Children with blue lips are likely to have weak skin, lack of oxygen or heart disease. 1. Weak skin: children’s skin is thin, and the facial subcutaneous capillaries are also very rich, capillary congestion will be through the skin, the lips appear blue. 2. Lack of oxygen: When diseases such as pneumonia are combined with respiratory obstruction, gas exchange is blocked by lack of oxygen, which can cause bluish color around the mouth. 3. Heart disease: children with atrial septal defect or ventricular septal defect and other heart diseases, blood circulation will be poor and the phenomenon of hypoxemia, there will be a blue around the mouth, you can go to the hospital to do cardiac ultrasound for a clear diagnosis. Children’s mouth around the blue, may also be seen in other causes, parents are recommended to take the child to the hospital, complete the relevant examination, timely professional treatment.