During the onset of acute mastitis, symptoms often include high fever and chills, and the affected breast may enlarge and become firm, with throbbing pain that becomes more apparent during breastfeeding. This is usually accompanied by an increase in local skin temperature, redness and swelling, and tenderness. If the area softens over a short period, an abscess may have formed. If the infection is not controlled, it can lead to systemic infection or sepsis. Patients often have swollen lymph nodes, and blood tests show elevated neutrophil counts in white blood cells.