• Immune system: It's possible that a virus or bacterium may trigger Crohn's disease; however, scientists have yet to identify such a trigger. When your immune system tries to fight off the invading microorganism.
Heredity: Crohn's is more common in people who have family members with the disease, so genes may play a role in making people more susceptible. However, most people with Crohn's disease don't have a family history of the disease.
Risk factors:
• Age: Crohn's disease can occur at any age, but you're likely to develop the condition when you're young.
• Ethnicity: Although Crohn's disease can affect any ethnic group, whites have the highest risk, especially people of Eastern European (Ashkenazi) Jewish descent.
• Family history: You're at higher risk if you have a first-degree relative, such as a parent, sibling or child, with the disease.
• Cigarette smoking: Cigarette smoking is the most important controllable risk factor for developing Crohn's disease. Smoking also leads to more-severe disease and a greater risk of having surgery.
• Nonsteroidal anti-inflammatory medications: These include ibuprofen (Advil, Motrin IB, others), naproxen sodium (Aleve), diclofenac sodium and others. While they do not cause Crohn's disease, they can lead to inflammation of the bowel that makes Crohn's disease worse.
Courtesy: Mayo Clinic