Your gift is 100% tax deductible.
Mastitis
Mastitis is swelling or inflammation in the breast. It is often caused by an infection. It is most common when a woman is breastfeeding, but it can happen at other times as well.
A clogged milk duct that doesn't let milk fully drain from the breast or breaks in the skin of the nipple can lead to infection. This causes the body’s white blood cells to release substances to fight the infection, which can lead to swelling and increased blood flow.
Symptoms and diagnosis of mastitis
Mastitis can often be diagnosed based on symptoms and the results of a breast exam. It usually affects only one breast.
The affected part of the breast may become swollen, painful, and warm to the touch. You may also notice a change in skin color. In some cases, a breast abscess may form. This is a collection of pus, which might feel like a lump. If you have mastitis that’s caused by an infection, symptoms can include fever, headache, and general flu-like symptoms.?
How does mastitis affect your risk of breast cancer?
Having mastitis does not raise your risk of developing breast cancer.
Does mastitis need to be treated?
Mastitis related to breastfeeding can often be managed by continuing to breastfeed regularly. You can reduce swelling by applying warm or cold compresses and taking pain relievers such as acetaminophen or ibuprofen.
If infection is suspected, mastitis is treated with antibiotics. If you’re breastfeeding, you’ll likely be encouraged to empty the milk from your breast regularly. Abscesses are treated by draining the pus. This is done either by surgery or by aspiration using a thin, hollow needle, often guided by ultrasound. Antibiotics are often prescribed as well.
Inflammatory breast cancer has symptoms that can appear similar to mastitis and can be mistaken for an infection. If you’ve been diagnosed with mastitis and antibiotic treatment doesn’t help within about a week, you might need a skin biopsy to be sure it’s not cancer. Inflammatory breast cancer can spread quickly. It is important that you see your health care team if you still have symptoms after antibiotic treatment.
- Written by
- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
Collins LC, Schnitt SJ. Chapter 9: Pathology of benign breast disorders. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2014.
Dixon JM. Lactational mastitis. UpToDate. 2026. Accessed at https://www.uptodate.com/contents/lactational-mastitis on March 13, 2026.
Dixon JM, Bundred NJ. Chapter 5: Management of disorders of the ductal system and infections. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2014.
Orr B, Kelley JL. Benign breast diseases: Evaluation and management. Clin Obstet Gynecol. 2016;59(4):710-726.
Last Revised: May 26, 2026
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
American Cancer Society Emails
Sign up to stay up-to-date with news, valuable information, and ways to get involved with the American Cancer Society.