A clogged duct (blocked duct) is a localised blockage in a milk-carrying channel of the breast, causing a small tender lump that can lead to mastitis if left unresolved.
A clogged or blocked milk duct occurs when one of the segments of the breast is not drained properly during a feed, causing milk to accumulate in that channel. The NHS describes the result as "a small, tender lump in your breast". The blockage can also result from external pressure on the breast from tight clothing, a bag strap, or an ill-fitting bra. The NHS advises that dealing with a blocked duct quickly is important because, if left unresolved, it can lead to mastitis.
What causes a clogged duct?
According to NHS guidance, a blocked duct can develop if a breast segment is not drained properly during feeding — often because the baby is not attached to the breast correctly. It can also arise from a build-up of milk caused by skipping or delaying a feed, or from something putting external pressure on the breast such as a tight bra or bag strap. La Leche League GB notes that making significantly more milk than the baby needs, sudden reduction in milk removal, and rapid weaning are also contributing factors.
What are the symptoms?
The NHS describes a blocked duct as producing "a small, tender lump in your breast". La Leche League GB describes the affected area as feeling "warmer, harder, or more lumpy than usual", and the overlying skin may appear red or darker depending on skin tone. The breast as a whole may feel more uncomfortable than usual but systemic symptoms such as fever are not typically present at this stage; their development may indicate progression to mastitis.
How is a clogged duct managed?
NHS guidance recommends continuing to breastfeed frequently from the affected breast, avoiding tight clothing and bras so that milk can flow freely, applying warm compresses, and gently massaging toward the nipple during feeding. Cold compresses between feeds can also help with discomfort. La Leche League GB suggests taking standard doses of an over-the-counter anti-inflammatory such as ibuprofen and experimenting with different feeding positions. If symptoms persist or worsen, or if flu-like symptoms develop, the NHS advises contacting a GP as antibiotics may be needed.
Mastitis and clogged ducts — words that strike fear in every breastfeeding mother. What to do at the first sign, and when to escalate.
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