Body hair

Body hair, or androgenic hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair, which are much finer and lighter in color. The growth of androgenic hair is related to the level of androgens (male hormones) in the individual. Due to a normally higher level of androgen, men tend to have more androgenic hair than women.

From childhood onward, regardless of sex, vellus hair covers almost the entire area of the human body. Exceptions include the lips; the backs of the ears; the palms of hands; the soles of the feet; certain external genital areas; the navel; and scar tissue. The density of hair – i.e. the number of hair follicles per unit area of skin – varies from person to person. In many cases, areas on the human body that contain vellus hair will begin to produce darker and thicker body hair, such as the first growth of beard hair on a male adolescent's previously smooth chin.

Androgenic hair follows the same growth pattern as the hair that grows on the scalp, but with a shorter anagen phase and longer telogen phase. While the anagen phase for the hair on one's head lasts for years, the androgenic hair growing phase lasts a few months. The telogen phase for body hair lasts close to a year. This shortened growing period and extended dormant period explains why the hair on the head tends to be much longer than other hair found on the body. Differences in length seen in comparing the hair on the back of the hand and pubic hair, for example, can be explained by varied growth cycles in those two regions. The same goes for differences in body hair length seen in different people, especially when comparing men and women.

Hair

Hair is a protein filament that grows from follicles found in the dermis, or skin. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fine vellus hair. Most common interest in hair is focused on hair growth, hair types and hair care, but hair is also an important biomaterial primarily composed of protein, notably keratin. Attitudes towards hair, such as hairstyles and hair removal, vary widely across different cultures and historical periods, but it is often used to indicate a person's personal beliefs or social position, such as their age, gender, or religion.

Overview

The word "hair" usually refers to two distinct structures: