Girls chest long hair may be physiological factors, may also be polycystic ovary syndrome or local drug triggered. 1. physiological factors: normal people all over the body except palm and plantar skin can appear hair, but the chest is generally cui hair, generally fine, soft, short, and skin color consistent, belong to the normal physiological structure, no need to deal with. 2. Polycystic ovary syndrome: polycystic ovary syndrome is a common reproductive endocrine disease, can cause menstrual irregularities, hairy, so if there is an abnormal increase in chest or other body parts of the hair thickening, you need to go to the hospital, improve endocrine related examinations and uterine accessories ultrasound. 3. Local use of drugs: If the local long-term external glucocorticoid drugs can cause hormone-dependent dermatitis, local hair growth, skin atrophy, capillary dilatation and other adverse reactions. You can go to the hospital for further examination to clarify the specific cause of the disease, and deal with the cause of the disease.