Most infants and toddlers need to change milk formulas during the growth and development process, and maladjustment during the transfer usually occurs at the first or second meal. Since the gastrointestinal function of infants and toddlers is weak, and each child has a different degree of adaptation to formula milk, the process of changing formula milk may result in a rash, vomiting, diarrhea, constipation and so on. When a rash appears, it means that the child is allergic to the new formula and it is recommended to change the brand; if the child has slight constipation, diarrhea and other indigestion symptoms, oral probiotics can be taken to regulate the intestinal flora, and the symptoms can continue to switch to milk. Usually, it takes about 2 weeks to change milk, and it should be done gradually to avoid being too anxious. If the child still has obvious discomfort after 2 weeks, it is necessary to consider changing to another formula. As the transition from breast milk to formula or milk powder and the conversion of formula, a series of discomfort may occur in the process, so it is recommended that parents should not be too emotional and can wait and observe or add probiotics when the symptoms are not serious.