In the vast majority of cases, secondary lactose intolerance recovers slowly 4-6 weeks after its onset. Most of the causes of secondary lactose intolerance are due to enteroviruses such as rotavirus or norovirus. When these enteroviruses attack the intestinal tract of children, they cause a temporary decrease in lactase activity in the intestine, resulting in secondary lactose intolerance in children. After the onset of secondary lactose intolerance, children will have more frequent and watery stools, which may even lead to dehydration and electrolyte disorders in children. In this case, oral rehydration salts can be used to replenish water and electrolytes, and lactase activity will be slowly restored when the viral infection improves.