Milk comes out of tiny holes on the tip of the nipple called nipple pores. Most women have about five to nine of these openings, though the range spans from as few as one to as many as 18. When milk flows, it exits from several pores at once, which means it doesn’t come out in a single stream. Instead, it sprays or drips in multiple thin streams going in slightly different directions.
How the Nipple Is Built
Inside each breast, milk is produced in clusters of tiny sacs called alveoli. From there, it travels through a branching network of ducts that converge as they approach the nipple, like tributaries feeding into a river. By the time they reach the base of the nipple, there are roughly nine main ducts (ranging from four to 18), each carrying milk toward its own opening on the nipple’s surface.
Not every opening you can see on the nipple actively delivers milk. Some ducts are too narrow or aren’t connected to functioning milk-producing tissue. Studies examining nipples during pumping found that only about five ducts were actively releasing milk on average, even when more openings were technically present. So while the nipple may have up to 20 visible pores, fewer than half typically produce milk at any given time.
What About the Bumps on the Areola?
The small raised bumps scattered across the areola (the darker skin surrounding the nipple) are not milk pores. These are Montgomery glands, which produce an oily substance that keeps the nipple and areola moisturized and protected. They become more prominent during pregnancy and breastfeeding, which is why some people mistake them for milk outlets. In rare cases, a tiny amount of milk has been observed seeping from these glands during manual expression, since some researchers consider them a type of accessory mammary tissue. But for practical purposes, all meaningful milk flow exits through the nipple tip itself.
How Milk Gets Pushed Out
Milk doesn’t flow continuously. It’s released in waves triggered by a hormonal reflex. When a baby latches and begins sucking, or even when a mother anticipates a feeding, the brain releases oxytocin. This hormone causes tiny muscle cells wrapped around the milk-producing sacs to squeeze, pushing milk down through the ducts and out the nipple pores. This is called the let-down reflex, and most women feel it as a tingling or tightening sensation in the breast.
Let-down can be forceful. During an active let-down, milk may spray outward in fine streams from multiple pores simultaneously. Some women experience an overactive let-down where milk sprays so quickly that it overwhelms the baby. In those cases, briefly removing the baby and catching the initial spray in a towel, or pressing gently against the side of the breast to slow the flow, can help.
How the Baby Draws Milk Out
A baby doesn’t just suck milk out of the nipple the way you’d drink through a straw. The process involves a coordinated wave of tongue movement. The baby latches onto not just the nipple but a significant portion of the lower areola, drawing the nipple deep into the mouth so it reaches the junction of the hard and soft palate. From there, the tongue rolls in a wave from front to back, creating suction that pulls milk from the ducts.
This is why latch depth matters so much. If a baby latches only onto the nipple tip, the tongue can’t compress the tissue beneath the areola where milk pools in the wider portions of the ducts. The result is a baby who works hard but gets little milk, and a mother with sore nipples. A good latch positions the nipple far back in the baby’s mouth, with more areola visible above the top lip than below the bottom one, and the chin pressing into the breast.
Breastfeeding and bottle feeding actually use different mouth mechanics. The breast’s ducted structure requires the baby to generate real suction to draw milk out. Bottle nipples, being hollow, allow babies to get milk primarily by compressing the nipple, which takes less effort. This difference is one reason some babies struggle to switch between breast and bottle.
When a Pore Gets Blocked
Sometimes a single nipple pore becomes clogged, creating what’s known as a milk bleb or milk blister. It looks like a small white or yellow raised spot on the nipple surface, caused by thickened milk or a thin layer of skin growing over the pore opening. A bleb can be quite painful, especially during nursing, because milk backs up behind the blockage and puts pressure on the duct.
Blebs are often linked to a shallow latch that doesn’t drain the breast evenly. They can also occur alongside a plugged duct deeper in the breast. Continued nursing often helps clear a bleb, since the baby’s suction can dislodge the blockage. Gently squeezing just behind the bleb after softening it with warm water may also express the thickened plug of dried milk. If a bleb persists or keeps returning, it usually signals a latch issue worth addressing.