Mastitis is generally considered to be caused by the accumulation of milk, which occurs during breastfeeding when the posture or unintentional actions by the child cause damage to the milk ducts, leading to an accumulation of milk within them. Since milk serves as an excellent culture medium, this can lead to bacterial infection. The second point is that if there are cracks or fissures on the nipple, bacteria can infect in reverse, leading to significant infections by Staphylococcus aureus, which can also cause mastitis. The third point concerns a weakened immune system, for example due to mental stress or lack of sleep. These are the main causes of acute mastitis.