There are black hard lumps in the belly button followed by white, may be localized dirt or navel infection, folliculitis and other causes. 1. localized dirt: if you do not pay attention to the navel area for a long time, the navel accumulates too much dirt, there may be a black hard lump in the navel behind the white situation. 2. Umbilicitis: When the navel area is infected by Staphylococcus aureus, it may induce umbilicitis, which may cause the navel area to appear red, swollen, increased secretions, and even produce a bad smell, if the secretions are not cleaned up in time, there may be a black hard lump in the navel, the back of the white situation. 3. Folliculitis: If the navel area is infected by inflammation, which leads to folliculitis, it will cause local melanin precipitation, there may be black hard lumps in the navel, behind the white situation, in addition to local pain. The belly button has a black hard lump behind the white need to go to the hospital to do the examination, according to the cause of the disease symptomatic treatment.