Nipple Discharge: 7 Possible Causes (& What to Do)

Nipple discharge is fluid that comes out of one or both nipples. It may be clear, white, yellow, green, brown, bloody, or pus-like, depending on the cause.

Nipple discharge is often benign, especially when it comes from both breasts, appears only when the nipple is squeezed, and is not bloody. However, it can also be linked to breast duct problems, infection, hormone changes, or, less commonly, breast cancer.

Treatment for nipple discharge depends on the cause and may involve monitoring, avoiding nipple stimulation, antibiotics, hormone treatment, or surgery. Medical attention is important when the discharge is spontaneous, bloody, clear, comes from one breast only, comes from a single duct, or is linked to a lump, pain, skin changes, nipple inversion, fever, or persistent symptoms.

What causes nipple discharge?

The main causes of nipple discharge include:

1. Intraductal papilloma

An intraductal papilloma is a small, non-cancerous growth that forms inside a milk duct, often close to the nipple. It is one of the most common causes of abnormal nipple discharge, especially when the fluid comes from one breast and one duct.

The discharge is often spontaneous, meaning it comes out without squeezing the nipple. It may be clear, watery, or bloody, and some people may also notice a small soft lump near the nipple or mild breast tenderness.

What to do: Treatment usually involves removing the affected duct through a small surgery, especially if the discharge continues or is bothersome. This can help stop the discharge and confirm that there is no cancer. In mild cases with clearly benign test results, the doctor may recommend close follow-up instead of immediate surgery.

2. Mammary duct ectasia

Mammary duct ectasia happens when the milk ducts under the nipple become wider and thicker. This condition is benign and is more common around menopause or after menopause.

The nipple discharge is often thick and sticky, and it may be green, brown, or black. Other symptoms can include nipple pain, tenderness, a lump or thick area near the nipple, gradual nipple pulling inward, or repeated inflammation around the ducts.

What to do: Many cases only need monitoring because duct ectasia is benign and may improve on its own. If there is inflammation or an abscess, treatment may include antibiotics and drainage. Surgery to remove the affected ducts may be needed if symptoms keep coming back.

3. Periductal mastitis or subareolar breast abscess

Periductal mastitis is inflammation around the milk ducts near the nipple. It may lead to a subareolar abscess, which is a pocket of pus under or near the areola.

In this condition, nipple discharge is often pus-like, but it can also be bloody or clear. Breast pain, redness, swelling, a tender lump near the areola, and fever may also occur, especially if the infection is more severe.

What to do: Treatment usually involves antibiotics, which may be adjusted if a culture is done. If an abscess forms, it may need to be drained with a needle or a small cut. Stopping smoking is also important because smoking is linked to repeat infections, and recurrent cases may need duct surgery.

4. Galactorrhea due to high prolactin

Galactorrhea is milky nipple discharge that happens outside pregnancy or breastfeeding. It is often caused by high levels of prolactin, a hormone that helps control milk production.

The discharge is usually milky, non-bloody, and can come from both breasts and several ducts. Other symptoms may include irregular periods, missed periods, infertility, low sex drive, headaches, vision changes, or symptoms related to thyroid, kidney, or liver problems.

What to do: Treatment depends on the cause and may include stopping or changing a medication that raises prolactin, when this is possible. Thyroid disease or other underlying conditions should be treated when present. If a prolactin-producing pituitary tumor is found, medicines such as cabergoline or bromocriptine may be used, while surgery may be needed in resistant cases or when vision is affected.

5. Paget disease of the nipple

Paget disease of the nipple is a rare type of breast cancer that affects the skin of the nipple and areola. Nipple discharge may be one of the first signs, especially when it happens with lasting nipple skin changes.

The discharge can be clear, bloody, or yellow, and it usually affects one breast. Other symptoms may include itching, burning, pain, crusting, scaling, redness, a rash that does not improve with regular eczema treatment, nipple pulling inward, or a breast lump.

What to do: Treatment usually involves breast cancer surgery, which may include mastectomy or breast-conserving surgery with removal of the nipple and areola area. The lymph nodes may also need to be checked. Radiation therapy, chemotherapy, hormone therapy, or targeted therapy may be recommended depending on the cancer type and stage.

6. Breast carcinoma

Most breast cancers first appear as a lump, but nipple discharge can sometimes be the first or only symptom. This is more concerning when the discharge is spontaneous, affects one breast, comes from one duct, or is bloody or clear.

At first, there may be no other symptoms. Over time, a breast lump, nipple retraction, skin dimpling, skin thickening, or swollen lymph nodes in the armpit may appear.

What to do: Treatment depends on the type and stage of breast cancer. It may include surgery, such as lumpectomy or mastectomy, and lymph node evaluation. Radiation therapy, chemotherapy, hormone therapy, targeted therapy, and long-term oncology follow-up may also be needed.

7. Physiologic nipple discharge

Physiologic nipple discharge is not a disease, but it is very common. It is usually related to normal hormone changes, pregnancy, breastfeeding, the period after breastfeeding, or repeated nipple squeezing.

This type of discharge is usually non-bloody and may be white, yellow, or green. It often comes from both breasts, from more than one duct, and only appears when the nipple is pressed, with no breast lump, skin changes, fever, or other warning signs.

What to do: No medical or surgical treatment is usually needed if the discharge has a clearly benign pattern and there are no warning signs. Avoiding repeated nipple squeezing can help because stimulation can make the discharge continue. A medical evaluation may be recommended if the discharge changes, becomes spontaneous, becomes bloody, affects only one breast, or appears with other symptoms.