Armpit hair is normal in 13-year-old girls, and is related to heredity and androgen level secretion. Armpit hair is the normal body hair of the human body, is the manifestation of secondary sexual characteristics, affected by the level of androgens in the body, the main function is to protect, promote sweating and so on. Armpit hair usually appears after puberty, so girls 13 years old long armpit hair is normal, but there are some people will not have armpit hair, mainly related to genetic factors. If a girl has dense armpit hair, consider the androgen level in the body is exuberant, if it does not cause physical discomfort and other symptoms, do not worry too much, is a normal phenomenon. If too much armpit hair causes psychological distress, you can consider removing armpit hair or laser hair removal. Armpit hair is generally normal for a 13-year-old girl, so don’t be too nervous and keep the area clean.