The cause of Crohn's disease is unknown. Studies suggest that this and other inflammatory bowel diseases may result from an abnormal response by the body's immune system to normal intestinal bacteria.¹ Disease-causing bacteria and viruses also may play a role in causing the condition.

Crohn's disease can run in families, so some people may be more likely than others to develop the condition when exposed to something that triggers an immune reaction. Environmental factors may also play a role in causing the disease.