Green lumps on the back of infants may be caused by Mongolian spots, hemangiomas, subcutaneous petechiae and so on. 1. Mongolian spots: gray-blue skin lesions appearing on the lumbosacral area and buttocks shortly after birth, usually caused by abnormal pigment formation or vascular malformation, etc. Generally, they grow slowly and do not have obvious pain, itching and other discomforts. If it grows on the back, it can lead to green lumps on the baby’s back. 2. Hemangioma: Hemangioma can be formed by abnormal proliferation of vascular cells during the embryonic period, and it often occurs in the head and neck, followed by the trunk and limbs. Superficial hemangioma is bright red at the beginning, and then the color gradually deepens and changes to dark purple; deep hemangioma can be manifested as skin surface elevation, showing normal color or translucent blue. It can also lead to blue lumps on the back of infants. 3. Subcutaneous petechiae: it can be caused by mechanical injury such as collision, drugs, infection, coagulation dysfunction, etc. It mainly manifests as greenish-purple petechiae with a diameter of more than 5 millimeters on the skin. It can also lead to bruises on the baby’s back. There are many other causes of bruises on the back of infants, which should be taken seriously, timely consultation, identification of the cause of the disease, and further treatment or treatment in accordance with medical advice.