Mastitis is an inflammation of the breast that occurs most commonly in breast-feeding women; it can be related to tissue injury, infection, or both. Breast-feeding mastitis is typically caused by bacteria that enter the breast through a cracked or sore nipple.

Signs of infection may include:

• Increased pain, swelling, redness, or warmth in an area on a breast.
• Red streaks extending from a breast.
• Drainage of pus coming from a breast.
• Swollen lymph nodes in the neck or armpit.
• Flu-like symptoms, such as fever of 101°F (38.5°C) or higher, chills, and fatigue.

Treatment usually involves antibiotic medicines, keeping up milk flow, and measures to relieve discomfort. While they are being treated, most women can safely continue to breast-feed or pump breast milk.