9-year-old children’s body hair, most of the normal physiological phenomenon, but may also be some drugs, diseases caused by pathological phenomena, such as adrenal cortex hyperplasia. 1. Physiological phenomenon: with the growth and development of faster, as well as the improvement of living standards, the general 9-year-old girl began to enter puberty, body hair is a normal physiological phenomenon, no need to worry too much. The length and density of body hair can be affected by genetic factors, and there are individual differences. 2. Abnormal phenomena: (1) Drug factors: such as long-term use of hormones or external glucocorticoids patients, may appear abnormal body hair growth phenomenon. (2) Adrenocortical hyperplasia: 9-year-old children’s body hair growth may be caused by adrenocortical hyperplasia resulting in increased secretion of testosterone hormone. 9-year-old children body hairy, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.