Ulcerative colitis is a chronic, or long lasting, disease that causes inflammation—irritation or swelling—and sores called ulcers on the inner lining of the large intestine.

Ulcerative colitis is a chronic inflammatory disease of the gastrointestinal (GI) tract, called inflammatory bowel disease (IBD). Crohn’s disease and microscopic colitis are the other common IBDs.

Ulcerative colitis most often begins gradually and can become worse over time. Symptoms can be mild to severe. Most people have periods of remission (times when symptoms disappear) that can last for weeks or years. The goal of care is to keep people in remission long term.

Most people with ulcerative colitis receive care from a gastroenterologist, a doctor who specializes in digestive diseases.

What causes ulcerative colitis?

The exact cause of ulcerative colitis is unknown. Researchers believe the following factors may play a role in causing ulcerative colitis:

• overactive intestinal immune system
• genes
• environment

Overactive intestinal immune system. Scientists believe one cause of ulcerative colitis may be an abnormal immune reaction in the intestine. Normally, the immune system protects the body from infection by identifying and destroying bacteria, viruses, and other potentially harmful foreign substances. Researchers believe bacteria or viruses can mistakenly trigger the immune system to attack the inner lining of the large intestine. This immune system response causes the inflammation, leading to symptoms.

Genes. Ulcerative colitis sometimes runs in families. Research studies have shown that certain abnormal genes may appear in people with ulcerative colitis. However, researchers have not been able to show a clear link between the abnormal genes and ulcerative colitis.

Environment. Some studies suggest that certain things in the environment may increase the chance of a person getting ulcerative colitis, although the overall chance is low. Nonsteroidal anti-inflammatory drugs, antibiotics, and oral contraceptives may slightly increase the chance of developing ulcerative colitis. A high-fat diet may also slightly increase the chance of getting ulcerative colitis.

Some people believe eating certain foods, stress, or emotional distress can cause ulcerative colitis. Emotional distress does not seem to cause ulcerative colitis. A few studies suggest that stress may increase a person’s chance of having a flare-up of ulcerative colitis. Also, some people may find that certain foods can trigger or worsen symptoms.