Generally speaking, the causes of blue buttocks in infants mainly include the following situations. The first is due to children suffering from birthmarks, when infants suffer from birthmarks, they will often have blue buttocks, which is caused by the anomalies of melanocytes to the skin surface of infants, generally no special treatment is needed, most infants with this kind of buttocks blue, will slowly disappear before six weeks of age. The second symptom is caused by trauma to the infant’s buttocks. If the infant’s local skin is traumatized, it will also cause bruising, which requires timely application of safflower oil for local topical application.