Milk ducts in the breast may become blocked during breastfeeding when the breasts are full and not emptied regularly or thoroughly. Blocked milk ducts cause a lump that is sometimes tender and can become infected (mastitis).

Blocked milk ducts may be treated by:

• Breastfeeding more often and in different positions, which helps drain milk from all parts of the breast.
• Breastfeeding from the affected breast first, to move milk through the breast faster.
• Applying moist heat to the area just before breastfeeding and hand-expressing or pumping a small amount of milk.
• Massaging the area, always working toward the nipple, to increase the flow of milk before and during breastfeeding.