A clogged (or blocked) milk duct occurs when milk can’t flow freely through one of the small ducts in the breast. These ducts carry milk from the breast tissue to the nipple. If milk backs up—often due to pressure, inflammation, or swelling in the surrounding tissue—it can create a sore, tender lump.

Signs of a clogged duct

A blocked milk duct often feels like a firm, painful lump under the skin. The area may appear red and feel sore when touched. Other common clues include:

Discomfort or pain when your milk lets down.

Localized swelling near the lump, rather than across the entire breast.

The lump shrinking or softening after a feeding or pumping session.

Relief from pain once milk flows again.

Sometimes, a small white spot—often called a milk blister—can appear on the nipple when a duct is blocked.

Why ducts become blocked

Milk can back up and cause a blockage for many reasons, such as:

Going long stretches without nursing or pumping.

Skipping regular feeds or suddenly changing your baby’s feeding schedule.

An ineffective latch that leaves milk behind in the breast.

Natural changes when weaning or starting solids.

Though rare, ducts can also become blocked when you’re not breastfeeding, due to certain breast conditions that cause fluid to collect.

How to tell if it’s a clogged duct

Most parents recognize a blockage based on symptoms alone. If you’re breastfeeding or pumping and notice a painful lump that eases after feeding, it’s likely a clogged milk duct. However, if you also develop fever, chills, or feel unwell, call your healthcare provider—these can signal an infection such as mastitis.

At-home care

Most blockages clear within a day or two with simple measures:

Continue nursing or pumping on your usual schedule—don’t overfeed or overpump, as this can worsen swelling.

Ease the pain and swelling with cold compresses and over-the-counter pain relievers (if your healthcare provider says they’re safe for you).

Gentle massage can help move fluid—think of softly stroking the breast toward your armpit or collarbone rather than deep, firm pressure.

Support lymphatic drainage by resting and avoiding tight clothing or underwire bras.

You’ll know the duct has cleared when the lump disappears and milk flows normally; sometimes you might even notice a thicker piece of milk as the blockage releases.

Possible complications

If left untreated, a clogged milk duct can lead to mastitis, which may cause fever, body aches, significant redness across the breast, and sharp pain during nursing or pumping. Mastitis needs prompt medical treatment, often with antibiotics.

Prevention tips

To help avoid recurring blockages:

Feed or pump on a regular schedule so your breasts are well-drained.

Ensure your baby is latching effectively and fully emptying the breast.

If you’re reducing feeds during weaning, express just enough milk for comfort so your body adjusts gradually.

Some parents find that maintaining overall breast health—through proper fit of bras and avoiding prolonged engorgement—also helps.

When to seek medical advice

Contact your doctor or lactation consultant if:

The lump does not improve after a couple of days of home care.

You develop fever, chills, or flu-like symptoms.

You experience worsening pain or notice significant redness or discharge.

Bottom line

A clogged milk duct can be uncomfortable, but with gentle care and continued feeding or pumping, it usually resolves quickly. Prompt attention and good breastfeeding habits help prevent it from developing into something more serious.