Mastitis is an inflammation of breast tissue that sometimes involves an infection. The inflammation results in breast pain, swelling, warmth and redness. You might also have fever and chills.
Mastitis most commonly affects women who are breast-feeding (lactation mastitis). But mastitis can occur in women who aren't breast-feeding and in men.
Lactation mastitis can cause you to feel run down, making it difficult to care for your baby. Sometimes mastitis leads a mother to wean her baby before she intends to. But continuing to breast-feed, even while taking an antibiotic to treat mastitis, is better for you and your baby.