If a breastfeeding woman has a blockage of milk that forms a hard lump, it will lead to breast swelling and pain, and when mastitis develops, it can cause obvious redness, swelling, heat and pain, and even fever, chills and other systemic manifestations, and in severe cases, it may also cause septicemia. The reason for this is that there are a number of reasons why the milk ducts are not clear, the milk is stagnant, and if there is no bacterial infection, the pressure in the milk ducts is too high, which will cause a feeling of swelling and pain. When the milk is stagnant and bacteria invade, it can cause mastitis, and the patient can show the typical symptoms of infection such as redness, swelling, heat and pain at the hard lump, and in serious cases, the local area can become pus and form abscesses, and the patient can gradually develop fever, infection, fatigue and other systemic manifestations, and if the infection is serious, it may further develop into septicemia, which can jeopardize the patient’s life. It is recommended that patients seek medical attention in time and have their mammary glands unblocked by a professional physician. If mastitis occurs, antibacterial drugs should be given under the guidance of the physician to fight infection.