The common clinical causes of hard black objects in the belly button are the blood scabs formed by the healing of the umbilical cord stump, or the dirt left over from daily life. 1. Blood scabs formed by the healing of the umbilical cord stump: after the delivery of the fetus cut the umbilical cord, the umbilical cord stump will leave blood scabs or scars after healing, in this case, parents should not pick the corresponding parts, it is recommended to use warm water to wash it, after a period of time can be naturally fall off. 2. Residual dirt: some people do not pay attention to personal hygiene habits, and the navel area is relatively deep, this situation is easy to residual sweat and dirt, thus forming a black hard substance in the navel. It is recommended that the existence of the relevant situation of the crowd according to the situation for targeted treatment, if there is a corresponding part of the inflammation of the situation, it is recommended to go to the hospital surgical treatment.