Infection

• According to the NDDIC, infection can be caused by bacteria or a virus. Viruses that cause diarrhea include herpes, rotavirus and hepatitis. Bacterial infections that cause diarrhea include salmonella, E. Coli and other bacteria. Viral infections usually go away on their own, but serious bacterial infections that cause diarrhea for extended periods of time may require medical assistance.
  
  

Food

• Some people's stomachs are not equipped to properly digest certain foods. According to GI Care, common food triggers of diarrhea include hot peppers, lactose and fatty foods.
  
  

Medication

• According to GI Care, new medications, particularly prescriptions, can occasionally affect the digestive system and health bacteria in the stomach, resulting in diarrhea. The NDDIC lists blood pressure drugs, cancer treatments, antacid medication and antibiotics as the leading medications that cause diarrhea.
  
  

Stomach Diseases and Disorders

• Chronic stomach and intestinal disorders are common culprits for diarrhea, according to GI Care. GI Care lists cancer of the colon, ulcers, Crohn's disease and irritable bowel syndrome as diseases or conditions that cause diarrhea.
  
  

Chemicals and Laxatives

• According to GI Care, many people use chemical laxatives daily to stimulate bowel movements. Laxatives can cause diarrhea in many people whose systems aren't used to laxatives or in people who misuse them. Over-the-counter laxatives include magnesium (available in Maalox or Mylanta), Nature's Remedy and ex-lax. Sorbitol is a common artificial sweetener that is also a known laxative. People who ingest high levels of food sweetened with sorbitol may experience diarrhea.