Mastitis causes inflammation of the breast tissue that sometimes occurs with breast infection. It is non-contagious.

Mastitis is a fairly common condition; as many as 1 in 10 breastfeeding people in the U.S. will get lactation mastitis (also known as puerperal mastitis), typically 1-3 months after their baby is born.

Due to the inflammation, someone with mastitis may experience breast pain, engorgement, redness, and may sometimes experience fever or chills.

What causes mastitis?

During breastfeeding, hormones are released to create milk flow.

Prolactin causes your alveoli (part of the lungs) to take protein and sugar from the blood and turn them into breast milk. Then, oxytocin is released, causing the cells around the alveoli to contract and force the breast milk towards the milk ducts in the mammary gland.

When milk supply gets trapped in the milk ducts and cannot be released, mastitis occurs.

Other causes of mastitis

A bacterial infection. During breastfeeding, bacteria from your skin and baby’s mouth can enter the duct through the opening or cracked nipple skin. Stagnant milk in the affected breast (“milk stasis”) becomes a breeding ground for bacteria.

Bacterial infections can also occur in those who are not breastfeeding, specifically after menopause. The ducts below the nipple can become inflamed or clogged with dead skin cells and debris due to hormonal changes. For those not breastfeeding, this is known as chronic/acute mastitis or periductal mastitis.

A clogged milk duct. Sometimes the breast doesn’t completely empty after breastfeeding, causing a build up of breast milk. The clogged duct causes milk to back up, leading to a breast infection.

Nipple damage. If the nipple is cracked or damaged, it makes it easier for harmful bacteria to enter the breast and cause infectious mastitis.

Yeast infection. Secondary infections such as thrush (yeast infection) can cause inflammation and a blocked milk duct and mastitis.

Symptoms and risk factors for mastitis


Mastitis symptoms often appear suddenly, and may include:

  • A sore breast (mastalgia) or sore nipples.
  • A red, painful, or hot “wedge-shaped” swelling on the affected breast, or both breasts.
  • A red, painful or hot lump in your breast.
  • Hot, swollen breasts (engorgement).
  • Painful or burning sensation while breastfeeding.
  • Red streaks on your breasts.
  • Body aches, back pain and headaches.
  • Chills.
  • Fever of 100.4°F (38°C) or higher, or as directed by your healthcare provider.
  • General ill feeling or flu like symptoms, including sore throat.

If you have these symptoms, consult your healthcare provider as soon as possible.

Seek immediate medical care if you have these symptoms:

  • A persistent, high fever over 101.5°F.
  • Dizziness, confusion or fainting.
  • Nausea or vomiting preventing you from taking antibiotics, if prescribed.
  • Pus or blood draining from the breast.
  • Red streaks extending from the breast towards the chest or arms.

Those at risk of getting mastitis

Risk factors include:

  • Being overly stressed or exhausted.
  • Diabetes or autoimmune diseases.
  • Eating poorly or having insufficient nutrition.
  • Having breast implants or nipple piercings.
  • Having sore or cracked nipples.
  • Having had mastitis while breastfeeding in the past.
  • Practicing improper nursing techniques.
  • Skin conditions such as eczema.
  • Smoking.
  • Wearing a tight bra or anything that puts pressure on the breast, which may restrict the flow of milk.

Diagnosing mastitis

To diagnose mastitis, your healthcare provider will conduct a physical exam and ask you about your symptoms. They will examine the infected breast. In most cases, you won’t need lab tests. But you may need the following tests:

  • Milk sample (breast milk culture). The doctor will take a sample of your breast milk to determine the best antibiotic for treatment. This may be done if an infection is severe, occurred in the hospital or hasn’t responded to a previous course of antibiotics.
  • Ultrasound. This noninvasive imaging test allows your doctor to visualize what is blocked inside your breast and if you have an abscess. You may need this imaging test if the mastitis is linked to breastfeeding and doesn’t get better with treatment in 48 to 72 hours.
  • Blood cultures. These will be done if the breast redness keeps growing or your vital signs become unstable.

Treating mastitis


Sometimes mastitis symptoms can go away on their own. If not, mastitis treatment typically involves an antibiotic prescription followed by painkillers to alleviate the symptoms.

Antibiotics for breast infection. If you have a breast infection, your doctor will typically recommend a 10-day course of antibiotic treatment of dicloxacillin, or alternatives such as erythromycin or clindamycin if you have a penicillin allergy.

For proper treatment, make sure to finish all of your antibiotic medication to reduce the chance of getting recurrent mastitis (when mastitis comes back).

If your symptoms do not clear up and your affected breast is still inflamed after your course of antibiotics, follow up with your doctor on how to proceed.

Sometimes nonsteroidal anti-inflammatory drugs (NSAIDS) or pain relievers are also recommended to ease symptoms. Tylenol, Advil, Motrin or other over-the-counter pain relievers will help you manage the inflammation and irritation.

Continue breastfeeding

Lactational mastitis can be a tiring experience and make it difficult to care for a new baby, but it is important to continue breastfeeding – even while taking antibiotics for mastitis – to maintain your health and the health of your baby. In some cases, breastfeeding can help the infection clear up, relieve engorgement and allow normal lactation to resume.

At home, amidst a course of antibiotics and painkillers, the following practices are recommended to help relieve discomfort for lactational mastitis, including:

  • Avoid letting breast milk overfill your breast before feeding.
  • Apply cold compresses to your breasts after breastfeeding (not before, as the coldness may slow milk production).
  • Remove any dried milk secretions with warm water.
  • Rest as much as possible.
  • Wear a supportive bra that doesn’t constrict or put too much pressure on your breasts.

With proper treatment, mastitis often begins to go away after a few days.

Frequently asked questions (FAQs) about mastitis

Are there ways to prevent mastitis?

For those who are breastfeeding, it is recommended to meet with a lactation consultant to prevent mastitis or other complications. They will teach you the correct ways to breastfeed and offer tips to make the process go more smoothly.

Some general prevention tips for breastfeeding individuals include:

  • Changing the position you use to breastfeed for each feeding.
  • Ensuring your baby latches properly during feedings.
  • Fully draining the milk from your breasts after a breastfeeding session, encouraging your baby to completely empty one breast before alternating to the other.
  • Massaging the breast during feeding or pumping from the top towards the nipple.
  • Practicing careful hygiene, especially handwashing, cleaning the nipples and ensuring your baby is clean before feeding.

For those not breastfeeding, preventative measures include:

  • Drinking plenty of fluids.
  • Practicing careful hygiene, especially hand washing and cleaning the nipples.
  • Preventing moisture from accumulating on the breast and nipples.
  • Quitting smoking or speaking to your doctor about smoking cessation methods.
Can having mastitis lead to other complications?

In some instances, mastitis can become severe enough that an abscess forms (when the hollow area in breast tissue fills with pus). An abscess is often painful and requires medical attention, but is not deadly unless it goes untreated and spreads to other bodily tissues.

  • For those with mastitis that also have a breast abscess, surgical drainage, IV antibiotics or a hospital stay may be needed to monitor your healing and prevent the abscess from getting worse.

Very rarely, mastitis can lead to sepsis which requires urgent hospitalization and IV antibiotics. Signs of sepsis from mastitis include vomiting, diarrhea, slurred speech or extreme confusion.

To avoid an abscess or sepsis, talk to your doctor as soon as you develop signs or symptoms of mastitis to get the appropriate treatment early on and to prevent any complications.

Can other conditions be mistaken for mastitis?

Sometimes a milk blister can be mistaken as mastitis. Also known as a bleb, a milk blister is a painful white dot on the nipple or areola caused by blocked milk flow towards the opening of the nipple or skin overgrowth at the opening of the duct. Milk blisters can be resolved over a few weeks without any treatment.

Your doctor may also evaluate if you have symptoms that indicate a different disease such as inflammatory breast cancer. This rare form of breast cancer causes redness and swelling that can be mistaken for mastitis. To get an accurate diagnosis, your doctor may recommend a mammogram and/or ultrasound, as well as a course of antibiotics. If symptoms persist after treatment, you may additionally need a biopsy to make sure you don’t have breast cancer.


American Cancer Society. Mastitis (

National Center for Biotechnology Information (NCBI): National Library of Medicine. Acute Mastitis (

American Academy of Family Physicians. Management of Mastitis in Breastfeeding Women (