A breast abscess is a pus-filled lump that grows under the skin as a result of an infection. These abscesses usually form during breastfeeding, but anyone, regardless of sex, can develop one.

This article describes what a breast abscess is and explores the causes, symptoms, and treatments. It also looks at how to prevent the issue and when to see a doctor.

A breast abscess is a painful, pus-filled lump under the skin of the breast.

Breast abscesses can be a complication of mastitis, which is an infection of the breast.

These lumps are more common among females who are lactating. According to a 2020 summary of scientific literature, lactational mastitis occurs in 2–3% of lactating females, 5–11% of whom may develop one or more abscesses.

However, breast abscesses can form in anyone. According to a 2018 review, abscesses unrelated to lactation typically form in people with obesity and people who smoke.

As the authors of the 2018 review note, if a person does not receive treatment for mastitis, the infection can destroy tissue, allowing a sac to form beneath the skin and fill with pus. To the person, it may feel like a lump. This is a breast abscess.

Lactational breast abscesses typically occur due to an infection with Staphylococcus aureus and Streptococcal bacteria.

When lactation is not involved, a breast abscess commonly results from a mix of S. aureus, Streptococcal, and anaerobic bacteria — bacteria that do not grow where oxygen is present, in places such as the gut.

An infection in the breast can occur when:

  • bacteria enters through cracks in the nipple
  • a milk duct is clogged
  • foreign material enters the area, as with a nipple piercing or breast implant

If a person has developed a breast abscess, they may feel or notice a mass in the breast tissue along with symptoms of an infection of the breast. These symptoms may include:

  • low milk production
  • warmth in the area
  • pain in the breast
  • discharge from the nipple
  • flushed skin
  • a high temperature
  • a headache
  • nausea
  • vomiting
  • flu-like symptoms
  • fatigue

To diagnose a breast abscess, doctors typically ask questions about symptoms and perform a breast exam.

They may also request an ultrasound or take a biopsy of the fluid inside the lump.

Doctors may need to drain the fluid from the lump. They may extract the fluid with a needle or drain it by making a small cut in the skin.

Doctors typically use needle aspiration if the person is lactating or if the mass is smaller than 3 centimeters.

For people who develop these abscesses and are not lactating, there is a higher rate of the abscesses reoccurring, so a person may have to have more than one extraction or drainage.

If the drained abscess leaves a large cavity, a healthcare professional will need to pack it, to help drainage and healing.

Also, the doctor may prescribe a course of antibiotics for 4–7 days.

Over-the-counter drugs, such as acetaminophen or ibuprofen, can help relieve the pain. A person can also use a warm compress to soothe inflammation.

Applying a moisturizer to the nipples can help keep them from cracking and providing a way for bacteria to enter the body and cause mastitis.

Anyone who has mastitis should receive treatment as soon as possible. If a person has symptoms of this infection for longer than 24 hours, they should speak to a doctor and ask for antibiotics.

According to the United Kingdom’s National Health Service (NHS), if a person is breastfeeding, they should avoid:

  • having breasts that are very full for very long
  • any sudden long periods between feedings
  • pressure on the breasts from fingers, bras, or other clothing

It may also help to focus on good attachment during feeding. Signs of good attachment include:

  • breastfeeding without pain
  • the darker skin around the nipple showing more above the baby’s top lip than below their bottom lip
  • the baby having a wide, open mouth
  • the chin firmly touching the breast
  • the baby having rounded, full cheeks
  • rapid sucks that turn into slow, deep sucks

According to the Office on Women’s Health, who has mastitis symptoms for longer than 24 hours should speak to a doctor and ask for antibiotics.

Anyone who thinks that they may have a breast abscess should seek medical attention.

Contact a doctor right away if there is:

  • a possible infection in both breasts
  • pus or blood in breast milk
  • red streaks on or near the affected area of the breast
  • symptoms of mastitis that come on very suddenly
  • severe symptoms of mastitis

Breast abscesses are painful, pus-filled lumps under the skin of the breast. They are a complication of a breast infection, which is called mastitis.

Mastitis tends to affect women who are breastfeeding, but anyone can develop this type of infection and a resulting abscess. People who smoke or who have obesity may have a higher risk.

Anyone who suspects that they have a breast abscess or who has had symptoms of mastitis for more than 24 hours should speak to a doctor.