Anything that stops the breast from emptying completely is the primary cause of clogged milk ducts. This might be caused by a sports bra that is excessively tight or by having too few frequent feedings. Even the way you feed your infant might result in clogged ducts and mastitis. When breast milk is not frequently eliminated, it can build up and cause a blockage. Additionally, a nipple bleb may restrict the milk channel. When the body produces too much milk, the breast may become engorged and get blocked. Additional causes include exhaustion, excessive activity, dehydration, and weaning.