Nipple overflow with yellow water may be caused by nipple infection, breast hyperplasia, cystic dilatation of milk ducts and other diseases. 1. Nipple infection: when bacteria infect the nipple, it may lead to nipple congestion and edema, showing acute inflammatory changes, which can be seen as redness and swelling of the nipple and surrounding tissues, with yellowish tissue fluid oozing out. 2. Mammary hyperplasia: mostly seen in women of childbearing age, the clinical symptom is cycle-like pain in the breast, accompanied by bead-like hyperplasia-like nodule formation, resulting in nipple overflow with symptoms of yellow water. 3. Cystic dilatation of breast ducts: in the early stage of the disease, there will be yellow nipple overflow, mostly intermittent. As the disease progresses, purulent discharge and localized lumps may appear. When there is nipple overflow with yellow water, you should go to the regular hospital for consultation, after clarifying the cause of the disease, and actively cooperate with the specialist for treatment.