Vellus hair

Vellus hair
Vellus hair
Comparison of the vellus hair (left) to the terminal hair (right) in humans.
Anatomical terminology []

Vellus hair is short, thin, slight-colored, and barely noticeable thin hair that develops on most of a person's body during childhood. Exceptions include the lips, the back of the ear, the palm of the hand, the sole of the foot, some external genital areas, the navel, the forehead and scar tissue. The density of hair – the number of hair follicles per area of skin – varies from person to person. Each strand of vellus hair is usually less than 2 mm (1/13 inch) long and the follicle is not connected to a sebaceous gland.

Vellus hair is most easily observed on children and adult women, as it generally has less terminal hair to obscure it. Vellus hair is not lanugo hair. Lanugo hair is a much thicker type of hair that normally grows only on fetuses.

Vellus hair is differentiated from the more visible terminal or androgenic hair, which develops only during and after puberty, usually to a greater extent on men than it does on women.

The Latin language uses the word vellus to designate "a fleece" or "wool". In slang usage, vellus hair is sometimes referred to as "peach fuzz" due to its resemblance to the downy epidermic growths on the peach fruit.

Vellus hair replaces lanugo hair on a human fetus at 36 to 40 weeks of gestation. The growth cycle of vellus hair is different from the growth cycle of terminal hair. At puberty, androgen hormones cause much of the vellus hair to turn into terminal hair and stimulates the growth of new hair in the armpit and the pubic area. In men, this change in vellus hair occurs on the face and the body.