Bleeding, swelling and pain in the nipple are mainly considered to be related to external injury, mastitis, foreign body irritation, excessive milk and so on. 1. External injury: The nipple has been impacted by external force, or bitten by infants and children during breastfeeding, which can lead to nipple congestion, swelling and pain. 2. Nipple inflammation: it can lead to nipple swelling, hardness and pain, and if the condition is serious, bleeding and pus can also occur. 3. Foreign body irritation: excessive application of ethanol desiccant, soap and other items on the nipple can cause strong stimulation of the nipple, leading to nipple cracking, and then nipple bleeding, swelling and pain and other symptoms. 4. Excessive milk: Breastfeeding women’s excessive secretion of milk, overflow erosion of the nipple and surrounding tissues, can also trigger nipple cracking, and then bleeding, swelling and pain and other symptoms. At the same time, breast cancer, skin diseases around the nipple can also cause nipple bleeding, swelling and pain. Bleeding, swelling and pain in the nipple may also be related to other factors. Patients are advised to pay attention to the problem, seek medical advice as soon as possible, and take appropriate medical measures to intervene under the guidance of the doctor.