Body hair may seem like an unnecessary inconvenience, especially for postpubertal girls and women, but the growth of hair on the body occurs from birth. The distribution of hair throughout the body is determined by genetic factors and hormones. The largest concentration of hair is on the head (scalp hair) while the hands and feet have the least amount of hair follicles. There are different types of hair that occur on different parts of the body. The type of hair also changes at different times in life, under the influence of various factors, particularly hormones.
Types of Body Hair
Body hair seems like a male characteristic. But it also occurs in females. Due to the difference in hormones between the male and female bodies, body hair is thicker and more dense in males. However, body hair growth is a secondary sexual characteristic that is common to both genders. It tends to increase and become more prominent from the time of puberty. It is most concentrated in the armpits and pubic region of women, apart from the scalp.
Hair on different parts of the body is not always of the same type. Finer hair known as vellus hair is distributed through most of the body both in women and men. It replaces the very fine hair known as lanugo which is present from birth. The type of hair changes again at puberty. In females, the hair that grows on the pubic region and armpits from the time of puberty is known as terminal hair. In men, this type of hair also occurs on the chest and face (beard).
Although women also have hair on their face, it is usually of the fine vellus type. Thicker terminal hair can occur on the upper lip and chin of some women but this is usually indicative of hormonal disturbances.
How does body hair grow?
Hair grows from the follicles embedded in the skin. It is made up of the same protein as the outer layer of skin – keratin. The color of hair is determined by genetics and the concentration of the skin pigment, melanin, deposited at the root. The growth of terminal hair in the armpits and pubic region is determined by hormones, particularly androgens (male sex hormones). These hormones do not only occur in males. It is also present in females but to a much lesser extent than in the male body.
Hair growth is not continuous. It goes through different stages. Anagen is the active growth phase followed by the catagen phase. During the short catagen phase, there are changes that occur at the part of the shaft that is in contact with the follicle. It is then followed by telogen which can be of variable length. During telogen, hair growth stops and hair may then fall off. The entire cycle occurs over a long period of time so some hair follicles are in anagen, while a few are in catagen and others are in telogen. This means that there is no overgrowth of hair nor is there a total loss of hair under normal circumstances.