The cause of ulcerative colitis is unknown but it is defined as mild, moderate or severe according to the frequency of diarrhoea, the presence of blood and how generally unwell the person is. Different studies suggest that this and other inflammatory bowel diseases may result from an abnormal response by the body's immune system. The general symptoms of ulcerative colitis includes frequent watery diarrhoea, pain on opening the bowel, urgent and frequent need to open the bowel, the sensation of incomplete emptying the bowel, diarrhoea even during the night, nausea, loss of appetite, weight loss and extreme tiredness.