Usually, ulcerative colitis occurs between the ages of 20 and 30, but infants may be affected too. It affects men and women roughly equally. Risk factors include:

• Hereditary factors
• Intestinal barrier dysfunction
• Changes to the gut flora (microbiome)
• Environmental influences (stress, unbalanced diet)

Ulcerative colitis progresses in episodes. It alternates between symptomatic and symptom-free phases (remission). The most common symptoms include severe bloody diarrhoea and cramp-like pain (often in the left lower abdomen). The results of the frequent and bloody bowel movement can be anaemia, fatigue, exhaustion, weight loss and further symptoms of a general nutrient deficiency. 

Furthermore, ulcerative colitis increases the risk of subsequent and concomitant diseases. It may cause a dangerous dilation of the colon (megacolon); those affected are also at increased risk of infections and colon cancers. Whilst it tends to be more rare than with other diseases such as Crohn's disease, other regions of the body are also affected by concomitant diseases, e.g. the eyes, skin and joints.