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Mastitis is an inflammation of the breast, usually caused by a build-up of milk within the breast in women who are breastfeeding. It is a painful condition of the breast, which becomes red, hot and sore (inflamed). Sometimes it becomes infected.

Mastitis can be either:

  • Non-infectious - when the build-up of milk irritates the breast tissue, making it become red, hot and swollen (inflamed).
  • Infectious - when the build-up of milk becomes infected and the infection spreads to the breast tissue. The infection is caused by germs (bacteria) which may have come from the skin.

If non-infectious mastitis is not treated, it can become infectious mastitis. You can't tell which type of mastitis it is from looking at it, and the treatment is the same.

You are most likely to develop mastitis if you are a woman who is breastfeeding. It is sometimes called 'puerperal mastitis' or 'lactational mastitis'. It typically develops within the first few weeks of breast-feeding. Read about lactational mastitis.

Mastitis sometimes occurs in women who are not breastfeeding (non-lactational mastitis). Germs (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 but it can happen when you don't have any problems with your nipples. Smoking can be a trigger because nicotine damages the ducts in your breasts.

The rest of this information just deals with non-lactational mastitis.

Mastitis causes an area of hardness, pain, redness and swelling in the breast and makes you feel generally unwell. It often starts in a wedge-shaped section of breast. It usually occurs in one breast only.

You also develop a high temperature (fever) and feel like you are coming down with flu. Other symptoms might include muscle pains, headaches and feeling tired and low.

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If you are not breastfeeding, mastitis may need to be treated with a course of an antibiotic. However, a mild case may get better without any medical treatment. 

The following measures may help to treat your mastitis without the need for antibiotics:

  • Avoid tight-fitting bras.
  • Try to eat well and drink plenty of fluids.

However, if your symptoms become worse you should see a doctor. After talking to you and examining you, they may prescribe an antibiotic. They may suggest that you wait 24 hours before starting the antibiotics, if your symptoms are mild or have only just begun. The mastitis will usually clear within a few days of starting the antibiotic.

Occasionally, an abscess may form inside an infected section of breast. An abscess is a collection of pus that causes a firm, red, tender lump. This is thought to happen to between about 3 and 7 women with mastitis, out of every 100. If this happens to you, you will need to go to hospital for treatment.

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 by a doctor. If the skin is broken (or very thin) the doctor may need to make a small cut to let the pus drain out.

Breast Pain

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Further reading and references

  • Salzman B, Fleegle S, Tully AS; Common breast problems. Am Fam Physician. 2012 Aug 1586(4):343-9.

  • Spencer JP; Management of mastitis in breastfeeding women. Am Fam Physician. 2008 Sep 1578(6):727-31.

  • Cheung KL, Lam TP; Approach to a lump in the breast: a regional perspective. Asian J Surg. 2005 Jan28(1):65-70.

  • Goyal A; Breast pain. Clin Evid (Online). 2011 Jan 172011. pii: 0812.