Crohn's disease is a complex disease and the exact cause remains unknown. Researchers believe that inherited genes, environmental factors and the immune system all play a role.

Various factors have been identified as possible causes of Crohn's disease but none has actually been proven definitively.

The most likely candidate is the involvement of a defect in our immune system or perhaps an overzealous response to an infection.

Our immune system is specially designed to make sure that we are protected from attack by infections or harmful toxins. Some of these infections or toxins are ingested with our food.

In the food we eat, as well as nutrients there are also poisons and infectious agents, such as bacteria and viruses, which our body cannot use so they need to be excreted.

These can cause damage to our health, so our immune system will trigger a protective inflammation as part of our normal defences.

Autoimmune diseases cause the immune system to function incorrectly, and this can cause the immune system to become overloaded.

The normal protective mechanisms that lead to the release of inflammatory mediators instead cause uncontrolled inflammation and damage to our own body tissues and organs. Many diseases are thought to have an autoimmune component to them, including multiple sclerosis, rheumatoid arthritis and lupus.

It is not certain what actually causes Crohn’s disease, but because of the inflammation damage in the gut associated with the disease, it is thought that it may be an autoimmune disorder.

No specific infection has yet been identified as an initial trigger for Crohn’s disease. But an infection may start the initial inflamed response that causes the disease.

The damaged intestine in Crohn’s often becomes infected with bacteria, but this is thought to be as a result of the disease. It does however make matters worse.

Crohn’s disease is not an infectious disease itself. It cannot be spread through contact with an individual who has the disease.

Smoking is not an initial trigger of disease and no specific dietary factor has been implicated as a cause.