Crohn's usually happens in the lower end of your small intestine and the beginning of your large intestine, or colon. But it can start anywhere in your digestive system, including the esophagus, stomach, and even the mouth. This makes it different from ulcerative colitis, which only affects your colon.
Your symptoms depend on where Crohn's is in your digestive tract. The disease can also affect other parts of your body, like your skin, eyes, joints, and liver.