The long hair on the arms of 14-year-old girls is usually related to heredity, strong secretion of androgen, drug stimulation, other diseases and other conditions. 1. Heredity: 14-year-old girl arm hair long may be affected by genetic factors, if the parents have arm hair long situation, then their children may also appear arm hair long. 2. Androgen secretion: Androgen secretion can also lead to the situation of long arm hair, 14-year-old girl just in the puberty. 3. Drug stimulation: If a 14-year-old girl has taken hormonal drugs such as corticosteroids, it may also lead to long arm hair. 4. Other diseases: there are some diseases such as hyperadrenocorticism, pituitary tumors, etc., may also lead to 14-year-old girls with long arm hair. There may be other reasons why a 14-year-old girl may have long hair on her arms, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.