Hallucination is a kind of illusory perception, which refers to the patient’s ability to perceive the existence of an objective object when it does not exist. According to the different sensory organs, hallucinations can be divided into hallucinations of hearing, vision, smell, taste, touch, and visceral hallucinations. Hearing hallucinations are when the patient hears sounds out of thin air, such as the sound of human speech, shouting or animal sounds, or the sound of objects, and may be accompanied by some emotional experiences, such as nervousness, fear, dread, or anger. Visual hallucinations are when the patient can see images or things that do not exist, and are often associated with disorders of consciousness. Olfactory hallucinations are the ability to smell unpleasant odors, such as burning or other foul smells. Taste hallucinations are when the patient feels that something they eat has a strange taste. Tactile hallucination means that the patient may have some of these numbness and electricity sensations. Visceral hallucinations are when patients feel that their internal organs are twisted, broken, or feel like there are worms swimming around inside their skin.