Mastitis (Breast Infection)

Mastitis (inflammation or infection of the breast) is common in breast-feeding women. It is treated with a course of antibiotics. It is best to try to continue to breast-feed if you have mastitis. Breast-feeding when you have mastitis will not harm your baby.

Cross-section diagram of a breast

Mastitis is an inflammation of the breast, usually caused by an infection.

Mastitis most commonly occurs in mothers who are breast-feeding. It typically occurs within the first few weeks of breast-feeding. As many as 1 in 3 breast-feeding mothers may have mastitis. Sometimes it occurs if you suddenly stop breast-feeding and the breasts become very swollen and sore because of the milk.<\p>

Mastitis sometimes occurs in women who are not breast-feeding. Bacteria get into the milk ducts of the breast to cause the infection. This may be through a crack or sore in the nipple or from a nipple piercing. Some women without sore nipples also develop mastitis.

Mastitis causes an area of hardness, pain, redness and swelling in the breast. It often starts in a section of breast near to the nipple. You may also develop a high temperature and feel unwell, with flu-like symptoms.

A blocked milk duct sometimes occurs in breast-feeding women. A blocked milk duct also causes a painful, swollen area in a breast. The overlying skin is sometimes red and inflamed, but it tends to be not as bad as mastitis caused by an infection.<\p>

When you feed your baby, the pain may increase due to the pressure of milk building up behind the blocked duct. A blocked milk duct will usually clear within 1-2 days and symptoms will then go. However, in some cases a blocked milk duct becomes infected and develops into a mastitis. So, some cases of mastitis develop as a complication of a blocked milk duct, but some cases occur without a preceding blockage.<\p>

A blocked milk duct may clear more quickly by feeding your baby more often from the affected breast and gently massaging your breast whilst feeding.

Infective mastitis is usually treated with a course of an antibiotic. However, a mild case may go without any treatment. If you notice a tender swollen area in a breast when you are breast-feeding, it may be a blocked milk duct or a developing mastitis. It may be reasonable to 'see how it goes' over a day or so.<\p>

However, if your symptoms become worse you should see a doctor. After talking to you and examining you, they may prescribe an antibiotic. The infection will usually clear within a few days of starting the antibiotic.

Occasionally, an abscess may form inside an infected section of breast. This is thought to happen in fewer than 1 in 100 cases of mastitis. An abscess is a collection of pus that causes a firm, red, tender lump. The pus can be seen with an ultrasound scan. If the skin over the abscess is not broken, the pus can be drained with a needle and syringe. If the skin is broken (or very thin) it may be better to make a small cut to let the pus drain out.

  • If you are breast-feeding, continue to feed from the affected breast. This helps the milk to continue flowing and stops the breast from becoming engorged and making things worse. After each feed, try to express any remaining milk from the affected breast. Feeding from an infected breast does not harm the baby. If the baby swallows bacteria from an infected breast, the bacteria will be killed by the acid in the baby's stomach.
  • The doctor will choose an antibiotic that is safe to give to breast-feeding women and which will not harm the baby.
  • You can take simple painkillers (such as paracetamol or ibuprofen) to ease pain and reduce fever. Cold packs can also be quite soothing when placed on the breast.
  • A breast-feeding baby may refuse to feed from the affected breast, as the taste of the milk may change a little. If this occurs, feed from the other breast. Do remember to express the milk (that your baby has refused to take) from the affected breast. This will stop the breast swelling and becoming more painful. It will also keep up the demand for milk, so production does not slow down.

La Leche League (GB)

For mother-to-mother breastfeeding support from pregnancy through to weaning.
Helpline (24 hours) 0845 120 2918 Web:

Breastfeeding Network

Tel (supportline): 0844 412 4664 Web:

Association of Breastfeeding Mothers

Tel (breastfeeding helpline): 08444 122 949 Web:

Original Author:
Dr Tim Kenny
Current Version:
Peer Reviewer:
Dr Hannah Gronow
Document ID:
4840 (v39)
Last Checked:
Next Review:
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