What Causes Hair on the Arms to Grow in a Woman?

According to the American Society for Aesthetic Plastic Surgery, women in the U.S. sought over 1.2 million laser hair removal procedures in 2007 4. Although most of the women's hair-removal industry focuses on leg, bikini and underarm hair removal, many women also feel self-conscious about the hair on their forearms. Several conditions can cause excess arm hair growth in a woman, and they all have to do with hormones.


For most women, hair begins to grow on the arms -- in addition to other places -- during puberty. In adolescence, around the ages of 8 to 13, the brain releases a hormone that triggers the pituitary gland to release two more puberty hormones, one of which is a follicle-stimulating hormone that signals to the body to begin growing hair. If you're not used to having any hair on your arms and it suddenly appears, you may feel like it's very conspicuous; however, hair growth on the arms is completely normal and probably isn't as noticeable as you think.


The hormonal changes that happen during pregnancy can also cause excess arm hair growth. Some pregnant women may see more hair growing on their arms, as well as on their faces and/or chests. This is a normal side effect of pregnancy, and the hair should go away within six months after giving birth. Although extra arm hair growth is normal, a lot of excess hair growing quickly on the face, chest and abdomen may be a sign of a problem; talk to your doctor if you see this happening or if you have any other concerns.

Polycystic Ovarian Syndrome

Another hormonal issue, polycystic ovarian syndrome or PCOS, can cause excess arm and body hair growth 2. Women with PCOS have excess levels of androgens, or male hormones. Though it's normal for women to have these hormones, high levels of them can cause problems in the reproductive system. Along with excess body hair, other symptoms of PCOS include:

  • trouble conceiving a child
  • irregular menstrual periods
  • cysts on the ovaries
  • weight gain
  • dark patches on the skin

See a doctor if you have any of these symptoms; treatment is available to reduce the male hormones your body is producing.


Excess arm or body hair growth, called hirsutism, is a symptom or side effect of pregnancy and PCOS but is also itself a disorder. Other symptoms of hirsutism include a deepening voice, reduction in breast size and increased muscle mass. Your doctor can determine if you have hirsutism and recommend medications to balance the hormones in your body, as well as treatments to remove excess hair.