What causes a blocked milk duct?

A longer-than-usual gap between feeds, sudden weaning, a change in the baby's feeding pattern, or pumping more or less than usual can upset the balance between milk production and removal. A shallow latch or poorly fitting pump flange may make milk removal less effective. Pressure from a tight bra, a bag strap, or sleeping position can irritate a particular area. Oversupply may contribute because the breast makes more milk than is being removed. Sometimes there is no single clear trigger.

Return to a comfortable, responsive feeding rhythm rather than adding repeated pumping sessions. Check that bras and clothing do not leave deep marks, and vary any position that presses on one part of the breast. If pumping hurts, review flange fit and suction rather than increasing suction strength. A lactation professional can observe a feed and help identify latch, supply, or equipment issues. Cooling the tender area and avoiding forceful massage can calm inflammation while milk continues to move.

Seek prompt medical advice if the breast becomes increasingly red, hot, swollen, or painful, or if fever, chills, pus, or flu-like symptoms appear. A persistent or recurring lump should be examined even when you otherwise feel well. These features can point to mastitis, an abscess, or a breast problem unrelated to milk flow, and the next step depends on an examination.

Ask whether your feeding pattern, milk supply, pump settings, or flange size could be involved. Mention medicines, previous breast surgery, nipple damage, and repeated inflammation. If episodes recur, ask whether another diagnosis or imaging should be considered.