Olfactory disorders are defined as partial or total decrease, loss or abnormality of olfactory function. The olfactory nerve is the nerve fiber that runs from the olfactory epithelium through the sieve plate to the olfactory bulb. The ability to smell is a characteristic of the olfactory cells in the nasal mucosa. Injury to the nasal mucosa, olfactory bulb, olfactory filament or central nervous system connections may affect the sense of smell. Clinical manifestations are hyposmia, olfactory loss, olfactory absence, olfactory inversion, phantom smell and increased sensitivity to olfactory stimuli. Etiology 1.Nasal mucosa, olfactory bulb and olfactory filament neuropathy cause decrease or loss of olfactory function; while injury to the central nervous system connections usually does not accompany any detectable loss of smell. 2. Olfactory loss occurs due to abnormalities in the occurrence of the olfactory nerve during the embryonic period. 3. Occasionally, temporal lobe lesions are accompanied by temporary or paroxysmal phantom sniffing. Loss of smell is often combined with taste impairment, depending on volatile substances in food and beverages. 4. The olfactory impairment caused by influenza is temporary. 5.Meningioma, metastasis or infiltrative tumor in the anterior cranial sulcus artery or frontal lobe may compress the olfactory bulb and olfactory bundle, leading to olfactory impairment. 6, In cranial trauma, the olfactory filaments of the olfactory nerve via the sieve plate may be torn, or the olfactory bulb may be torn (contusion). Patients with olfactory impairment usually will not affect their daily work and study. Patients with olfactory impairment should be further examined for the cause and treated for the right reason.