Mastitis is inflammation of the breast tissue that causes pain, swelling and warmth, sometimes with an infection. It most often affects people who are breastfeeding, usually in the first weeks or months after birth.
Mastitis usually starts when milk builds up in the breast faster than it is removed. Missed feeds, a baby who has trouble latching, or pressure from a tight bra can all contribute. Bacteria can also enter through a cracked or sore nipple and cause an infection. Mastitis can happen in people who are not breastfeeding too, but this is less common.
Common symptoms include a swollen area on the breast that feels hot and painful, a wedge-shaped lump or hard area, and a burning pain that may be constant or only during feeds. Some people also get flu-like symptoms such as aches, chills and a high temperature.
NHS advice includes continuing to breastfeed or express, resting and drinking plenty of fluids. Contact a GP, midwife or health visitor if symptoms do not improve within 24 hours, if they get worse, or if you feel very unwell. A doctor may prescribe antibiotics.
Going back to work while breastfeeding can mean longer gaps between feeds, which can lead to milk build-up. A clean, private space to express, regular breaks and somewhere to store milk can make it easier to keep to a routine.
Sources: NHS, MedlinePlus.