Breast Infection (Mastitis)

Reviewed on 11/12/2021

What Is Breast Infection (Mastitis)?

Breast pain is a symptom of mastitis, a breast infection.
Breast pain is a symptom of mastitis, a breast infection.

Mastitis is an infection of the tissue of the breast that occurs most frequently during the time of breastfeeding. This infection causes pain, swelling, redness, and increased temperature of the breast. It can occur when bacteria, often from the infant's mouth, enter a milk duct through a crack in the nipple. This causes an infection and painful inflammation of the breast.

Breast infections most commonly occur one to three months after delivery, but may also occur in women who have not recently delivered as well as in women after menopause. Other causes of infection include chronic mastitis and a rare form of cancer called inflammatory carcinoma.

  • The breast is composed of several glands and ducts that lead to the nipple and the surrounding darkly pigmented area called the areola. The milk-carrying ducts extend from the nipple into the underlying breast tissue like the spokes of a wheel. Under the areola are lactiferous ducts. These fill with milk during lactation following delivery of an infant. When a girl reaches puberty, her body's changing hormonal makeup causes the ducts to grow and fat deposits in the breast tissue to increase. The glands that produce milk (mammary glands) that are connected to the surface of the breast by the lactiferous ducts may extend into the armpit area (axilla).
  • A breast infection that leads to an abscess (a localized pocket or collection of pus) is a more serious type of infection. If mastitis is left untreated, an abscess can develop in the breast tissue. This type of infection may require surgical drainage.

What Are Signs and Symptoms of Breast Infection?

  • Infection: Breast infections may cause pain, redness, and warmth of the breast, along with the following symptoms:
    • Tenderness and swelling
    • Body aches
    • Fatigue
    • Breast engorgement
    • Fever and chills
    • Rigor or shaking
  • Abscess: Sometimes, a breast abscess, a more serious infection, can complicate mastitis. Noncancerous masses such as abscesses are often tender and may feel mobile beneath the skin. The edge of the mass is usually regular and well defined. Indications an abscess has formed include the following:
    • A tender lump in the breast that does not get smaller after breastfeeding (If the abscess is deep in the breast, you may not be able to feel it). The mass may be moveable and/or compressible.
    • Pus draining from the nipple
    • Persistent fever and no improvement of symptoms within 48-72 hours

What Causes Breast Infection?

Mastitis (inflammation of breast tissue) is a common benign cause of a breast mass. It may be seen in women after childbirth while breastfeeding. These masses are often quite painful. Women who are not breastfeeding can also develop mastitis, although in healthy women, mastitis is rare. Women with diabetes, chronic illness, AIDS, or an impaired immune system may be more susceptible to the development of mastitis.

  • Bacteria normally found in a baby's mouth or on the nipple can enter the milk ducts through small cracks in the skin of the nipple and can multiply rapidly in the breast milk. This can lead to a superficial small area of inflammation (frequently from streptococcal bacteria) or a deeper walled-off infection or abscess (frequently from staphylococcal bacteria).
  • Mild temperature elevations (previously termed milk fever) accompanied by some breast or nipple soreness is usually secondary to engorgement and dehydration immediately (24-72 hours) after delivery, and it is treated by improved breastfeeding technique. The body temperature should not be above 39 C (102.2 F), nor should the fever persist for longer than about 4-16 hours. This condition may also occur in women who are not breastfeeding and have not yet completely suppressed lactation.
  • About one to three percent of breastfeeding mothers develop mastitis, usually within the first few weeks after delivery. Most breast infections occur within the first or second month after delivery or at the time of weaning. Typically, the infection is only in one breast. Engorgement and incomplete breast emptying can contribute to the problem and make the symptoms worse.
  • Chronic mastitis may occur in women who are not breastfeeding. In postmenopausal women, breast infections may be associated with chronic inflammation of the ducts below the nipple. Hormonal changes in the body can cause the milk ducts to become clogged with dead skin cells and debris. These clogged ducts make the breast more prone to bacterial infection. This type of infection tends to return following treatment with antibiotics.

When to Seek Medical Care for Breast Infection

Call your health care provider as soon as you feel any suspicious lump, whether you are breastfeeding or not. Call for an appointment if you experience the following:

  • You have any abnormal discharge from your nipples.
  • Breast pain is making it difficult for you to function each day.
  • You have prolonged, unexplained breast pain.
  • You have any other associated symptoms that you are worried about such as redness, swelling, pain that interferes with breastfeeding, or a mass or tender lump in the breast that does not disappear after breastfeeding.
  • If you are breastfeeding, call your doctor if you develop any symptoms of breast infection so that treatment may be started promptly.

You may need to be evaluated in a hospital's emergency department if the breast pain is associated with other signs of an infection (such as a fever, swelling, or redness to the breast), particularly if your health care provider cannot see you promptly. Go to the emergency department if you experience any of the following:

  • A persistent, high fever greater than 101.5 F (38.6 C)
  • Nausea or vomiting that is preventing you from taking antibiotics as prescribed
  • Pus draining from the breast
  • Red streaks extending toward your arm or chest
  • Dizziness, fainting, or confusion

How Do Medical Professionals Diagnose Breast Infections?

The diagnosis of mastitis or breast abscess can usually be made based on a physical examination.

  • If it is unclear whether a mass is due to a fluid-filled abscess or to a solid mass such as a tumor, an ultrasound may be done. An ultrasound may also be helpful in distinguishing between simple mastitis and abscess or in diagnosing an abscess deep in the breast. This noninvasive test allows your doctor to directly visualize the abscess by placing an ultrasound probe over your breast. If an abscess is confirmed, aspiration or surgical drainage, and IV antibiotics, are often required.
  • Cultures may be taken, either of breast milk or of material aspirated (taken out through a syringe) from an abscess, to determine the type of organism causing the infection. This information can help your doctor decide what kind of antibiotic to use.
    • The organism is usually Staphylococcus aureus.
    • Some infections may due to MRSA (methicillin-resistant Staphylococcus aureus), a form of Staphylococcus that is resistant to treatment with most antibiotics.
  • Women with mastitis when not breastfeeding, or those who do not respond to treatment, may require a mammogram or breast biopsy. This is a precautionary measure because a rare type of breast cancer can produce symptoms of mastitis.

What Is the Treatment for Breast Infection?

  • Breast infections require treatment by a health care provider.
  • For simple mastitis without an abscess, oral antibiotics are prescribed. Cephalexin (Keflex) and dicloxacillin (Dycill) are two of the most common antibiotics chosen, but a number of others are available. Erythromycin may be used if a woman is allergic to the commonly used antibiotics. The antibiotic prescribed for you will depend on the clinical situation, your doctor's preference, and your medication allergies, if any. This medicine is safe to use while breastfeeding and will not harm the baby.
  • Treatment of chronic mastitis in nonbreastfeeding women can be complicated. Recurrent episodes of mastitis are common. Occasionally, this type of infection responds poorly to antibiotics. Therefore, close follow-up with your doctor is mandatory.
  • If the infection worsens in spite of oral antibiotics or if you have a deep abscess requiring surgical drainage, you may be admitted to the hospital for IV antibiotics.

What Are Some Home Remedies for Mastitis?

After you see a doctor, try the following to help resolve your breast infection.

  • Pain medication: Take acetaminophen (such as Tylenol) or ibuprofen (such as Advil) for pain. These medicines are safe while breastfeeding and will not harm your breastfeeding baby. Your doctor may prescribe a prescription-strength pain reliever if your pain is severe and not relieved with over-the-counter medication.
  • In mild cases of mastitis, antibiotics may not be prescribed at all. If you are prescribed antibiotics, finishing the entire course of medication (even if you feel better) is very important.
  • Frequent feedings: Do not stop breastfeeding from the affected breast, even though it will be painful. Frequent emptying of the breast prevents engorgement and clogged ducts that can only make mastitis worse.
    • If needed, you can use a breast pump to completely empty the breast.
    • The infection will not harm the baby because the germs that caused the infection probably came from the baby's mouth in the first place. An alternative to this is to pump the affected breast in order to remove and discard the milk. Breastfeed from the unaffected side and supplement with infant formula as needed.
  • Pain relief: A warm compress applied before and after feedings can often provide some relief. A warm bath may work as well.
    • If heat is ineffective, ice packs applied after feedings may provide some comfort.
    • Avoid using ice packs just before breastfeeding because it can slow down milk flow.
    • Drink plenty of water—at least 10 glasses a day. Eat well-balanced meals and add 500 extra calories a day while breastfeeding. Dehydration and poor nutrition can decrease milk supply and make you feel worse.

What Is Breast Infection Surgery?

If an abscess is present, it must be drained. After injection of local anesthetic, the doctor may drain an abscess near the surface of the skin either by aspiration with a needle and syringe or by using a small incision. This can be done in the doctor’s office or emergency department.

If the abscess is deep in the breast, however, it may require surgical drainage in the operating room. This procedure is usually done under general anesthesia to minimize pain and completely drain the abscess. Antibiotics and heat on the area are also used to treat abscesses.

What Are the Next Steps for Breast Infection Treatment?

  • Mastitis does not cause cancer, but cancer can mimic mastitis in appearance.
  • If a breast infection is slow in going away, your health care provider may recommend a mammogram or other tests to rule out cancer.

What Is the Follow-up for Breast Infection?

If you have a breast infection, you will usually be seen for a recheck in 24-48 hours.

  • Take all antibiotics as prescribed.
  • Take your temperature three times a day for the first 48 hours after treatment begins.
  • Call your doctor if you develop a high fever, vomiting, increasing redness, swelling, or pain in the breast.
  • Follow up with your doctor in one to two weeks to make sure that the infection has resolved. If the infection spreads or an abscess develops, you may require IV antibiotics or surgical treatment.

Can You Prevent a Breast Infection?

Sometimes mastitis is unavoidable. Some women are more susceptible than others, especially those who are breastfeeding for the first time. In general, good habits such as the following are effective for mastitis prevention:

  • Breastfeed equally from both breasts.
  • Empty breasts completely to prevent engorgement and blocked ducts.
  • Use good breastfeeding techniques to prevent sore, cracked nipples.
  • Avoid dehydration by drinking plenty of fluids.
  • Practice careful hygiene: Handwashing, cleaning the nipples, keeping your baby clean.

What Is the Outlook for Breast Infection?

  • When treated promptly, the majority of breast infections go away quickly and without serious complications. Most women can and should continue to breastfeed despite an episode of uncomplicated mastitis. With proper treatment, symptoms should begin to resolve within one to two days.
  • A breast abscess may require surgical drainage, IV antibiotics, and a short hospital stay. A small incision is made and usually heals quite well. The prognosis for complete recovery is also good. Breastfeeding should be avoided in the infected breast when an abscess is present.
  • Postmenopausal women with breast abscesses have a high rate of recurrence after simple drainage and frequently need to follow up with a surgeon for more definitive treatment.
  • Chronic infection can result if an abscess is not completely drained, and this can result in a poor cosmetic result.

Breast Infection Support Groups and Counseling

  • La Leche League, a network of international and local groups, is dedicated to helping mothers breastfeed

Health Solutions From Our Sponsors

Reviewed on 11/12/2021
Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.