A temporary lactase deficiency sometimes follows a stomach virus in children. When the child has diarrhea with the stomach virus, his or her intestines are stripped of the enzyme lactase. The child then has trouble digesting lactose when he or she drinks milk products. This produces watery diarrhea. This condition is only temporary.
Lactose intolerance is caused by a lack of lactase.
In young children, temporary lactose intolerance may follow a stomach virus. Persons can prevent the symptoms by avoiding foods high in milk content. Lactose may be better tolerated if it is eaten with other foods. In most cases, such tests are not required. If a person's symptoms are felt to be due to lactose intolerance, then milk and milk products can be eliminated from the diet for a period of time.