Patients with nipple overflow are often seen in the clinic, and most of them have nervous expressions and are worried if they have some major disease in their breasts. Therefore, we would like to explain about nipple overflow so that you can have a proper understanding of this phenomenon to avoid excessive negative effects. There are generally bloody overflow, breast overflow, plasma overflow, and purulent overflow, just to name a few. The most common breast disease for bloody overflow and plasma overflow is intraductal papilloma. It is a benign disease, but has a certain rate of malignancy. Therefore, patients suspected of having intraductal papilloma should undergo further investigation, such as ductography or lactoscopy, for further surgical excision and treatment. Ultrasound or mammography can be an important reference. Purulent overflow is commonly seen in acute and chronic inflammation of the breast, such as acute suppurative mastitis, plasmacytoid mastitis. Acute suppurative mastitis is not difficult to diagnose based on the clinical manifestations of redness, swelling, heat and pain, as well as routine blood tests and ultrasound examinations. The clinician has to make further treatment based on these conditions.