When a milk duct is blocked, milk backs up behind the clog and raises pressure inside the duct. That pressure can irritate the duct lining and tiny capillaries in the breast tissue. If a small capillary breaks, a little blood can mix with your milk—often pink, red, or “strawberry” tinged. You might also see a stringy, rusty, or brownish color if older blood is present. This is different from blood due to a cracked nipple (which comes from the surface of the skin rather than inside the duct). The