Hallucinations are sensations that appear real but are created by your mind. They can affect all five of your senses. For example, you might hear a voice that no one else in the room can hear or see an image that is not real. These symptoms may be caused by mental illness, the side effects of medications, or physical illnesses like epilepsy or alcoholism. Depending on the cause, you may need to visit a psychiatrist, a neurologist, or a general practitioner.