Black hair on the nose can be caused by heredity, excessive hormone secretion and other physiological factors, or consider acne, polycystic ovary syndrome and other diseases. 1. Physiological factors: Heredity, or excessive secretion of androgens, may lead to black hairs on the nose, if not accompanied by other uncomfortable symptoms, are normal phenomena, do not need to worry too much. 2. Acne: Acne is a chronic inflammatory disease of the sebaceous glands of the hair follicles, the cause of which is related to excessive sebum secretion, abnormal keratinization of the cells around the hair follicles, and overpopulation of Propionibacterium acnes. Patients may have blackheads and pimples, which are characterized by black hairs on the nose, and may be accompanied by pimples, pustules, nodules, cysts and other symptoms. 3. Polycystic Ovary Syndrome: The cause of polycystic ovary syndrome is not yet clear, and it may be caused by a combination of genetic and environmental factors. Patients may develop acne, hirsutism and other symptoms, manifested as black hairs growing on the nose. There are many causes of black hairs on the nose, and it is recommended that patients go to a regular hospital to find out the cause of the problem in a timely manner.