Lactose-free formula is generally required until the diarrhea symptoms are cured, depending on the condition of the child, and there are individual differences. Lactose-free milk powder refers to milk powder that does not contain lactose and is mainly used for babies who are intolerant to lactose. Lactose intolerance is mainly due to low lactase secretion, the body can not fully digest and decompose lactose, resulting in non-infectious diarrhea, common diarrhea can exceed 3 days. Secondly, lactose intolerance can also occur secondary to intestinal viral infections, such as rotavirus infection. In case of mild lactose intolerance, most babies can significantly improve their diarrhea symptoms after 2-3 days of drinking lactose-free milk powder; in case of lactose intolerance due to viral infections, they usually need to drink for about 2 weeks while actively treating the primary disease, and can resume normal diet after the disease is controlled. In addition, if the infant’s diarrhea symptoms are more serious, he/she should go to the hospital in time. When the condition is under control, the process of switching to milk powder should first be added in small amounts, then gradually increased, and finally added until the complete transition to normal milk powder, without the need to continue to eat lactose-free milk powder for a long time, so as not to affect the normal growth and development of the child.