Mastitis is a breast infection - the infection of the breast tissue. Mastitis is a bacterial infection that occurs when harmful bacteria infiltrate the breast tissue through a breached area of the nipple skin such as a scratch and/or cracks, then multiply within the fatty tissue of the breast. The bacteria may also enter the breast tissue through the small holes in nipple’s milk ducts. In most cases the source of harmful bacteria (Staphylococcus aureus) is the surface of skin or the mouth of baby. After the bacteria infiltrate the body, it is multiplied causing redness and localized swelling of the breast and pain.
Mastitis usually only affects one breast and the symptoms often develop quickly.
Mastitis will not go away without treatment. If you have mastitis symptoms, you may need to call your doctor today. Prompt treatment helps keep infection from rapidly getting worse and usually improves symptoms after about 2 days.

Mastitis treatment
Treatment for mastitis usually includes:

• Oral antibiotics to destroy the bacteria causing the infection
• Regularly emptying the breast well by breast-feeding or pumping breast milk. Adequate emptying of the affected breast helps prevent more bacteria from collecting in the breast and may shorten the duration of the infection.

You can safely continue breast-feeding your baby or pumping breast milk to feed your baby during illness and treatment. Your baby is the most efficient pump you have for emptying your breasts. Your breast milk is safe for your baby to drink, because any bacteria in your milk will be destroyed by the baby's digestive juices.