Mastitis, which mainly affects breast-feeding women, causes redness, swelling and pain in one or both breasts.
Mastitis is an inflammation of breast tissue that sometimes involves an infection. The inflammation results in breast pain, swelling, warmth and redness. You might also have fever and chills.
Mastitis most commonly affects women who are breast-feeding (lactation mastitis). But mastitis can occur in women who aren't breast-feeding and in men.
Lactation mastitis can cause you to feel run down, making it difficult to care for your baby. Sometimes mastitis leads a mother to wean her baby before she intends to. But continuing to breast-feed, even while taking an antibiotic to treat mastitis, is better for you and your baby.
Products & Services
Signs and symptoms of mastitis can appear suddenly. They may include:
- Breast tenderness or warmth to the touch
- Breast swelling
- Thickening of breast tissue, or a breast lump
- Pain or a burning sensation continuously or while breast-feeding
- Skin redness, often in a wedge-shaped pattern
- Generally feeling ill
- Fever of 101 F (38.3 C) or greater
When to see a doctor
See your doctor if you have breast symptoms that concern you.
From Mayo Clinic to your inbox
Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on managing health.
ErrorEmail field is required
ErrorInclude a valid email address
To provide you with the most relevant and helpful information, and understand which
information is beneficial, we may combine your email and website usage information with
other information we have about you. If you are a Mayo Clinic patient, this could
include protected health information. If we combine this information with your protected
health information, we will treat all of that information as protected health
information and will only use or disclose that information as set forth in our notice of
privacy practices. You may opt-out of email communications at any time by clicking on
the unsubscribe link in the e-mail.
Thank you for subscribing!
You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox.
Sorry something went wrong with your subscription
Please, try again in a couple of minutes
Milk that is trapped in the breast is the main cause of mastitis. Other causes include:
- A blocked milk duct. If a breast doesn't completely empty at feedings, one of your milk ducts can become clogged. The blockage causes milk to back up, leading to breast infection.
- Bacteria entering your breast. Bacteria from your skin's surface and baby's mouth can enter the milk ducts through a crack in the skin of your nipple or through a milk duct opening. Stagnant milk in a breast that isn't emptied provides a breeding ground for the bacteria.
Female breast anatomy
The structure of the female breast is complex — including fat, glandular and connective tissue, as well as lobes, lobules, ducts, lymph nodes, blood vessels and ligaments.
Lobules and ducts
Each breast has a number of sections (lobules) that branch out from the nipple. Each lobule holds tiny, hollow sacs (alveoli). The lobules are linked by a network of thin tubes (ducts). If you're breast-feeding, ducts carry milk from the alveoli toward the dark area of skin in the center of the breast (areola). From the areola, the ducts join together into larger ducts ending at the nipple.
Fat, ligaments and connective tissue
Spaces around the lobules and ducts are filled with fat, ligaments and connective tissue. The amount of fat in your breasts largely determines their size. The actual milk-producing structures are nearly the same in all women. Female breast tissue is sensitive to cyclic changes in hormone levels. Most women's breast tissue changes as they age, with more fat relative to the amount of dense tissue.
The breast has no muscle tissue. Muscles lie underneath the breasts, however, separating them from your ribs.
Arteries and capillaries
Oxygen and nutrients travel to breast tissue through the blood in your arteries and capillaries — thin, fragile blood vessels.
Lymph nodes and lymph ducts
The lymphatic system is a network of lymph nodes and lymph ducts that helps fight infection. Lymph nodes — found under the armpit, above the collarbone, behind the breastbone and in other parts of the body — trap harmful substances that might be in the lymphatic system and safely drain them from the body.
Risk factors for mastitis include:
- Previous bout of mastitis while breast-feeding
- Sore or cracked nipples — although mastitis can develop without broken skin
- Wearing a tightfitting bra or putting pressure on your breast when using a seat belt or carrying a heavy bag, which may restrict milk flow
- Improper nursing technique
- Becoming overly tired or stressed
- Poor nutrition
Mastitis that isn't adequately treated or that is due to a blocked duct can cause a collection of pus (abscess) to develop in your breast. An abscess usually requires surgical drainage.
To avoid this complication, talk to your doctor as soon as you develop signs or symptoms of mastitis.
To get your breast-feeding relationship with your infant off to its best start — and to avoid complications such as mastitis — consider meeting with a lactation consultant. A lactation consultant can give you tips and provide invaluable advice for proper breast-feeding techniques.
Minimize your chances of getting mastitis by following these tips:
- Fully drain the milk from your breasts while breast-feeding.
- Allow your baby to completely empty one breast before switching to the other breast during feeding.
- Change the position you use to breast-feed from one feeding to the next.
- Make sure your baby latches on properly during feedings.
- If you smoke, ask your doctor about smoking cessation.
Sept. 13, 2022
- AskMayoExpert. Mastitis. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2017.
- Ferri FF. Mastitis. In: Ferri's Clinical Advisor 2018. Philadelphia, Pa.: Elsevier; 2018. https://www.clinicalkey.com. Accessed May 17, 2018.
- Dixon JM. Nonlactational mastitis in adults. https://www.uptodate.com/contents/search. Accessed May 17, 2018.
- Lobo RA, et al. Breast diseases: Detection, management, and surveillance of breast disease. In: Comprehensive Gynecology. 7th ed. Philadelphia, Pa.: Elsevier; 2017. https://www.clinicalkey.com. Accessed May 17, 2018.
- Mastitis. La Leche League International. https://www.llli.org/breastfeeding-info/mastitis/. Accessed May 17, 2018.
- Dixon JM. Lactational mastitis. https://www.uptodate.com/contents/search. Accessed May 17, 2018.
- Gabbe SG, et al., eds. Lactation and breastfeeding. In: Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, Pa.: Elsevier; 2017. https://www.clinicalkey.com. Accessed May 17, 2018.
Products & Services