Most breast abscesses occur as a complication of mastitis, which is a bacterial infection that causes the breast to become red and inflamed.

Mastitis usually affects breastfeeding women, but it can also sometimes occur in women who aren’t breastfeeding.

Women who smoke have an increased risk of developing non-breastfeeding mastitis – otherwise known as periductal mastitis.

Bacterial infection

Most abscesses are caused by bacterial infections. The most common bacteria that causes mastitis is Staphylococcus aureus.

The bacteria usually enter the breast through small cracks or breaks in the skin of the nipple, which can sometimes develop during breastfeeding.

Infections can also be caused by an overgrowth of bacteria that usually exist quite harmlessly within the milk ducts (the tiny tubes inside the breast that carry milk). An overgrowth of bacteria can occur if stagnant milk collects in a blocked milk duct.

When bacteria enter your body, your immune system (the body’s natural defence) tries to fight them off by sending white blood cells to the affected area. The white blood cells attack the bacteria, which causes some of the tissue at the site of the infection to die, creating a small, hollow pocket.

The pocket starts to fill with pus, forming an abscess. The pus contains a mixture of dead tissue, white blood cells and bacteria. As the infection progresses, the abscess may get bigger and more painful as more pus is produced.

A breast abscess is a painful collection of pus that forms in the breast.

Most abscesses develop just under the skin and are caused by a bacterial infection.

Breast abscesses are painful, swollen lumps that may also:

• be red
• feel hot
• cause the surrounding skin to swell
• cause a fever (high temperature)

What causes a breast abscess? 

Breast abscesses are often linked to mastitis – a condition that causes breast pain and swelling (inflammation), and usually affects women who are breastfeeding.

Infections can occur during breastfeeding if bacteria enter your breast tissue, or if the milk ducts (tiny tubes) become blocked. This can cause mastitis which, if not treated, can result in an abscess forming.

Women who aren’t breastfeeding can also develop mastitis if bacteria enter the milk ducts through a sore or cracked nipple, or a nipple piercing.

White blood cells are sent to attack the infection, which causes tissue at the site of the infection to die. This creates a small, hollow area that fills with pus (an abscess).

Read more about what causes breast abscesses.

When to visit your GP

See your GP if your breast is red and sore. If you have mastitis, antibiotics may be prescribed to treat the infection.

If your symptoms persist after taking antibiotics, your GP may refer you for an ultrasound scan, which will confirm whether you have a breast abscess. This type of scan uses high-frequency sound waves to create an image of the inside of your body.

Treating a breast abscess

A breast abscess will need to be drained. Small breast abscesses can be drained using a needle and syringe. If the abscess is large, a small incision may be needed to drain the pus.

For both procedures, a local anaesthetic will usually be given to numb the skin around the abscess so you don’t feel any pain or discomfort.

Read more about how breast abscesses are treated.

The Map of Medicine is used by doctors throughout the NHS to determine the best treatment options for their patients. NHS Choices offers everyone in England exclusive and free access to this cutting-edge internet resource, which lets you see exactly what your doctor sees.

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Map of Medicine: breast disease

You should visit your GP if your breast is red and painful.

A breast abscess is usually a complication of mastitis (inflammation of the breast).

If you have mastitis, you may be prescribed antibiotics to treat the infection. Go back to see your GP if your symptoms don’t improve after taking antibiotics. 

If your breast is still hard, red and painful after taking antibiotics, your GP may refer you to a specialist breast unit for further investigations.

A breast abscess diagnosis will usually be confirmed using an ultrasound scan. This type of scan uses high-frequency sound waves to create an image of the inside of your body.

Draining a breast abscess

Most abscesses can be successfully treated with antibiotics and needle drainage under local anaesthetic.

A local anaesthetic may be used to numb the area of skin surrounding the infected breast tissue.

Small abscesses can be drained using a needle and syringe. Ultrasound may be used to guide the needle into place.

In the past, an operation was often used to drain larger abscesses. However, as with smaller abscesses, ultrasound guided drainage is now commonly used.

Diagnosing breast problems

Always visit your GP if you notice any changes to your breasts, such as a breast lump or discharge (leaking fluid) from your nipples. In some cases, these types of symptoms could be a sign of breast cancer.

If you have a lump on your breast, you’ll be referred to a breast clinic for an assessment, which may include an ultrasound scan and a mammogram (breast X-ray).