The cause of sudden deafness is currently unknown. The main doctrines are viral infection, inner ear blood supply disorders, immunological factors and other causes. 1. Viral infection: Viral infection is one of the most common causes of sudden deafness, when the virus invades the inner ear through the blood. When the virus invades the inner ear through the bloodstream, the meninges, and the round window pathway, it may cause the symptoms of sudden deafness to occur. 2. Disorders of blood supply to the inner ear: The main function of the inner ear is to maintain the body’s hearing and balance. When the blood vessels in the inner ear become spasmodic or embolized, the blood supply to the inner ear will be impaired, resulting in sudden deafness. 3. Immunological factors: the decrease of some immune antibodies in the serum suggests that immunological factors may be involved in the occurrence of sudden deafness. Therefore, if the patient has the symptoms of sudden deafness, he should go to the hospital in time, to clarify the cause of the disease, so as to target the treatment.