Black hair on both sides of the nose may be caused by genetic factors, hormonal abnormalities, taking medications and other reasons. 1. Genetic factors: black hairs on both sides of the nose may be caused by familial inheritance, if the parents have this condition, the children have a greater likelihood of experiencing this symptom. 2. Hormonal abnormalities: polycystic ovary syndrome will make the body androgen secretion exuberant, which can stimulate the growth of hair, which leads to body hair parts of the hair is long and black, will also cause the nose on both sides of the long black hair. 3. Taking drugs: It may also be due to inappropriate use of hormonal drugs, causing hormone level disorders in the body, androgen secretion, estrogen secretion, which can lead to the growth of black hair on both sides of the nose. It is recommended to go to the hospital in a timely manner, to clarify the cause of the disease, and then follow the doctor’s instructions for treatment.