Theories about what causes ulcerative colitis abound, but none have been proven.
The most popular theory is that the immune system reacts inappropriately to agents such as food components, viruses or bacteria within the bowel lumen, causing ongoing inflammation in the intestinal wall.
People with ulcerative colitis have abnormalities of the immune system, but doctors are unable to determine whether these abnormalities are the cause or the result of the disease.
The colitis is not caused by emotional distress or sensitivity to certain foods or food products, although these could trigger the symptoms.
While stress or new medications commonly make the symptoms worse, they have no role in the actual cause of the disease.
Affected people may possibly have an abnormal defense mechanism against the bacteria that are normally present in the gut.
Another aspect that might be significant is having a long-term reaction to a particular bacterium or virus.
Reviewed by Dr Ismail Moola, MBCHB (UCT) FCP (SA) Cert Gastro Phys (SA). Specialist Physician / Gastroenterologist, Netcare Sunninghill Hospital; Lecturer, Department of Internal Medicine, Division of Gastroenterology, University of the Witwatersrand.