Medical conditions, such as lactose intolerance and food allergies, are possible causes of chronic loose stool, according to the International Foundation for Functional Gastrointestinal Disorders. However, the condition is often caused by excess consumption of fructose, caffeine, artificial sweeteners and laxatives as well as medications and intestinal parasites.
Loose stool, called diarrhea by doctors, that is not accompanied by other symptoms, such as bleeding, is usually caused by excess consumption of a substance, notes the IFFGD. The artificial sweeteners sorbitol and mannitol, often found in diet gums and candies, are known laxatives when taken in excess. Herbal medicines such as senna tea may contain laxatives, which can be a cause of chronic diarrhea. Regular medicines may also contain substances that cause diarrhea, including misoprostol, stool softeners, alcohol and caffeine.
Lactose intolerance occurs when undigested lactose sugars ferment in the colon, explains the National Institute of Diabetes and Digestive and Kidney Disorders. The condition is caused by lactase deficiency, which is when a person does not have enough enzymes to digest lactose, or lactose malabsorption, which can be caused by lactase deficiency. Patients with lactose intolerance experience symptoms after eating foods containing lactose, including bloating, abdominal pain and gas.
The most common food allergens include fruit and vegetable pollen, peanuts, tree nuts and seafood, according to the American College of Allergy, Asthma and Immunology. Symptoms of food allergies include stomach cramps, wheezing, weak pulse, shortness of breath and anaphylaxis, a life-threatening condition.