As a rule of thumb, diarrhea is considered to be severe if a:

• Baby younger than 3 months of age has large stools every 1 to 2 hours for longer than 4 hours.
• Baby age 3 months through 6 months has large stools every 1 to 2 hours for longer than 8 hours.
• Child age 7 months through 11 years has 6 or more large, loose stools in 12 hours.

Every baby and child has different bowel habits. Your baby may have as many as 4 to 10 stools a day, or as few as 1 every 3 days. Many breast-fed babies will have a bowel movement with each feeding and sometimes between feedings.

Formula-fed babies who have an intolerance to milk will have loose, green, watery stools, or they may have hard stools. Allergies to milk usually show up after the first few weeks of life.

Because the body loses large amounts of fluid quickly when severe diarrhea is present, your child has an increased risk for dehydration. If vomiting is also present, your child's risk for dehydration is even greater. When severe diarrhea is present, it is important to make sure that your child is taking enough fluids to prevent dehydration. Use an oral rehydration solution (ORS) and allow your child to drink as much fluid as he or she wants. Small amounts at frequent intervals are usually better tolerated. Replace any additional fluid lost through diarrhea or vomiting.

Your child's diarrhea may be foul-smelling (smell like rotten eggs) or yellow or green in color. There are many causes for these unusual changes, including bacterial, viral, or parasitic infections; cystic fibrosis; and celiac disease.