The black crust on the nipple may be Montgomery’s nodule, or it may be caused by nipple inflammation, breast cancer and other diseases. 1. Montgomery’s Nodule: If black crusts appear on the nipple of a woman who is pregnant, Montgomery’s Nodule is most often considered, mainly because of the proliferation of breast follicles and lobules after pregnancy, and the breast gradually becomes bigger, and Montgomery’s Nodule is formed by the bulging of the opening of Montgomery’s Gland Ducts, which can secrete breast milk or other fluids. 2. Nipple Inflammation: This disease is mainly related to cracked nipples and bacterial infection. Common triggering factors include decreased body resistance, failure to wash the nipples in time after breastfeeding, incorrect breastfeeding posture and so on. The patient’s one or both nipples will appear red, swollen, painful, cracked and other symptoms, if the cracking is serious, there will be secretions, which can be manifested as black crusts on the nipples. 3. Breast cancer: the cause of this disease is not yet clear, but research has shown that it may be related to heredity, hormone abnormality, radiation treatment of chest, obesity, over-nutrition, excessive alcohol consumption and other factors. Symptoms are not obvious in the early stage, but with the further development of the disease, patients’ nipples and areolas will show symptoms such as itching, red patches, scabs, flaking, etc. Some patients have black scabs on their nipples. Black crusts on the nipple should also be considered as a result of nipple fluid condensation, patients need to go to the hospital in time to do a series of relevant examinations to clarify the cause of black crusts on the nipple.