What happens if I get mastitis or a breast infection?

If not treated early and properly, this can lead to an abscess. Mastitis can occur in the second or third week of nursing; the breast becomes red, hot, and tender, with one-sided swelling, a temperature as high as 101° F, and flu-like symptoms. Treatment should include nursing on the unaffected side first. Treatment with antibiotics, heat, fluids, and a pain reliever such as Tylenol or Advil is also helpful.