Nearly 1 in 5 breastfeeding women are affected by mastitis in the first 6 months. It usually develops in the first 3 months after giving birth. Doctors often refer to it as ‘lactation mastitis’ or ‘puerperal mastitis’.

What are the symptoms of mastitis?

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

If you're breastfeeding, they may ask you to demonstrate your technique.

Even if it is painful to feed, this is not a time to wean. You need to keep your breast as empty as possible, and your baby sucking is the best way to do this. The milk is safe for your baby to drink.

What causes mastitis?

Mastitis is inflammation (swelling) of the breast tissue that 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 your nipples are cracked or sore or, in non-breastfeeding women, because of a 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.

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 paracetamol or ibuprofen, 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
• using a cold pack, such as a packet of frozen peas wrapped in a cloth, after a feed to help reduce pain and swelling

Breastfeeding advice

Feed more often than usual, starting each feed on the sore breast. Make sure the breast is drained well — but make sure the other breast doesn’t become too full, as that could cause mastitis on that side too.

Following the advice outlined below should improve your symptoms.

• Drain the affected breast often but gently. 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.
• 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, lactation consultant or child health nurse 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 before a feed can help with the letdown, making it easier for your baby to feed.
• Shift feeding positions to help shift the blockage.
• Make sure you eat well, and get enough rest.

Infectious mastitis

Infectious mastitis will need to be treated using a combination of the above techniques and antibiotics (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). 

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 concerning risk to your baby.

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.

Complications of mastitis

Mastitis should be promptly treated to prevent more serious complications developing, such as a breast abscess (a painful collection of pus).