Although frequent diarrhea is common among children, it can be difficult to determine exactly what's causing it.

Chronic diarrhea can have many causes, including:

• Bacterial or parasitic infection, which is a rare cause in developed countries
• Celiac disease — an immune reaction to eating gluten, a protein found in wheat, barley and rye
• Chronic inflammation of the digestive tract (inflammatory bowel disease), such as ulcerative colitis or Crohn's disease
• Chronic, nonspecific diarrhea of childhood — a condition that typically occurs in children ages 1 to 3 for which no cause can be found and which usually resolves on its own without causing weight loss or poor growth
• Dietary protein or sugar intolerance
• Irritable bowel syndrome

Rare causes of chronic diarrhea also include:

• Neuroendocrine tumors — tumors that typically start in the digestive tract
• Hirschsprung's disease — a condition present when a baby is born (congenital) that results from missing nerve cells in the muscles of part or all of the baby's colon
• Cystic fibrosis — an inherited disease that can lead to a buildup of thick mucus that prevents the body from absorbing nutrients from food
• Eosinophilic gastrointestinal disorders — a group of complex diseases characterized by higher than normal amounts of white blood cells, called eosinophils, in organs in the digestive system
• Zinc deficiency

In children, slower than normal growth or weight loss accompanying diarrhea may indicate that the stomach and intestine are having difficulty absorbing nutrients — common in cases of celiac disease or cystic fibrosis — while other problems may be more difficult to diagnose.

When to see a doctor

In children, particularly young children, diarrhea can sometimes lead to dehydration. This is especially true if the diarrhea is combined with a fever or vomiting or both. Call your doctor if your child's diarrhea doesn't improve after 24 hours or if your baby:

• Hasn't had a wet diaper in three or more hours
• Has a fever of more than 102 F (39 C)
• Has bloody or black stools
• Has a dry mouth or cries without tears
• Is unusually sleepy, drowsy, unresponsive or irritable
• Has a sunken appearance to the abdomen, eyes or cheeks
• Has skin that doesn't flatten if pinched and released