Hair on the breasts may be caused by physiological reasons, genetic factors and polycystic ovary syndrome. 1. Physiological reasons: Breast hair growth is usually a normal physiological phenomenon, everyone has hair follicles around the nipple, the nipple will start to grow hair during the developmental period, and breast hair usually grows around the areola. 2. Hereditary factors: If both parents are hairy, the hair of their children may be hairy, which may lead to the phenomenon of hairy breasts. 3. Polycystic Ovary Syndrome (PCOS): Due to ovarian disease, the level of androgen in the body is too high, resulting in the inability of normal ovulation, which in turn leads to the phenomenon of hairy breasts. At the same time, it can also be accompanied by an increase in armpit hair, leg hair, thicker phenomenon, and may even appear beard. In addition, taking certain drugs can also lead to hair on the breasts, when the patient has hair on the breasts, excluding physiological reasons and genetic factors, should consult a doctor in time, ask the doctor to clarify the cause of the disease, and if necessary, to carry out appropriate treatment.