Ulcerative colitis is the abbreviation for chronic nonspecific ulcerative colitis, a chronic inflammatory disease of the rectum and colon of unknown origin. The main clinical manifestations are diarrhea, mucopurulent stools, abdominal pain and urgency. The disease varies in severity and is recurrent or prolonged with a chronic course. The disease can occur at any age, with 20-50 years old being the most common. There is no significant difference in the incidence between men and women. The disease is more common in Europe and the United States, but the incidence in China is low, and the disease is generally mild. The etiology and pathogenesis of the disease have not been fully elucidated. It is believed that the onset of the disease may be related to the following factors: i. Autoimmunity The disease is mostly complicated by nodular erythema, arthritis, uveitis, iritis and other autoimmune extraintestinal manifestations, adrenocorticotropic hormone treatment can make the disease remission, anti-colonic epithelial cell antibodies can be detected in the serum of some patients, so it is believed that the occurrence of the disease and autoimmune reaction may be related. There is information that during the active phase of ulcerative colitis, the mast cells of the intestinal wall increase, and the cells are stimulated to release a large amount of histamine, resulting in intestinal wall congestion, edema, smooth muscle spasm, mucosal erosion and ulceration, which is related to the acute onset or sudden relapse, is a rapid hypersensitivity reaction, and this allergic reaction of the intestinal wall may be a local manifestation of the disease. The incidence of this disease is high in the blood family, about 5-15% of the relatives of patients have this disease, and there are significant differences in the incidence between races, suggesting that genetic factors play a role in the development of the disease. The pathological changes and clinical manifestations of the disease are similar to those of infectious diseases of the colon, such as bacillary dysentery. Therefore, infection has long been considered as the cause of the disease, but so far it has not been possible to identify the causative bacteria, viruses or fungi. It has been suggested that depression and anxiety may be related to the occurrence and recurrence of the disease, but recent clinical data indicate that the disease is not more common in people with a history of psychiatric abnormalities or trauma than in the general population. In short, the occurrence of the disease may be the result of the interaction of immune, genetic and other factors and exogenous stimuli.