Mastitis is a medical term for a red, swollen breast. If mastitis happens while you are breastfeeding it is extremely painful and usually caused by a bacterial infection.
Mastitis usually occurs when there is an abundant supply of milk for your baby's needs and usually in the first weeks after birth. It may be because there is a blocked duct which hasn't resolved.
Mastitis symptoms are similar to flu symptoms - you will feel hot, feverish and depressed. Your breast may also be red, swollen or tender and there are often red streaks on the sore breast.
With prompt treatment you may be able to avoid antibiotics through the use of warm packs, massage, rest analgesics, arm exercises and frequent breastfeeds. You may also wish to express. Make sure you keep breastfeeding and you will know if it has worked because the flu symptoms will start to disappear. If your treatment hasn't worked after 6-8 hours, you will need some medication.