If it is a baby milk powder, it is generally not recommended to give it to the baby again after one month of opening. After the baby milk powder is opened, it is not actually airtight state, may be damp, resulting in milk powder caking and breeding bacteria, especially in the warm environment is more likely to deteriorate. At present, most of the infant formula, in fact, are recommended to open within three weeks to eat, more than three weeks should be discarded, or can not be given to the baby to eat. There are also some milk powder brands that can be consumed within four weeks. After opening, the process of constantly accessing the formula to dispense milk may also bring dirt into the formula. If the time is too long, such a milk powder with milk is not safe, the baby’s gastrointestinal function and immune function is weak, easy to be attacked by bacteria and viruses appear diarrhea, nausea, constipation and other discomforts. Therefore, for infant milk powder, should not be taken after one month after opening, it is recommended to drink within one month. If the opened one month of the milk powder is in a cool, dry, light-proof environment sealed storage, adults can still continue to take.