Possible causes of sudden onset (acute) diarrhea

Cause	Features	Treatment
Infectious diarrhea
Viral infection	Loose stool, low-grade fever, feel ill	None, usually resolves within 48 hours
Bacterial infection	Fever (temperature >101°F or 38.4°C), bloody stools	Usually none, antibiotics in selected situations
Parasite	Not common in developed countries, may be seen in returning traveler or camper	Antibiotics in most cases
Non-infectious diarrhea
Antibiotics	Loose stool begins after antibiotic started, usually resolves with a few days after stopped	Usually none
Food intolerance (eg, lactose intolerance)	Diarrhea, abdominal pain, and/or gas after consuming food	Determine if food intolerance is the cause
Inflammatory bowel disease (eg, Crohn's disease, ulcerative colitis)	Mouth sores, diarrhea, abdominal pain, weight loss, and fever	See a healthcare provider for full evaluation and treatment
Irritable bowel syndrome	Chronic lower abdominal pain, diarrhea and/or constipation	Symptomatic treatment
Celiac disease (gluten sensitivity)	None to diarrhea, weight loss, abdominal pain, gas	Complete avoidance of wheat, rye, barley

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