Nipple discharge is any fluid that comes from the nipple when a woman is not breastfeeding. It is a fairly common experience and is most often caused by a harmless condition. The fluid can vary in color and consistency, appearing milky, yellow, green, clear, or bloodstained, and it may come from one or both breasts. The significance of nipple discharge depends largely on its characteristics and on whether it appears on its own or together with other changes. Discharge that occurs only when the breast or nipple is squeezed is usually less concerning than fluid that leaks on its own.
Causes and Risk Factors of Nipple Discharge
Most nipple discharge has a benign cause. Possible causes include:
- Hormonal changes, which can produce a milky discharge from both breasts and are sometimes triggered by certain medications or by conditions that raise a hormone called prolactin.
- Fibrocystic changes, which are normal variations in breast tissue and can cause green or yellow discharge.
- An intraductal papilloma, a small benign growth inside a milk duct that often causes clear or bloody discharge from a single duct.
- Infection, or a condition called duct ectasia in which a milk duct widens and becomes blocked.
- Breast cancer, which is a less common cause.
Certain features make discharge more concerning, including when it comes from one breast only, arises from a single duct, occurs without squeezing, or is bloody or clear — particularly when it is accompanied by a lump.
When to Seek Medical Care
Medical evaluation is recommended for nipple discharge that has any worrying features. These include discharge that is bloody or clear, that comes from only one breast or a single duct, or that appears spontaneously without the nipple being squeezed. Discharge that occurs together with a breast lump or with changes in the skin or the nipple should be assessed promptly. Any nipple discharge in a man should also be checked. Although the majority of cases turn out to be benign, a professional evaluation can identify the cause and ensure that any condition needing treatment is found early.