• Diarrhea is the sudden increase in the frequency and looseness of stools
• The main risk of diarrhea is dehydration
• Loose or runny stools do not cause dehydration
• Frequent, watery stools can cause dehydration

Causes

• Viral gastroenteritis (viral infection of the stomach and intestines) is the usual cause
• Bacteria (e.g., Salmonella or Shigella) cause some diarrhea. The main food-borne bacteria are Campylobacter, Salmonella and E.coli.
• Food-poisoning: Rapid onset of vomiting and diarrhea within hours after eating a food contaminated with toxins (e.g. cream dishes that are not properly refrigerated). The symptoms usually resolve in less than 24 hours without a need for medical care.
• Giardia (a parasite) occasionally, especially in child care centers

Dehydration: How to Recognize

• Dehydration means that the body has lost excessive fluids, usually from vomiting and/or diarrhea. An associated weight loss of more than 3% is required. In general, mild diarrhea, mild vomiting or a mild decrease in fluid intake does not cause dehydration.
• Dehydration is the most important complication of diarrhea.
• The following are signs of dehydration:
• Decreased urination (no urine in more than 8 hours) occurs early in the process of dehydration. So does a dark yellow, concentrated yellow. If the urine is light straw colored, your child is not dehydrated.
• Dry tongue and inside of the mouth. Dry lips are not helpful.
• Dry eyes with decreased or absent tears
• In infants, a depressed or sunken soft spot
• Delayed capillary refill longer than 2 seconds. This refers to the return of a pink color to the thumbnail after you press it and make it pale. Ask your doctor to teach you how to do this test.
• Irritable, tired out or acting ill. If your child is alert, happy and playful, he or she is not dehydrated.
• A child with severe dehydration becomes too weak to stand or very dizzy if tries to stand.

Definition of Diarrhea in Breastfed Infants

• The stools of a breastfed infant are normal unless they contain mucus or blood or develop a new bad odor.
• The looseness (normally runny and seedy), color (normally yellow) and frequency of stools (normally more than 6/day) are not much help.  Breastfed babies may normally even pass some green stools surrounded by a water ring (normal bile can come out green if intestinal transit time is rapid enough). 
• During the first 1 to 2 months of life, the breastfed baby may normally pass a stool after each feeding.  (However, if an infant's stools abruptly increase in number and looseness and persist for 3 or more stools, the baby probably has diarrhea.) 
• Other clues to diarrhea are poor eating, acting sick, or a fever.

Definition of Diarrhea in Formula-Fed Infants

• Formula-fed babies pass 1 to 8 stools per day during the first week, then 1 to 4 per day until 2 months of age. 
• The stools are yellow in color and peanut butter in consistency. 
• Formula-fed newborns have true diarrhea if the stools abruptly increase in number or looseness and persist for 3 or more stools, become watery or very runny, contain mucus or blood or develop a new bad odor. 
• Other clues to diarrhea are poor eating, acting sick or a fever. 
• After 2 months of age, most infants pass 1 or 2 stools per day (or 1 every other day) and no longer appear to have mild diarrhea.

Return to School

• Your child can return to child care or school after the stools are formed and the fever is gone.  The school-aged child can return if the diarrhea is mild and the child has good control over loose stools.