It is well known among those individuals who have been diagnosed with Chrohn's Disease, as well as their family and their doctors, that there is no known cause of Crohn's Disease. Even so, there are many theories as to what triggers the disease, although they are just theories, and have not been adequately proven at this point.

One of the most common theories on the cause of Crohn's Disease has to do with the reaction of the body's immune system to certain viruses. The theory is that the immune system reacts to a virus or bacteria within the digestive system. Some evidence shows that the body protects itself from a perceived threat to the digestive system by causing inflammation within the intestines. Those who suffer from inflammatory bowel diseases such as Crohn's Diseas and Ulcerative colitis do typically show a high instance of abnormalities in their immune systems. Doctors, however cannot confirm at this time whether the immune system abnormalities are a cause of the diseases, or a result of them.

There are a number of other factors that may figure strongly in the role of the development of Crohn's Disease. Infection, family medical history, genetics, diet, immunological factors, measles, MMR vaccine, and psychological factors all may all play a role in the development of Crohn's Disease. Some people develop Crohn's Disease after suffering gastroenteritis, yet the infection itself is not regarded as a cause of Crohn's Disease.

There have been studies that show that genetics may play a role in the cause of Crohn's Disease. Statistics show that if one member of the family suffers from Crohn's Disease, then there is an increased chance for other family members to develop the disease as well. First degree relatives, that is, parents, siblings, or children of an individual with any Inflammatory Bowel Disease will have a much higher risk of developing such Crohn's or other Inflammatory Bowel Diseases. The risk of developing Crohn's Disease is increased with identical twins.

Diet is another area that is looked at as a cause of Crohn's Disease, since it is often used by patients to address the symptoms of Crohn's Disease, and dietary changes will be inexpensive. Treatments involving an individual's diet vary in their results, but there is a consensus that certain foods should be avoided. Even though a particular diet doesn't cause Crohn's Disease in and of itself, there may be certain foods in the diet may trigger symptoms of Crohn's or make the symptoms worse.

Some vaccines, particularly measles and MMR vaccines have been looked at recently regarding a link between the vaccines and various diseases including Crohn's. There is not enough evidence, however to link these vaccines to Crohn's disease.

Psychological factors are not the cause of an Inflammatory Bowel Disease such as Crohn's disease and that there is no hard proof to support the link between those psycholigical factors and the disease itself. However, the stress of living with such a disease can make the symptoms of Crohn's Disease worse.