“Inflammatory bowel disease is a term that refers to Crohn’s disease and ulcerative colitis, two inflammatory conditions that affect as many as 1.6 million Americans, most diagnosed before age 35.

IBD is the common name used to describe two chronic diseases of the intestinal tract ― Crohn’s disease and ulcerative colitis ― that cause inflammation in the intestines:

• Crohn’s disease can affect any part of the gastrointestinal tract from the mouth to the anus.
• Ulcerative colitis can affect any part of the large intestine.
• A third category, indeterminate colitis inflammatory bowel disease, refers to IBD that has features of both Crohn’s disease and ulcerative colitis.

IBD is an autoimmune disorder, meaning the body’s immune system attacks healthy tissues. It is not yet known what triggers these attacks ― and why IBD develops in some people and not in others. However, researchers are working to understand more about the mechanisms behind the condition and the impact of genetic, environmental, infectious, immune and other factors, including the balance of bacteria in the gut.

IBD can affect people in any ethnic or racial group, but statistically, people of Jewish ancestry have a greater risk of developing inflammatory bowel disease. Environmental factors may contribute: IBD is rare in the southern hemisphere.   It also can run in families.”

John Hopkins Medicine (Inflammatory Bowel Disease (IBD) | Johns Hopkins Medicine)