The most common causes of noninfectious chronic diarrhea are food intolerances, and IBS is often triggered by certain foods. Log your food intake to help identify triggers. Common triggers to look for are dairy, wheat, beef, and soy sensitivities. Also write down days when you feel particularly stressed, as anxiety can also be a trigger for IBS. Knowing what is most likely to cause a flare up can help you reduce your symptoms in the future.