When breastfeeding, if there is pain on one side of the breast and not on the other, the most common reason is an inflammatory reaction on the painful side. During breastfeeding, there is a large amount of milk filling the breast, so if there is improper care or squeezing, it will cause a local inflammatory reaction and local pain. It is recommended to use hot compresses to promote the absorption of inflammation, and if the milk is stagnant, try to make the milk drainage, so that the pain will be reduced, and if necessary, go to the hospital to give anti-inflammatory treatment. If the local inflammation is not controlled, there is a risk of localized septicemia, which will eventually be treated by incision and drainage, causing a lot of pain.