The causes of bleeding from breast pump suction are mucosal damage to the milk ducts, acute mastitis, nipple overflow. Damage to the milk ducts during breastfeeding is manifested by nipple cracking, redness, swelling, tingling, and lumps in the breast, leading to erosion around the nipple, and improper use of the breast pump can lead to local crusting off causing bleeding. The invasion of Staphylococcus aureus and streptococcus into the breast tissue and milk stagnation during lactation can lead to cracking of the nipple and areola area, causing local redness, swelling, heat, septic inflammation, and lumps, manifested as local lumps, pressure pain, and enlarged lymph nodes. Physiological or pathological factors can lead to nipple overflow. Pathological factors include papilloma, ductal dilatation, breast cancer, etc., mainly depending on the nature of the overflow, suggesting different diseases. Local bleeding can occur when using a breast pump due to swelling or purulent discharge from the nipple area.