If there is a change in frequency and characteristics of a child’s stool compared to usual, it could indicate the occurrence of diarrhea. Diarrhea can be classified into: 1. Acute diarrhea, which lasts for up to two weeks. 2. Persistent diarrhea, lasting between two weeks and two months. 3. Chronic diarrhea, lasting for more than two months. Based on the severity, it can be divided into: 1. Mild, generally without dehydration, electrolyte imbalances, or acid-base imbalances. 2. Moderate, accompanied by mild to moderate dehydration, or mild electrolyte disturbance. More severe cases involve severe dehydration and obvious symptoms of acid-base imbalance. Symptoms in children include lethargy, irritability, drowsiness, pale complexion, no fever, and a significant increase in white blood cell count. Causes of diarrhea can be divided into: infectious diarrhea, caused by viruses, bacteria, fungi, etc., and non-infectious diarrhea, including foodborne diarrhea, symptomatic diarrhea, allergic diarrhea, and other types of diarrhea.