Nipple discharge: causes, red flags and when to seek help

The features of the discharge itself tell doctors a great deal. Fluid that appears from one nipple only, comes out spontaneously and stains clothing, is bloody or watery-clear, or comes from a single duct is treated more seriously than fluid from both nipples that appears only when pressed and is milky, green, brown or sticky.

Colour alone is not a reliable guide, so a doctor will usually test the fluid or arrange imaging if the pattern is the concerning type. Make a mental or written note of which side, whether it is spontaneous, the colour and whether there are any other breast changes.

Breast tissue contains many small ducts that can produce fluid in response to hormones, stimulation or changes in the duct lining. Common explanations include pregnancy and recent breastfeeding, which can leave a milk-like discharge for months, a benign growth within a duct (intraductal papilloma), widened ducts with age that produce sticky greenish or brown fluid, and infection or inflammation.

Raised levels of the hormone prolactin, from a small benign pituitary tumour or as a side effect of some medicines including certain antipsychotics and anti-sickness drugs, can cause milky leakage from both breasts, often with irregular periods. An underactive thyroid can also raise prolactin.

• Pregnancy, breastfeeding and the months after stopping.

• Vigorous nipple stimulation, tight bras or friction.

• Intraductal papilloma, a small wart-like growth in a milk duct.

• Duct ectasia, widening of ducts, more common near menopause.

• Medicines, including some antipsychotics, anti-sickness drugs and hormone treatments.

• Raised prolactin from the pituitary gland.

• Infection, such as mastitis or an abscess.

The NHS says mastitis is when the breast becomes swollen, hot and painful, is most common in breastfeeding women, and usually affects one breast with symptoms coming on quickly. They include a swollen area that may feel hot and painful and may be red though this is harder to see on black or brown skin, a wedge-shaped lump or hard area, a burning pain, and nipple discharge that may be white or contain streaks of blood, with flu-like symptoms. It advises seeing a GP if symptoms do not get better 12 to 24 hours after treating at home or 48 hours after antibiotics, or if you get mastitis and are not breastfeeding. It says smoking, nipple damage such as a piercing or eczema, a breast implant and a weakened immune system can cause it.

The NHS breast pain page says breast pain is usually linked to periods and that breast pain by itself is unlikely to be a symptom of cancer.

The NHS breast cancer symptoms page lists nipple discharge if you are not pregnant or breastfeeding, which may have blood in it, alongside a lump or swelling in the breast, chest or armpit, dimpling of the skin that may look or feel like orange peel, a change in the colour of the skin on the breast, a change in the size or shape of one or both breasts, and a change in the shape or look of the nipple such as turning inwards or a rash that may look like eczema. It says you can have these symptoms without pain and that breast pain by itself is not usually a symptom of breast cancer. It says to see a GP if you have a lump or swelling or any changes in your breasts or nipples that are not normal for you.

The NHS breast pain page says to ask for an urgent GP appointment or get help from NHS 111 if you have breast pain and a very high temperature or feel hot, cold or shivery, any part of your breast is red, hot or swollen, there is a hard lump that does not move around, you get nipple discharge which may be streaked with blood, one or both breasts change shape, the skin is dimpled, or you have a rash on or around the nipple or the nipple has sunk into the breast.

Bloody discharge from one nipple, a new lump, nipple inversion that is new, or discharge in a man should be assessed promptly even if there is no pain.

The NHS says the GP will ask about your symptoms, any breast screening you have had and whether anyone in your family has had breast cancer. If you have a lump or unusual changes they may ask to look at and examine your breasts. You will need to undress from the waist up behind a screen and can have a friend, family member or another member of staff in the room.

If the GP thinks symptoms could be cancer, you may be referred to a breast clinic, where assessment commonly includes clinical examination, imaging with mammography or breast ultrasound depending on age, and sometimes a needle biopsy or testing of the fluid. Other tests include blood prolactin and thyroid function if both breasts leak milk-like fluid.

Avoid squeezing or stimulating the nipple, since that can keep the discharge going and make assessment harder. Wear a soft, supportive bra, use breast pads if fluid stains clothes and keep the area clean. Note any other changes. The NHS encourages checking your breasts regularly so you know what is normal for you, which makes it easier to notice any changes in size, look or feel.