Painful inflammation of breast tissue in part of one or both breasts

  • Age, genetics, and lifestyle are not significant factors

Inflammation of one or both breasts is called mastitis. The condition usually occurs in the first 6 weeks of breast-feeding. However, mastitis may also develop after this time if breast-feeding is stopped suddenly and the breasts become overfilled with milk (see Breast engorgement). Mastitis in women who are not breast-feeding may be related to smoking, which can cause inflammation of the milk ducts, resulting in discharge of fluid from one or both nipples (see Nipple discharge).

Mastitis is caused by infection of a blocked milk duct or an area of the breast that is inadequately drained of milk. The infection is commonly caused by the bacterium Staphylococcus aureus, which enters the breast through broken skin, most often on the nipple (see Cracked nipples). Mastitis affects up to 1 in 10 women who breast-feed. Women breast-feeding for the first time are particularly likely to develop the condition because they may not have learned how to position their baby correctly on the breast to make sure that the entire nipple is taken into the baby’s mouth, which will prevent the skin around the nipple from becoming cracked (see Avoiding cracked nipples).

What are the symptoms?

Mastitis usually affects only one area of a breast. Symptoms of the condition develop gradually over a period of several days and may include:

  • Tender, red area that spreads away from the nipple.

  • Swelling and pain in the affected part of the breast.

A severe, flu-like illness with fever and chills may also develop together with the breast inflammation.

If it is left untreated, inflammation of the breast gradually becomes worse and a pus-filled cavity, called a breast abscess, may develop, causing a firm lump that is painful to the touch. However, such breast abscesses are now relatively uncommon because antibiotics are usually prescribed at the first sign of an infection to destroy the bacteria before a breast abscess has had a chance to develop.

What can I do?

You should keep breast-feeding if you develop mastitis because stopping may cause the breasts to become engorged with milk and encourage an abscess to develop. However, you should check your breast-feeding technique with your breast-feeding counsellor. The infection will not harm your baby because the bacteria in your milk will be destroyed by the baby’s stomach acid. The regular flow of milk will help to keep your breast well drained and thereby prevent the condition from becoming worse. Any milk that still remains in the affected breast following breast-feeding should be expressed if possible.

A heat pad or a well-wrapped hot water bottle placed on the affected area of the breast may help to encourage the flow of milk and relieve the pain. Mild painkillers, such as paracetamol, may be useful to ease the discomfort. You should try to rest as much as possible and also try to drink plenty of nonalcoholic fluids.

If an abscess develops, you should not breast-feed with the affected breast. Instead, you should empty the breast of milk by gently expressing it with your hands or using a breast pump, a suction device that is designed to extract and collect milk from the breasts.


The red triangular area of inflammation radiating away from the nipple indicates mastitis, a condition that may develop in women who are breast-feeding.

What might the doctor do?

A diagnosis of mastitis is usually obvious from the symptoms, especially if you are currently breast-feeding your baby or if you have recently stopped breast-feeding. Your doctor will examine your breasts and may arrange for a sample of your milk to be sent to a laboratory in order to identify the bacteria that are causing the infection. He or she may also arrange for you to have ultrasound scanning to examine any lumps that may be present in the breast. Your doctor will probably prescribe a course of oral antibiotics to treat the infection.

Mastitis usually clears up within 2 or 3 days of beginning a treatment regimen with antibiotics but you should finish the entire course, even if your symptoms start to improve, in order to eradicate the infection. However, if a breast abscess has already developed, the pus that has collected may have to be drained from the breast, either under local or general anaesthesia. Once all the pus has been removed, a recurrence of the abscess is unlikely.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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