Breast infection (mastitis)

Mastitis is a condition that causes a woman's breast tissue to become painful and inflamed. It can usually be treated easily, but it's important to see your GP if you think you have it.

Mastitis is most common in breastfeeding women. Up to 1 in every 10 women who breastfeed are affected, usually within the first three months after giving birth.

Mastitis related to breastfeeding is sometimes called lactation mastitis or puerperal mastitis by doctors.

However, women who aren't breastfeeding can also develop mastitis. Non-breastfeeding women often have a type called periductal mastitis.

What causes mastitis?

In breastfeeding women, mastitis is often caused by a build-up of milk within the breast. This is known as milk stasis.

Milk stasis can occur for a number of reasons, including:

a baby not properly attaching to the breast during feeding
a baby having problems sucking
infrequent feeds or missing feeds

In some cases, this build-up of milk can also become infected with bacteria. This is known as infective mastitis.

In non-breastfeeding women, mastitis most often occurs when the breast becomes infected as a result of damage to the nipple, such as a cracked or sore nipple, or a nipple piercing.

Symptoms of mastitis

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

Symptoms of mastitis can include:

a red, swollen area on your breast that may feel hot and painful to touch
a breast lump or 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 contain streaks of blood

You may also experience flu-like symptoms, such as aches, a high temperature (fever), chills and tiredness.

When to seek medical advice

You should contact your GP as soon as possible if you think you might have mastitis. Before your appointment it may help to try some self-help measures (see below).

It's important to see your GP promptly because there is a risk that mastitis could lead to a breast abscess (a painful collection of pus), which may need to be drained surgically.

Breast abscesses can be serious if not spotted or treated quickly; it's estimated that 1 in every 10 women who develop them are unable to breastfeed using the affected breast again.

Diagnosing mastitis

Your GP will often be able to diagnose mastitis based on your symptoms and an examination of your breasts.

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.

If your symptoms are particularly severe, you have had recurrent episodes of mastitis, or you have been given antibiotics and your condition hasn't improved, your GP may decide to take a small sample of your breast milk for testing.

This will help determine whether you have a bacterial infection and can identify the specific type of bacteria responsible for your condition. Knowing which bacteria are causing the infection will allow your GP to prescribe an antibiotic that is specifically effective against those bacteria.

If you have mastitis and are not breastfeeding, your GP may refer you to hospital for a specialist examination and a breast scan to rule out other conditions, particularly if your symptoms haven’t improved after a few days of treatment. Scans you may have include an ultrasound scan or a mammogram (X-ray of the breast).

How mastitis is treated

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

Self-help measures are often helpful, such as:

getting plenty of rest and staying well hydrated
using over-the-counter painkillers, such as paracetamol or ibuprofen, to reduce any pain or fever
avoiding tight-fitting clothing (including bras) until your symptoms improve
if you are breastfeeding, continuing to feed your baby and making sure your baby is properly attached to your breast

Breastfeeding your baby when you have mastitis, even if you have an infection, will not harm your baby and can help improve your symptoms. It may also help to feed more frequently than usual, express any remaining milk after a feed and express milk between feeds.

For non-breastfeeding women with mastitis, and breastfeeding women with a suspected infection, a course of antibiotic tablets will usually be prescribed to bring the infection under control.

Preventing mastitis

Although mastitis can usually be treated easily, the condition can recur if the underlying cause is not addressed.

If you are breastfeeding, you can help reduce your risk of developing mastitis by taking steps to stop milk building up in your breasts, such as:

breastfeed exclusively for around six months, if possible
encourage your baby to feed frequently, particularly when your breasts feel overfull
ensure your baby is well attached to your breast during feeds – ask for advice if you are unsure (see below)
let your baby finish their feeds – most babies will release the breast when they have finished feeding; try not to take your baby off the breast unless they are finished
avoid suddenly going longer between feeds – if possible, cut down gradually
avoid pressure on your breasts from tight clothing, including bras

Your GP, midwife or health visitor can advise about how to improve your breastfeeding technique. You can also call the National Breastfeeding Helpline on 0300 100 0212 for advice.