What causes mastitis?

Mastitis is typically caused by bacterial infection or milk stasis – where milk is produced but remains in the breast.


Symptoms and complications may include, but are not limited to:

    • Warmth or heat in the breast tissue

    • Enlargement, redness, tenderness, or sensitivity of the breast

    • Generally feeling ill (malaise)

    • Lump(s) in the breast

    • Liquid or pus discharge

    • Fever

    • Feeling anxious or stressed

    • Shivering and chills

If left untreated, severe infections could lead to pus-filled cysts, called abscesses, within the breast tissue.


Mastitis usually occurs during breastfeeding when breast milk isn’t properly removed from the breast, but it also occurs when bacteria commonly found on the skin enters the nipple through small cracks. Staphylococcus aureus is often implicated. This form of mastitis is called “acute puerperal mastitis”.

“Chronic cystic mastitis”, on the other hand, is a different kind of mastitis that doesn’t involve inflammation.

The following are some of the factors known to cause mastitis:

    • Bacteria entering the breast – Bacteria from a baby's mouth or the mother’s skin surface can enter milk ducts through a break or crack in the nipple skin, or through a milk duct opening.

    • Blocked milk ducts – Milk ducts can clog if a breast is not emptied during feeding. This causes milk to back up, which can lead to infection.

    • Impaired immune system – If a mom experiences undue stress or fatigue, is anaemic, is not eating well or has diabetes or HIV, her resistance to infection is markedly reduced.

    • Tight clothes – A tight bra or tight upper-body clothing can restrict the flow of milk and may cause infection.

    • Irregular and missed breastfeeding – This causes breasts to become overfull, leading to engorgement, plugged ducts and, ultimately, mastitis.

    • Incorrect positioning – When a baby is not positioned at the breast correctly or is unable to suck efficiently, the milk flow is reduced. Plugged ducts and mastitis may follow.

    • Nipple piercing

    • Rapid weaning

The above are just some of the many causes of mastitis, and a woman may experience one or more of these causes at any time.

Who is at risk?

While mastitis commonly affects breastfeeding mothers, it can sometimes occur in women who are not breastfeeding, or who have never experienced childbirth.

And, although rare, men can also be affected by mastitis. Quite simply, the condition involves breast tissue, which men also have. Men with nipple piercings may be at higher risk of infection.

Prevalence rates

An observational study conducted in Australia, the USA, New Zealand and Finland has concluded that, across the board, between 20% and 25% of breastfeeding women will develop mastitis during the course of lactation, while about 20% to 35% of affected women will have recurrent episodes.


To confirm whether or not you have mastitis, a medical professional will conduct a physical examination while questioning you about your symptoms. Certain tests may be necessary for your doctor to get a better understanding of your condition.

If you’re lactating, it’s important to treat your mastitis so that you can continue breastfeeding your baby. The good news is that the mastitis usually doesn’t present a risk to your child. It should be noted, however, that mastitis does increase the risk of mother-to-child transmission of HIV.

Your doctor may also prescribe a diagnostic mammogram, and you may need a biopsy to make sure you don't have breast cancer.


Mastitis prevention usually involves the following:

    • Making sure your baby is well-latched. Seek help early if you’re experiencing problems.

    • Feeding your baby as long and as often as he/she wants to. This ensures that your breasts are well drained.

    • Not skipping a breastfeed (for instance, giving your baby a bottle of formula instead of breastfeeding)

    • Avoiding tight clothing

    • If you have a lump in your breast, massage it well while your baby is feeding or in the shower. Seek help if you’re unable to clear the lump within a day.

    • Self-care such as drinking extra fluids, eating well and resting


If you’ve been diagnosed with mastitis, treatment will entail:

    • Continuing to breastfeed, ensuring that milk is removed effectively. It’s important to note that to wean your baby at this stage will only aggravate the mastitis.

    • Possibly expressing milk after a feed if your baby hasn’t completely emptied the breast.

    • Gently massaging the affected breast as your baby feeds. This will help to empty the breast.

    • Getting rest. It’s important to get someone to help in and around the home while you recover.

    • Your doctor may prescribe antibiotics such as dicloxacillin, ciprofloxacin or cephalexin over a 10-14 day period and completing the course.

    • Pain relievers such as acetaminophen or ibuprofen can help as you wait for the antibiotics to work.

    • Application of heat or cold to the affected breast can also be effective. (A cloth soaked in warm water applied before feeding and a cloth soaked in cold water after feeding.)

Check in with your doctor if your mastitis doesn't clear up after completing your course of antibiotics.

If an abscess forms, surgical drainage may be necessary. As inflammatory breast cancer can present with some of the same symptoms, your doctor might also perform a biopsy to rule out this possibility.

When to see a doctor

You should call your health-care provider as soon as you feel any suspicious lump or display any of the symptoms listed above. This is recommended whether you’re breastfeeding or not.

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