Mastitis (breastfeeding) 

Mastitis is a condition that causes the breast tissue to become painful and inflamed (red and swollen). As it usually occurs in women who are breastfeeding, it is often referred to as lactation mastitis or puerperal mastitis.

See the Health A-Z topic about Non-breastfeeding mastitis for more information about mastitis in women who are not breastfeeding.

Mastitis usually only affects one breast. Some women may also experience flu-like symptoms such as:

• high temperature (fever) of 38C (100.4F) or above
• chills
• aches

Types of mastitis

There are two main types of mastitis:

• non-infectious mastitis, which is usually caused by breast milk remaining within the breast tissue (milk stasis) as a result of a blocked milk duct or problems with breastfeeding
• infectious mastitis, which is usually caused by bacteria

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

How common is mastitis?

Around one in 10 women who are breastfeeding are affected by mastitis. Most women will develop mastitis during the first three months after giving birth.

Continue breastfeeding

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

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

The milk from the affected breast can be a little saltier than normal, but it is safe for the baby to drink. Any bacteria that is present in the milk will be harmlessly absorbed by the baby's digestive system and cause no problems.

Outlook

Most cases of mastitis can be successfully treated using self-help measures, such as resting and drinking plenty of fluids and by adjusting the technique being used to breastfeed. It is important to ensure that the baby is properly attached to the nipple and that the breast is empty after the feed. In some cases it may be necessary to:

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

Expressing breast milk means that you encourage it to flow by hand or using a pump.

Infectious mastitis requires prompt treatment to prevent more serious complications developing in the breast, such as an abscess (a painful collection of pus). More serious cases of infectious mastitis will require antibiotics in order to bring the infection under control.