Diarrhea is an increase in the number of stools per day and / or an increase in the looseness of stools. Diarrhea is a common problem that usually only lasts a few days. Diarrhea that lasts less than one week is called "acute."

Acute diarrhea can occur at any time of the year, but is most common during the winter months. Children less than 3 years old have an average of one to three episodes of acute diarrhea every year.