Crohn refers to Crohn’s disease. The cause of this disease has not been fully clarified, and it may be related to factors such as heredity, environment, infection and immunity. 1. Heredity: Studies have shown that Crohn’s disease is a genetically heterogeneous disease, with a higher incidence in the first-degree relatives of its patients, but not all of them develop the disease, mainly as a result of the joint action of other factors such as the environment. 2. Environment: Environmental factors mainly play a role in genetically susceptible individuals, including smoking, high-fat diet, inappropriate lifestyle, social industrialization and so on. 3. Infection: pathogenic microorganisms such as Mycobacterium avium subspecies paratuberculosis or measles virus inclusion bodies have been clinically examined in the tissues of patients with Crohn’s disease, so it is thought that it may be related to abnormal immune response of the own intestinal flora. 4. Immunity: it is mostly considered to be caused by the abnormal activation of the immune response of the intestinal mucosa, which is also one of the direct causes of this disease. Patients with Crohn’s disease need to actively cooperate with the doctor’s treatment and strengthen the daily life management, so as not to delay the disease.