Lactase is only needed when the baby is lactase intolerant, lactase intolerance is manifested by thin stools, recurrent eczema, etc. Currently, you can go to the hospital for lactase tolerance test, if there is intolerance to give oral and more common in breast-fed children, because the lactose contained in breast milk is higher. In addition to thin stools, babies with lactase intolerance generally have normal physical development and do not show symptoms such as loss of appetite and depression. If the number of stools increases significantly, more than 5-6 times a day and accompanied by dehydration such as reduced urine volume, dry mouth and lips, and few tears when crying, it is necessary to pay attention to the possibility of viral infections that require prompt medical attention.