A milky discharge from a woman’s nipples during pregnancy and breastfeeding is normal and expected. A nipple discharge in a non-pregnant, non-lactating woman is abnormal, although quite common in women.
There are 15 to 20 milk ducts opening onto each nipple, and an abnormal discharge can come from one or more of these ducts. It may appear without squeezing, be from one or both sides, and may be clear, yellow, milky, brown, green or bloodstained in appearance.
Abnormal nipple discharge occurring in otherwise healthy breasts is known as “physiological discharge”. This does not usually require treatment. However, any abnormal nipple discharge should first be investigated by a doctor to rule out any underlying disease.
Some of the other causes include:
Duct ectasia is a benign condition caused by the enlargement of the milk ducts due to inflammation in the walls of the ducts. It usually occurs in women after menopause, and typically affects both breasts.
Duct papilloma is a growth in the milk duct that is usually benign. Treatment is by means of surgical removal.
Nipple eczema is an inflammatory condition affecting the skin of the nipple. In severe cases it may cause a weeping crusty nipple discharge.
Abnormal nipple discharge may be a late manifestation of breast cancer. Usually other signs like a lump in the breast or an inverted nipple will be visible long before a discharge appears.
Pagets Disease of the Nipple
Pagets disease is a benign (non-cancerous) breast tumor, involving the milk ducts. It usually causes a bloodstained nipple discharge.
Prolactin is the hormone responsible for stimulating milk production. Abnormal secretion of prolactin may occur in the presence of diseases of the pituitary or thyroid glands. Certain drugs or hormone therapies may also raise prolactin levels. These can include oral contraceptives and some stimulant drugs like cocaine.
Nipple Discharge in Men
A nipple discharge in men is usually related to something serious like breast cancer and should always be investigated.