• Parasites, such as Cryptosporidium parvum, Cyclospora cayetanensis, Entamoeba histolytica, Giardia lamblia, and microsporidia
• Bacteria, such as Campylobacter, Clostridium difficile, Escherichia coli (E. coli), Listeria monocytogenes, Salmonella enteritidis, and Shigella
• Viral infections, such as HIV, rotavirus, Norwalk agent, herpes simplex virus, and viral hepatitis
• Fungal infection, such as Candida overgrowth³

Diarrhea not resulting from an infection may be caused by:

• Antacids, laxatives, or supplements containing poor-quality magnesium
• Antiarrythmic drugs
• Antibiotics
• Antihypertensive drugs
• Caffeine addiction/withdrawal⁴
• Cancer drugs
• Diabetes, thyroid, and other endocrine/hormone diseases
• Flouride toxicity³
• Food additives (sorbitol, fructose, and others)
• Food allergies (usually lactose)
• Heredity – Certain diseases occur more often in related family members
• General gastric irritation
• Malabsorption – Inability to absorb nutrients through the lining of the gut into the bloodstream
• Medications for high blood pressure
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
• Previous surgery or radiation of the abdomen or gastrointestinal tract
• Reduced blood flow to the intestine
• Tumors
• Eating contaminated food and water while traveling 

The consistency of the stool can also indicate the cause of diarrhea:

• Oily or fatty diarrhea can be triggered by maldigestion or malabsorption syndromes. Chronic pancreatitis is a cause of pancreatic insufficiency, which leads to maldigestion and fatty stools. However, biliary tract obstruction, cholestatic liver disease, and bacterial overgrowth can also lead to maldigestion problems.³
• Watery diarrhea has many possible causes including carbohydrate malabsorption such as lactose, sorbitol, and fructose intolerance, or intestinal infections.³ 

Additional Information about Diarrhea

1. Diarrhea Overview
2. Common symptoms of diarrhea
3. Help me choose a natural and alternative treatment for diarrhea
4. Dietary and lifestyle recommendations that may help in the treatment of diarrhea
5. Conventional or prescription medications used in the treatment of diarrhea
6. Cited Sources and Additional Reading for diarrhea