Most cases of acute diarrhea go away without treatment. However, severe diarrhea (greater than 10 bowel movements a day or diarrhea where fluid losses are significantly greater than oral intake) can cause dehydration, which can be life-threatening if untreated. Dehydration is particularly dangerous in children, older adults and those with weakened immune systems.

Seek medical attention for a child with these symptoms:

• Diarrhea that doesn't improve after 24 hours.
• No wet diaper in three or more hours.
• A fever of more than 102 F (39 C).
• Bloody or black stools.
• A dry mouth or tongue or cries without tears.
• Unusually sleepy, drowsy, unresponsive or irritable.
• A sunken appearance to the abdomen, eyes or cheeks.
• Skin that doesn't flatten if pinched and released.

Schedule a doctor's visit for an adult with these symptoms:

• Diarrhea lasts more than two days without improvement.
• Excessive thirst, dry mouth or skin, little or no urination, severe weakness, dizziness or lightheadedness, or dark-colored urine, which could indicate dehydration.
• Severe abdominal or rectal pain.
• Bloody or black stools.
• A fever of more than 102 F (39 C).