Different types of colitis have different causes:

• Infectious colitis is caused by a viral, parasitic or bacterial infection. Salmonella and E. coli are common causes. Most people get it from eating or drinking contaminated food or water.

• Pseudomembranous colitis. This type of colitis is usually caused by a specific bacterium known as C. diff (clostridioides difficile).

• Allergic colitis. Allergic colitis affects breastfeeding babies. It is caused by food intolerance, often to dairy milk (lactose intolerance) or soy milk (soy allergy). Proteins that breastfeeding people eat reach their babies through their breastmilk.

• Ischemic colitis is a side effect of intestinal ischemic syndrome, which is when your intestines aren't getting enough blood supply. Ischemia is usually caused by a blockage in your blood vessels, such as ablood clot, | aneurysm or atherosclerosis (a buildup of plaque).

• Inflammatory bowel diseases (IBD) are a group of conditions that cause chronic inflammation in your colon. They include ulcerative colitis, microscopic colitis and Crohn's disease. These conditions don't have a direct cause. Doctors believe they are a type of autoimmune disease, which means they cause your immune system to malfunction and attack its own tissues. Autoimmune diseases appear to be partially genetic and triggered by environmental factors.

• Diversion colitis is a side effect that can occur in people who've had a colostomy. It happens in the part of your colon that's no longer being used. Doctors believe that diverting your poop away from that part of your bowel may deprive it of certain nutrients that the tissues need to stay healthy. It only causes symptoms in a small number of people.