Was this helpful?

What is mastitis?

Mastitis is an infection and inflammation of the breast, usually the fatty tissue of the breast, that causes redness, pain and swelling. As this swelling pushes on the milk ducts, it causes pain.

Mastitis is usually caused by an infection with the bacteria Staphylococcus aureus. These bacteria are normally present on your skin, but cause problems when they enter the body. Bacteria causing mastitis enter through a break or crack in the skin of the breast, usually on the nipple. In fact, mastitis usually occurs in women who are breastfeeding because the nipples often become dry and irritated and can become cracked during nursing. This allows the bacteria to invade breast tissue, in particular the milk ducts and milk glands.

Mastitis in a nonbreastfeeding woman is more common after menopause than before. In very rare cases, this may indicate the presence of another primary disease, such as breast cancer. At the same time, a clogged milk duct can mimic mastitis. While a woman adjusts to breastfeeding a new infant, the milk ducts inside the breast can become clogged, causing tenderness, redness, lumps and even heat under the skin surface, but without infection.

It is possible in many cases to determine yourself if you have a clogged milk duct as opposed to mastitis. You can usually relieve a clogged milk duct by massaging the area. If these symptoms persist, however, or if you develop fever and muscle pains or body aches, it is more likely that you have indeed developed mastitis. Fortunately, mastitis can be easily treated.

While mastitis is almost never an emergency, left untreated it can lead to a breast abscess, which is a collection of pus in a hollow area in the breast. Your doctor may need to drain the abscess. A wiser course is to never let mastitis lead to an abscess.

Seek prompt medical care if you find you have trouble relieving breast engorgement even while nursing, if you develop heat, tenderness, lumping or swelling in the breast—whether breastfeeding or not—or if you develop flu-like symptoms. Seek prompt medical care if you are breastfeeding and the symptoms do not resolve by massaging the area to unclog a milk duct.

What are the symptoms of mastitis?

Infection of the breast by the bacteria Staphylococcus aureus causes symptoms, which can mimic a clogged milk duct or an abscess. Unlike a clogged duct, mastitis does not go away on its own or by massaging the affected area. Women with mastitis feel remarkably ill.

Common symptoms of mastitis

You may experience these symptoms whether you are breastfeeding or not. In mastitis, the symptoms do not usually resolve without intervention either in breastfeeding technique or by taking antibiotics. The most common symptoms include:

Symptoms that might indicate a serious condition

In some cases, mastitis can indicate a more serious condition that should be immediately evaluated. A breast abscess can be a complication of mastitis, and if left untreated, can lead to gangrene and permanent damage. If the infection spreads into the bloodstream, it can lead to sepsis (life-threatening bacterial blood infection) and organ failure. Seek immediate medical care (call 911) if you, or someone you are with, have painful, inflamed breasts and have developed any of these more serious symptoms of sepsis including:

  • Confusion or loss of consciousness for even a brief moment
  • Difficulty breathing or rapid breathing
  • Fainting or change in level of consciousness or lethargy
  • High fever (higher than 101 degrees Fahrenheit)

What causes mastitis?

Mastitis is usually caused by an infection with the bacteria Staphylococcus aureus. You normally have these bacteria on your skin but it can cause infections if it enters the body through a break or crack in the skin; in mastitis, such a break or crack is usually on the nipple. Therefore it is common in women who are breastfeeding, when the nipples become tender and dry and can crack easily. However, nonbreastfeeding women can get mastitis, too.

Other causes can include an oversupply of breast milk or another, primary bacterial infection of the breast. No genetic tendency has been found for mastitis, and while infectious, it is not contagious.

What are the risk factors for mastitis?

There is no genetic risk for developing mastitis. Not all people with risk factors will develop mastitis. Risk factors for mastitis include:

  • Abrupt weaning of a breastfeeding infant (which can lead to engorgement)
  • Breastfeeding too infrequently, contributing to blocked milk ducts
  • Breastfeeding without taking proper hygiene precautions
  • Cracked, dry nipples
  • First-time breastfeeding mothers
  • Separate, primary breast infection

Reducing your risk of mastitis

You may be able to lower your risk of mastitis by:

  • Washing your hands frequently and practicing good hygiene
  • Carefully treating cracked, dry or sensitive nipples
  • Using moisturizers to prevent cracked nipples
  • Carefully treating any other infection of the breast

If you are breastfeeding, you may be able to lower your risk of mastitis by:

  • Cleaning your nipple before and after breastfeeding
  • Massaging breast lumps during breastfeeding
  • Massaging blocked breast ducts
  • Weaning an infant gradually rather than abruptly to prevent engorgement

How is mastitis treated?

The first choice for treating mastitis is to practice prevention. However, mastitis is usually curable with timely treatment with antibiotics and, in some cases, fever-reducing agents.

If you are breastfeeding, you will most likely be encouraged to continue breastfeeding, since this often actually helps relieve pressure; the infection will not enter the breast milk. Nursing with the unaffected breast first helps facilitate letdown. Keep in mind that if you are breastfeeding, you should take pain relievers only on the advice of your doctor.

Most common medications for treating mastitis

Antibiotics are effective in treating mastitis. Specifically, beta-lactamase stable penicillins like dicloxacillin (Dycill) or cephalexin (Keflex) are safe to use while breastfeeding. There has been a significant rise in the number of community-based (outside of the hospital) antibiotic resistant infections. Laboratory culture testing will help determine the best antibiotic options. In cases in which the infection is due to a form of Staphylococcus aureus bacteria that is resistant to conventionally used drugs (methicillin-resistant Staphylococcus aureus, or MRSA), other antibiotics may be required, including intravenous antibiotics.

What you can do to improve your mastitis

You can take steps to improve the symptoms of mastitis while following your treatment plan. These include:

  • Applying warm washcloths to the affected area
  • Getting plenty of rest
  • Increase the frequency of breastfeeding
  • Keeping the nipple area moisturized
  • Massaging the breasts with warm castor oil

What are the potential complications of mastitis?

Mastitis can sometimes lead to an abscess (a hollow area in the breast tissue that becomes filled with pus). An abscess is painful and demands attention but is generally not life threatening unless it is left untreated and spreads to other tissues of the body. If this happens, sepsis (life-threatening bacterial blood infection) and organ failure can develop, both of which can be life threatening. With prompt medical care, you can help minimize your risk of serious complications by following the treatment plan you and your health care professional design specifically for you. Complications of mastitis include:

  • Breast abscess
  • Organ failure
  • Sepsis
Was this helpful?
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 18
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Breast infection. PubMed Health, a service of the NLM from the NIH.
  2. Overcoming breastfeeding problems. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
  3. Srivastava A, Mansel RE, Arvind N, et al. Evidence-based management of Mastalgia: a meta-analysis of randomised trials. Breast 2007; 16:503.
  4. Tierney LM Jr., Saint S, Whooley MA (Eds.) Current Essentials of Medicine (4th ed.). New York: McGraw-Hill, 2011.