The research on the pathology of olfaction is still not thorough. Olfactory failure includes the following conditions: 1. Olfactory hyposmia or loss of smell, olfactory inversion or phantom smell. Olfactory hyposmia and loss of smell are easy to understand. Olfactory inversion may be something that people do not understand, such as smelling a stinky smell when there is clearly a scent. Phantom smell is when the place has no smell at all, but smells some kind of smell, for example, there is no scent at all, but smells like flower dew or other perfume. 2. For olfactory inversion and phantom smell, it is mainly based on some patients with psychosis and schizophrenia. 3. For hyposmia and loss of smell, clinical and neuritis, nasal diseases and central diseases need to be excluded.