If a woman is pregnant or breastfeeding and has no other discomfort, it may be a normal physiological phenomenon to squeeze out yellow liquid from one breast. If the physiological phenomenon is excluded, it may be caused by acute mastitis, cystic hyperplasia of the breast and other diseases. 1. physiological phenomenon: one side of the breast extrusion of yellow liquid, common in pregnancy and lactation of women, if the patient’s body lactogen increase, will lead to nipple overflow symptoms. No no. In addition, teenage female body development, endocrine disorders can also lead to nipple discharge. In daily life, patients are advised to keep the area around their breasts clean and eat a reasonable diet. 2. Acute Mastitis: Acute mastitis is mainly caused by the accumulation of milk in one breast, usually accompanied by yellow liquid, local redness, swelling, pain and other symptoms, common patients are breastfeeding women. It is recommended that the patient needs to drain the breast milk, keep the local area clean, take oral cefdinir antibiotic treatment, and if an abscess has been formed, it should be incised and drained as soon as possible. 3. Breast cystic hyperplasia: Breast cystic hyperplasia may be caused by excessive secretion of estrogen or secretions blocking the lumen, which usually results in pain, nipple overflow, and yellow fluid. For such patients, it is recommended to take anti-estrogenic drugs such as ethinyl estradiol and bromocriptine under the guidance of a doctor and undergo surgery if necessary. One side of the breast extrusion of yellow fluid should also be considered breast duct papilloma and breast cancer, excluding the normal physiological phenomenon, it is recommended that patients go to the hospital in a timely manner to identify the cause of the disease and timely treatment.