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What is mastitis?

Mastitis is a condition that causes a woman's breast tissue to become painful and inflamed.

Mastitis is most common in breastfeeding women, although women who aren't breastfeeding can develop it.

About 1 in 10 breastfeeding women are affected by mastitis. In these cases, it usually develops in the first three months after giving birth.

Doctors often refer to it as lactation mastitis or puerperal mastitis.

Mastitis usually affects one breast. As well as the breast being painful and swollen, some women may also experience flu-like symptoms such as a high temperature (fever), aches and chills.

Read more about the

symptoms of mastitis

You should visit your doctor immediately if you think you might have mastitis. They should be able to diagnose it.

If you're breastfeeding, they may ask you to demonstrate your technique. Try not to feel as if you are being tested or blamed, breastfeeding correctly can take time and practice.

In non-breastfeeding women, your doctor will want to rule out other conditions, see

breast lumps
for more information.

Read more about

how mastitis is diagnosed

What causes mastitis?

Mastitis can be caused by an infection or milk remaining in the milk tissue (milk stasis).

Milk stasis can occur for a number of reasons, such as your baby not being properly attached to your breast during feeding.

Infectious mastitis may develop if bacteria gets into your milk ducts. This can be because your milk ducts are blocked or, in non-breastfeeding women, because of a cracked or sore nipple, or nipple piercing.

Left untreated, non-infectious mastitis can develop into infectious mastitis. This may be due to bacteria infecting milk that remains in the breast tissue.

Read more about the

causes of mastitis

Treating mastitis

Most cases of mastitis can be effectively treated.

Rest, drinking plenty of fluids and, if necessary, adjusting your breastfeeding technique, may be all that is needed.

When breastfeeding, make sure your baby is properly attached to your breast and that your nipple is positioned deep inside your baby's mouth.

Your breast should feel softer and lighter after the feed but there may still be a small amount of milk left over. In some cases it may be necessary to:

  • feed more frequently
  • express any remaining milk after a feed
  • express milk between feeds

Read more about expressing and storing breast milk.

All cases of infectious mastitis will need to be treated with

to bring the infection under control.

Read more about

treating mastitis

Can I still breastfeed with mastitis?

Although the symptoms of mastitis may discourage you from breastfeeding, it is important that you try to continue. Regular breastfeeding will help:

  • remove any blocked breast milk from your breast
  • resolve symptoms of mastitis more quickly
  • prevent mastitis from becoming more serious

The milk from the affected breast may be a little saltier than normal, but it is safe for your baby to drink. Any bacteria present in the milk will be harmlessly absorbed by the baby's digestive system and will not cause any problems

If you have severe or persistent mastitis, your doctor may decide to take a small sample of your breast milk for testing.

Complications of mastitis

Mastitis should be promptly treated to prevent more serious complications developing , such as a

breast abscess
(a painful collection of pus).

Read more about the

complications of mastitis

Mastitis symptoms

Mastitis usually only affects one breast and symptoms often develop quickly.

These symptoms include:

  • a red, swollen area on your breast that may feel hot and painful to touch
  • an area of hardness on your breast
  • a burning pain in your breast that may be continuous or may only occur when you are breastfeeding
  • nipple discharge
    - which may be white or may contain streaks of blood

Over half of women with mastitis may also experience flu-like symptoms such as:

  • aches
  • high temperature (fever) of 38C (100.4F) or above
  • shivering and chills
  • tiredness
  • feeling generally unwell

Visit your doctor immediately if you experience these symptoms, and you also have a red, tender area on your breast.

Mastitis is not usually a serious condition, but advice and prompt treatment may be needed to stop the condition getting worse.

Speaking to your doctor or midwife will also help to reassure you.

Mastitis causes

Mastitis can have different causes depending on whether it is infectious or not.

Non-infectious mastitis

Most cases of non-infectious mastitis are thought to be caused by milk stasis. Milk stasis occurs when the milk is not properly removed from your breast during breastfeeding. It can be caused by:

  • your baby not being properly attached to your breast during feeding - which may mean that not enough milk is removed or it may cause pain in your nipple
  • your baby having problems sucking - for example, because they have a
    (a piece of skin between the underside of their tongue and the floor of their mouth)
  • your baby having infrequent feeds or missing feeds - for example, when they start to sleep through the night
  • your baby favouring one breast for breastfeeding - this can lead to milk stasis developing in the other breast
  • pressure on your breast - for example, from tight-fitting clothing, an over-restrictive bra or sleeping on your front

Milk stasis can cause the milk ducts in your breasts to become blocked.

Experts are not sure why breast milk can cause the breast tissue to become inflamed. However, one theory is that it may be due to the presence of special proteins called cytokines in your breast milk.


Cytokines are proteins used by the immune system. They are passed on to your baby to help them resist infection.

It may be that your immune system mistakes cytokines for a bacterial or viral infection and responds by inflaming the breast tissue in an effort to stop the spread of infection.

Infectious mastitis

Fresh human milk does not usually provide a good environment in which bacteria can breed. However, if your milk ducts become blocked, milk can stagnate and an infection can develop.

Exactly how bacteria enter the breast tissue has not been conclusively proven. It may be that:

  • bacteria that usually live harmlessly on the skin of your breast enter through a small crack or break in your skin
  • bacteria present in the baby's mouth and throat are transferred during breastfeeding

You may be at greater risk of developing infectious mastitis if:

  • your nipple is damaged - for example, as a result of using a manual breast pump incorrectly; a breast pump is a device that is used to express milk from your breast
  • your baby has a
    cleft lip or palate
    (an opening or split in their lip or roof of their mouth); this can also damage your nipple

Mastitis in non-breastfeeding women

In women who don't breastfeed, mastitis is caused by an infection.

This can be due to bacteria getting into the milk ducts through a cracked or sore nipple, or a nipple piercing.

There are two different types of mastitis that affect women who are not breastfeeding. These are:

  • periductal mastitis - which usually affects women who are in their late 20s and early 30s, and is more common among smokers
  • duct ectasia - which tends to affect women in the years before the
    (when a woman’s periods stop), or after the menopause

Mastitis diagnosis

Your doctor should be able diagnose mastitis after examining your breast and asking about your symptoms.

As mastitis is usually the result of problems with breastfeeding, your doctor or midwife may ask you to demonstrate your breastfeeding technique.

You should not feel as if you are being tested or blamed. Breastfeeding can take time and practice to get right and sometimes you may need advice.

If you're not breastfeeding, your doctor will want to rule out other conditions as a

breast lump
can be a sign of breast cancer.

Breast milk sample

Your doctor may decide to take a small sample of your breast milk for testing. This may be necessary if:

  • you have severe mastitis
  • you have had repeated episodes of mastitis
  • antibiotics
    have been used to treat an infection but they have not improved your condition

Your breast milk can be tested for a bacterial infection and to identify the bacteria responsible. This will help to determine your treatment.

Mastitis treatment

Mastitis can usually be easily treated and most women will make a full recovery very quickly.

Non-infectious mastitis

Most cases of non-infectious mastitis can be treated using a number of self care techniques such as:

  • making sure you get plenty of rest
  • drinking plenty of fluids
  • using over-the-counter painkillers, such as
    , to reduce pain and fever; a small amount of paracetamol can enter the breast milk but it is not enough to harm your baby (aspirin is not safe to take while breastfeeding)
  • not wearing tight-fitting clothing or a bra until your symptoms improve
  • placing a warm compress (a cloth soaked with warm water) over your breast to help relieve the pain; a warm shower or bath may also help

Breastfeeding advice

You should try to continue breastfeeding if you have mastitis. Following the advice outlined below should improve your symptoms.

  • Keep breastfeeding or expressing milk by hand or using a pump (a device to help you express milk). If necessary, express milk between feeds.
  • Feed from the affected breast regularly (at least 8-12 times a day) if you are only breastfeeding your baby (that is, if you are not bottle feeding as well).
  • Make sure that your breast is empty after feeds by expressing any remaining milk.
  • Massage your breast to release any blockages. Stroke from the lumpy area towards your nipple to help the milk flow.
  • Make sure that your baby is properly positioned and attached to your breasts. Your midwife or health visitor will advise you about how to do this.
  • Experiment by feeding your baby in different positions to see whether it makes feeding more effective.
  • Warming your breast with warm water can soften it, making it easier for your baby to feed.

Visit your doctor for additional advice or treatment if your symptoms do not improve or they get worse despite trying these techniques.

Infectious mastitis

Infectious mastitis will need to be treated using a combination of the above techniques and

(medication to treat infections caused by bacteria).

If you are breastfeeding, your doctor will prescribe an antibiotic that is safe to use. This will usually be a tablet or capsule that you take orally (by mouth) four times a day.

A very small amount of the antibiotic may enter your breast milk and may make your baby irritable and restless or your baby’s stools looser (runnier) and more frequent.

These effects are usually temporary and will resolve once you have finished the course of antibiotics. They do not pose a risk to your baby.

Sore nipples

Your nipples may become sore if your baby is not properly attached during feeding. Your doctor, midwife or health visitor will be able to advise about [how to improve your breastfeeding technique].

If your nipples do not heal, you should return to your doctor because you may have an infection. If you still have mastitis or pain in your breast, your doctor may prescribe an oral antibiotic (see above).

Sore nipples can also be a sign of

, a fungal infection caused by the yeast fungus, Candida albicans. If you have thrush, you may also have:

  • a burning pain in your breast
  • very itchy breasts
  • pain that is worse at night or after feeding

Your doctor may prescribe a cream that you will need to apply to your breasts after every feed, for two weeks. Your baby may also need to be treated if they develop thrush in their mouth.

Read more about

oral thrush in babies

Mastitis complications

In severe cases of infectious mastitis, an abscess can develop in the breast.

A breast abscess is a painful collection of pus that forms in the breast, just under the skin.

As well as causing a painful lump to develop, a breast abscess may also:

  • be red
  • feel hot
  • cause the skin over it to swell
  • cause a high temperature (fever) of 38C (100.4F) or above

The abscess can be treated using a needle or a small incision to drain the pus out of your breast.

Read more about

breast abscesses

One study found that 3 out of 100 women who were treated for mastitis with

(medication to treat infections caused by bacteria) developed an abscess. Some different research estimated that 1 in 10 women who develop an abscess may be unable to breastfeed again.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.