Every day, we lose body fluids (water and other fluids) in urine, stool, sweat, and tears. We replace lost fluids by eating and drinking. Dehydration occurs when more fluid leaves the body than enters it. This can happen when a child does not drink enough fluids or when the body is sick and loses fluids through vomiting, diarrhea, and fever. Dehydration can happen slowly or quickly, depending on how the fluid is lost and the age of the child. Young children and infants are more susceptible to dehydration. In this article, we will provide useful information to help caregivers promptly recognize the symptoms of dehydration in children that need to be recognized early.