What causes ulcerative colitis?
Ulcerative colitis may be caused by a combination of:
But even the experts aren't sure what causes ulcerative colitis.
Genes
About 1 in every 5 people (20%) with ulcerative colitis has at least 1 close blood relative who has either the same disease or the closely related Crohn's disease. That's why it's believed that the genes people are born with may increase their chances of developing ulcerative colitis. In other words, the disease seems to "run in the family."
Immune system
In every person who has ulcerative colitis, the immune system, which is supposed to protect us from disease, doesn't quite work right. It's possible that ulcerative colitis begins when a microbe, such as a virus or bacterium, attacks the digestive tract. When the body's immune system tries to fight the microbe, the colon becomes inflamed. Or it may be that the inflammation is triggered by the microbe itself.
Living conditions
Ulcerative colitis is most common in industrialized countries with air pollution and occurs more frequently in cities than in rural areas. Therefore, where people live may partly determine whether they develop the disease.
Stress, food, and smoking
Stress and negative reactions (sensitivity) to specific foods used to be considered possible causes of ulcerative colitis. Experts now believe that stress and food sensitivity can make the symptoms of ulcerative colitis worse, but they don't cause the disease. Surprisingly, doctors believe that smoking cigarettes keeps people from getting ulcerative colitis. People who have never smoked and former smokers get ulcerative colitis, but current smokers do not.
Next: How can I tell if I have ulcerative colitis?