The blackening of the first knuckle of the baby’s finger may be related to trauma, or there may be diseases such as skin eczema. 1. Trauma, if the baby finger by external impact, may lead to blood circulation in the hand is affected, blood flow stagnation, so this symptom may appear. 2. Skin eczema, due to skin irritation may lead to changes in the state of the skin, eczema, can lead to hyperpigmentation, will be accompanied by finger color changes, resulting in black. The first section of the baby’s finger black may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.