Factors that may increase your risk of developing Crohn's disease include:

• Having a family history of Crohn's disease. Your risk increases if an immediate family member, such as a parent, brother, or sister, has the disease.
• Smoking cigarettes.
• Having Ashkenazi Jewish ancestry.

Factors that may cause Crohn's disease symptoms to flare up include:

• Medicines.
• Infections.
• Hormonal changes.
• Lifestyle changes, including increased stress.
• Smoking.