Symptoms of a breast infection may include:

• Increased pain, swelling, redness, or warmth around a breast.
• Red streaks extending from a breast.
• Drainage of pus from a breast.
• Fever.

Mastitis is an inflammation of the breast that occurs most commonly in breast-feeding women. It may be caused by breast engorgement, a blocked milk duct, or cracked skin on the woman's nipples that allows bacteria to enter the breast. In women who are not breast-feeding, it is related to changes that can occur with aging, such as expanded (dilated) or irregular milk ducts.

Mastitis will not go away without treatment. Most women can safely continue to breast-feed or pump breast milk while being treated. Treatment usually involves a combination of antibiotics and home treatment to increase the flow of milk through the breast and relieve discomfort while the infection clears up. In some cases, a breast abscess may form, which is a pocket of infection. An abscess may need to be drained by a doctor, and the woman may need to stop breast-feeding for a few days while the infection is treated.

A breast infection can occur in a woman who is not nursing after an injury, such as a cut or bite to the breast, and sometimes without an injury. The term mastitis is sometimes used to refer to any noncancerous, inflammatory condition of the breast.

Breast infections never lead to breast cancer, but some breast cancers look like infections.