The major causes of diarrhea are viral infections, bacterial infections, parasites and food intolerance, states Healthline. Antibiotics sometimes cause diarrhea because they destroy the natural balance of bacteria in the intestines, according to Mayo Clinic.
Bacterial infections that cause diarrhea include E. coli and Salmonella, explains the National Institute of Diabetes and Digestive and Kidney Diseases. Viral infections that cause diarrhea include rotavirus and viral hepatitis. Other causes of diarrhea include allergies to certain foods and diseases of the intestines, such as ulcerative colitis and Crohn's disease, explains WebMD. Gallbladder removal surgery and abdominal surgery also sometimes cause diarrhea, as stated by Mayo Clinic. People who travel to foreign countries may experience traveler's diarrhea after consuming contaminated food or water.