Diarrhea is commonly caused by bacteria, viruses, or parasites. Inflammatory bowel diseases (IBD) including Crohn's disease and ulcerative colitis can cause chronic diarrhea.
Irritable Bowel Syndrome
Irritable bowel syndrome commonly causes abdominal pain, cramping, bloating, gas, food intolerance, diarrhea, constipation and altered bowel habits.
IBS is a chronicle condition. The exact cause of it is unknown and may be due to multiple factors. Most people with IBS do not have very severe symptoms and the symptoms are usually relieved by passing a bowel movement.