Abnormally frequent or watery stools. Anything that increases the speed with which food and secretions pass through the bowel can cause diarrhea. Anytime the normal bowel transit time is shortened the bowels do not have sufficient time to absorb water from the stool and watery stools occur. Infections, allergies, lactase deficiency and other intestinal problems increase the speed with which food and secretions pass through the intestinal tract. The stools of newborn infants, especially those who are breastfed, are more watery than those of older infants.
Diarrhea in a small infant can result in serious dehydration very quickly. Children with watery stools, vomiting, or reduced fluid intake are at risk of dehydration. Those with blood or mucous in their stool may also have serious problems and should be evaluated by their doctor. Over-the-counter medications to treat diarrhea should be avoided in children under age 2 years unless specifically recommended by the baby's doctor.