Crohn’s disease has no known cause, but doctors and researchers have linked the condition to the body’s immune system response. Diet may affect the symptoms of Crohn’s disease, but research has not found a connection between what you eat and the onset of Crohn’s disease.

Abnormal Immune System Response

Inflammatory bowel diseases may be the result of an abnormal response by your body’s immune system to normal, healthy bacteria. Doctors think the immune systems of people with Crohn’s disease mistake normal bacteria, foods, and otherwise-safe substances in the intestine as foreign intruders. The immune system responds by attacking and sending out white blood cells to remove the bacteria. But unlike healthy immune system, the immune system of a person with Crohn’s disease never turns off—it stays in a constant state of heightened activity. The accumulation of white blood cells over time causes the intestines to swell and become inflamed.


Proteins expressed by pathogens like bacteria and viruses may also have a role in the onset of IBD. Specifically, they may generate an abnormal response in the immune system.


Genetics may play a role in the development of Crohn’s disease. You may be more likely to develop the condition if a close family member has it. Recent research has identified several genes that may play an important role in determining how the body responds to foreign bacteria.


Smoking increases your risk for the disease.

View other Crohn's Disease Risk Factors.