Mastitis is an infection of the breast tissue that results in breast pain, swelling, warmth and redness. You also might have fever and chills. Mastitis most commonly affects women who are breast-feeding (lactation mastitis), although sometimes this condition can occur in women who aren't breast-feeding. In most cases, lactation mastitis occurs within the first six to 12 weeks after giving birth (postpartum), but it can happen later during breast-feeding. The condition can cause you to feel run down, making it difficult to care for your baby.
Try applying moist heat a few times a day, and nurse your baby frequently to keep the affected breast empty. (This may also help clear up any infection more quickly.) In the meantime, you can take ibuprofen to ease the pain. If your symptoms don't improve within 24 hours of trying these measures, see your healthcare provider. She may prescribe antibiotics, rest, and pain relievers in addition to hot compresses.
Early stages of mastitis can present with local pain, redness, swelling, and warmth. Later stages also present with systemic symptoms like fever and flu-like symptoms and in rare cases an abscess can develop. However it is pretty common that symptoms develop very quickly without any warning. Except in severe cases it is not necessary to wean a nursling because of mastitis; in fact, nursing is the most effective way to remove the blockage and alleviate the symptoms. Sudden weaning can cause or exacerbate mastitis symptoms and cause hyponatremic shock in the infant.