Lactose-free milk powder refers to milk powder with lactose removed and can be taken for 3 days to relieve diarrhea. Lactose-free formula can reduce the digestive burden of the intestine and facilitate recovery from diarrhea, and is suitable for diarrhea caused by lactose intolerance or secondary lactose intolerance caused by intestinal viral infections such as rotavirus, norovirus and coxsackievirus infections. Children usually take it for 3 days to see the effect, and 1-2 weeks after the stools return to normal can be changed to ordinary formula feeding, usually for 2-4 weeks, but the specific time should be decided according to the severity of the child’s condition and comprehensive medication. In addition, children with lactose intolerance secondary to intestinal viral infection should be given lactose-free formula along with other treatments, including montelukast and probiotics on an empty stomach to regulate gastrointestinal function. Children with unrelieved diarrhea or recurrent diarrhea should go to the hospital for further examination.