Symptoms of mastitis can include breast swelling, fever and chills, breast tenderness or warmth, malaise, redness of the skin of the breast, and fever, notes the Mayo Clinic. A lactating woman may feel pain while breastfeeding or see pus or blood in her milk, according to MedicineNet.
Mastitis usually begins with pain in part of one breast, as Kaiser Permanente explains. Body aches may be present. Indications of a worsening infection may include flu-like symptoms that increase in severity, an accelerated heart rate and swollen lymph nodes in the armpit on the same side as the affected breast.
One possible complication of mastitis is a breast abscess, according to WebMD. The abscess is usually a well-defined mass that feels tender. The presence of such a mass, a persistent fever and pus drainage from the nipple are all possible signs that the patient has a breast abscess.