A black spot on the tip of the nipple may be pigmentation, or it may be caused by breast eczema or clogged pores. A grain of black stuff on the nipple may simply be caused by melanin deposition, considering that the localization has been subjected to friction for a long time as well as sex hormone changes. It may also be caused by mammary eczema, when the condition flares up, there will be obvious itching, red rash and other symptoms, it is considered that the condition in the treatment did not pay attention to local hygiene or frequent scratching, so that the epidermal tissues of the melanin deposition caused. Of course, it can not be ruled out that the sebaceous glands at the nipple secrete too much oil, which can not be completely discharged to block the pores. There is also the possibility that the black stuff on the tip of the nipple may be a tumor and other reasons, when the above situation occurs, you can go to the hospital for examination, for the cause of the treatment.