Dark armpit hair is a normal manifestation. If it is accompanied by dark armpit skin, it is considered to be related to hyperpigmentation, changes in hormone levels, acanthosis nigricans and other factors. 1. Normal performance: with age, to puberty, the armpit may appear some hair. The hairs are usually darker, which is a normal physiological manifestation and usually does not need special treatment. 2. Accompanied by black armpit skin: black armpits are considered and the body melanin increase, resulting in local pigmentation. In addition, the hormone level changes after pregnancy, such as the increased secretion of estrogen and progesterone, may lead to local pigmentation and deepening of skin color. In addition to this, acanthosis nigricans leads to hyperkeratosis and hyperpigmentation of the skin, which can also lead to localized darkening of the color. If there is no other discomfort, it is recommended to observe closely and pay attention to local hygiene, and generally no special treatment is needed. If accompanied by armpit skin darkening, it is recommended to go to the dermatology department of the hospital in a timely manner to clarify the cause and then treat the cause.