamines, heroin, ketamine, and alcohol
- Delirium or dementia (visual hallucinations are most common)
- Epilepsy that involves a part of the brain called the temporal lobe (odor hallucinations are most common)
- Fever, especially in children and the elderly
- Mental disorders, such as schizophrenia and psychotic depression
- Sensory problem, such as blindness or deafness
- Severe illness, including liver failure, kidney failure, HIV/AIDS, and brain cancer
When to Contact a Medical Professional
A person who begins to hallucinate and is detached from reality should get checked by a health care professional right away. Many medical and mental conditions that can cause hallucinations may quickly become emergencies. The person should not be left alone.
Call the health care provider, go to the emergency room, or call the local emergency number (such as 911).
A person who smells odors not present in his surroundings should also be evaluated by a health care professional. These hallucinations may be caused by a serious underlying medical condition.
What to Expect at Your Office Visit
The health care provider will do a physical examination and take a medical history. The person will be asked about the hallucinations. For example, how long the hallucinations have been happening, when they occur, or whether the person has been taking medications or using alcohol or illegal drugs.
Blood may be drawn for testing.
American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Arlington, Va: American Psychiatric Publishing. 2013.
Freudenriech O, Weiss AP, Goff DC. Psychosis and schizophrenia. In: Stern TA, Rosenbaum JF, Fava M, Biederman J, Rauch SL, eds. Massachusetts General Hospital Comprehensive Clinical Psychiatry. 1st ed. Philadelphia, Pa: Elsevier Mosby; 2008:chap 28.
Hockberger RS, Richards JR. Thought disorders. In: Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, Pa: Elsevier Mosby; 2013:chap 110.
Reviewed By: Fred K. Berger, MD, Addiction and Forensic Psychiatrist, Scripps Memorial Hospital, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.