There are many reasons why one side of the breast can squeeze out yellow water, such as breast cystic hyperplasia, acute mastitis, breast cancer and so on. 1. Breast cystic hyperplasia: Breast cystic hyperplasia is mainly due to the secretion of blocked ducts, estrogen secretion, can appear in the unilateral or bilateral, can show that one side of the breast can be squeezed out of the yellow water, accompanied by the touch of the lump, press the pain and other symptoms. 2. Acute mastitis: Acute mastitis is usually due to infection, and can be accompanied by redness, swelling, pain, fever, chills and other symptoms. 3. Breast Cancer: Breast cancer can be caused by yellow water coming out of one breast, which can be diagnosed through breast ultrasound, mammogram, and crude needle puncture. One side of the breast can squeeze out yellow water may also be intraductal papilloma, it is recommended that patients go to the hospital in time to improve the examination, take standardized treatment in accordance with the doctor’s instructions, do not ignore the symptoms, take it lightly.