You probably don’t give a second thought to the hair on your scalp, legs, or arms. For that matter, you may not perceive how different types of hair grow on different parts of your body. But if you look closely at areas of your body that appear hairless — such as your ear lobe or forehead — you’ll likely spot tiny hairs. These are vellus hairs, also referred to as peach fuzz or baby hair. This hair is translucent and unmistakably thinner than other hair on your body.

You’ll also find these tiny hairs on your nose and eyelids. But in most cases, vellus hairs don’t appear on the soles of people’s feet or the palms of their hands. Although these hairs are common on adults, children have a larger number.

Vellus hairs may seem unnecessary, yet they serve a useful purpose. They regulate your body temperature and help sweat evaporate from your body.

Body hair undergoes various changes as you become older. Vellus hair is replaced with thicker hair in certain areas of your body during puberty. When this transition occurs, vellus hairs become terminal hairs.

The structure of terminal hair is different from that of vellus hair. It’s stronger, longer, and more noticeable. For example, prior to puberty a young man may have vellus hair on his chin and face, and above his lip. As puberty begins, these hairs change to terminal hair and become longer and stronger. This is when males develop facial hair like a mustache or beard.

Other areas on your body where vellus hair becomes terminal hair include your:

  • chest
  • abdomen
  • legs
  • arms
  • pubic area
  • feet

This changeover results from an increased production of a hormone called androgen. Androgen is natural to males and females, but males have a higher level. Therefore, men typically have more terminal hairs than females.

Keep reading: How to grow hair faster »

The amount of vellus hair on an adult varies from person to person. Due to genetics, some people maintain a larger amount of these tiny hairs after puberty. Some conditions do spur vellus hair growth. On that account, speak with your doctor if you notice an increase in vellus hairs on your body.

Cushing’s syndrome is a condition in which your body produces too much of the hormone cortisol. Symptoms may include:

  • weight gain
  • purple stretch marks
  • acne
  • slow-healing wounds

In women, this hormonal imbalance can also trigger an increase of vellus hairs on their face and body.

Males and females who have anorexia nervosa may also have a higher percentage of vellus hair. Anorexia is an eating disorder. Those with this disorder refuse to eat or eat very little to avoid weight gain. Anorexia can cause people to not receive enough nutrients from their diet. This deficiency can interfere with their body’s ability to change vellus hair to terminal hair.

Because of a hormonal imbalance during pregnancy, some babies are born with terminal hair instead of vellus hair. However, these hairs typically shed after birth when hormones level off.

Vellus hair is also common with male pattern baldness. This type of hair loss occurs when a hormone called DHT damages hair follicles. As a result of this damage, terminal hairs thin and vellus hairs appear.

Vellus hairs are normal, and the number of tiny hairs you develop throughout your life may vary. Although these hairs are common, don’t hesitate to speak with your doctor if you notice an increase. This can indicate a medical problem.