Explanation

Crohn's disease is an autoimmune disease. No one knows what triggers it though! The white blood cells of your immune system get confused between what's a foreign invader or germ and what's part of you, and they start attacking your gastrointestinal system.

Although Crohn's disease may affect any part of your gastrointestinal system, it mainly only attacks your small and large intestine. Crohn's colitis only affects your large intestine, Crohn's ileitis only affects your ileum, and IleocolicCrohn's disease affects both your ileum and large intestine.