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Body hair or androgenic hair is terminal hair that develops on the human body during and after puberty. It is different from head hair and also from less visible vellus hair, which is much finer and lighter in color. Growth of androgenic hair is related to the level of (male ) and the density of androgen receptors in the dermal papillae. Both must reach a threshold for the proliferation of hair follicle cells.
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, palms of hands, soles of the feet, certain external genital areas, the navel, and scar tissue. Density of hair – i.e. the number of 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 during puberty, such as the first growth of Beard on a male and female adolescent's previously smooth chin; although it may appear thinner on the female.
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 growth phase for body hair lasts a few months. The telogen phase for hair lasts for varying lengths of time, depending on where the hair is, from a few weeks up to nearly 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 regions. The same goes for differences in body hair length seen in different people, especially when comparing men and women.
Terminal hair growth on is a secondary sexual characteristic in boys and appears in the last stages of puberty. Vellus arm hair is usually concentrated on the elbow end of the forearm and often ends on the lower part of the upper arm. This type of intense arm vellus hair growth sometimes occurs in girls and children of both sexes until puberty. Even though this causes the arms to appear hairy, it is not caused solely by testosterone. The hair is softer and different from terminal arm hair, in texture.
The longest arm hair ever recorded was done so in California by David Reed in 2017. In 2024, Macie Davis-Southerland measured one hair at 7.24 inches long.
The genital area of males and females are first inhabited by shorter, lighter vellus hairs that are next to invisible and only begin to develop into darker, thicker pubic hair at puberty. At this time, the pituitary gland secretes gonadotropin hormones which trigger the production of testosterone in the testicles and ovaries, promoting pubic hair growth. The average ages pubic hair begins to grow in males and females are 12 and 11, respectively. However, in some females, pubic hair has been known to start growing as early as age 8.
Just as individual people differ in scalp hair color, they can also differ in pubic hair color. Differences in thickness, growth rate, and length are also evident.
Today in much of the world, it is common for women to regularly Shaving their underarm hair. The prevalence of this practice varies widely, though. The practice became popular for cosmetic reasons around 1915 in the United States and United Kingdom, when one or more magazines showed a woman in a dress with shaved underarms. Regular shaving became feasible with the introduction of the safety razor at the beginning of the 20th century. While underarm shaving was quickly adopted in some English language speaking countries, especially in the US and Canada, it did not become widespread in Europe until well after World War II. Since then the practice has spread worldwide; some men also choose to shave their armpits.
It is common for many women to develop a few facial hairs under or around the chin, along the sides of the face (in the area of sideburns), or on the upper lip. These may appear at any age after puberty but are often seen in women after menopause due to decreased levels of estrogen. A darkening of the vellus hair of the upper lip in women is not considered true facial hair, though it is often referred to as a "moustache"; the appearance of these dark vellus hairs may be lessened by bleaching. A relatively small number of women are able to grow enough facial hair to have a distinct beard. In some cases, female beard growth is the result of a hormonal imbalance (usually androgen excess), or a rare genetic disorder known as hypertrichosis. Sometimes it is caused by use of . Cultural pressure leads most women to remove facial hair, as it may be viewed as a social stigma.
Rising levels of androgens during puberty cause vellus hair to transform into terminal hair over many areas of the body. The sequence of appearance of terminal hair reflects the level of androgen sensitivity, with pubic hair being the first to appear due to the area's special sensitivity to androgen. The appearance of pubic hair in both sexes is usually seen as an indication of the start of a person's puberty. There is a sexual differentiation in the amount and distribution of androgenic hair, with men tending to have more terminal hair in more areas. This includes facial hair, chest hair, abdominal hair, leg hair, arm hair, and foot hair. (See Table 1 for development of male body hair during puberty.) Women retain more of the less visible vellus hair, although leg, arm, and foot hair can be noticeable on women. It is not unusual for women to have a few terminal hairs around their nipples as well. In the later decades of life, especially after the fifth decade, there begins a noticeable reduction in body hair especially in the legs. The reason for this is not known but it could be due to poorer circulation, lower free circulating hormone amounts or other reasons.
The thermodynamic properties of hair are based on the properties of the keratin strands and amino acids that combine into a 'coiled' structure. This structure lends to many of the properties of hair, such as its ability to stretch and return to its original length. This coiled structure does not predispose curly or frizzy hair, both of which are defined by oval or triangular hair follicle cross-sections.
Markus J. Rantala of the Department of Biological and Environmental Science, University of Jyväskylä, Finland, said humans evolved by "natural selection" to be hairless when the trade off of "having fewer parasites" became more important than having a "warming, furry coat".
P. E. Wheeler of the Department of Biology at Liverpool Polytechnic said Quadrupedalism savanna of similar volume to humans have body hair to keep warm while only larger quadrupedal savanna mammals lack body hair, because their body volume itself is enough to keep them warm. Therefore Wheeler said that humans, who should have body hair based on predictions of body volume alone for savanna mammals, evolved no body hair after evolving bipedalism, which he said reduced the amount of body area exposed to the sun by 40%, reducing the solar warming effect on the human body.
Loss of fur occurred at least two million years ago, but possibly as early as 3.3 million years ago judging from the divergence of Head louse and Crab louse, and aided persistence hunting (the ability to catch prey in very long distance chases) in the warm savannas where hominins first evolved. The two main advantages are felt to be bipedal locomotion and greater thermal load dissipation capacity due to better sweating and less hair.Kittler R, Kayser M, Stoneking M: "Molecular evolution of Pediculus humanus and the origin of clothing". Curr Biol. 2003, 13: 1414–1417. . Erratum: Curr Biol 2004, 14:2309.
Anthropologist Joseph Deniker said in 1901 that the very hirsute peoples are the Ainu people, Uyghurs, Iranian peoples, Australian aborigines (Arnhem Land being less hairy), Toda people, Dravidian people and Melanesians, while the most glabrous peoples are the Indigenous Americans, San people, and , who include Chinese people, Koreans, , and Malay people. Deniker said that hirsute peoples tend to have thicker beards, eyelashes, and eyebrows but fewer hairs on their scalp.
C.H. Danforth and Mildred Trotter of the Department of Anatomy at Washington University in St. Louis conducted a study using American army soldiers of European origin in 1922 where they concluded that dark-haired white people men are generally more hairy than fair-haired white men.
H. Harris, publishing in the British Journal of Dermatology in 1947, wrote Native Americans have the least body hair, Chinese people people and black people have little body hair, white people have more body hair than black people and Ainu have the most body hair.
Anthropologist Arnold Henry Savage Landor described the Ainu as having hairy bodies. (2025). 9781108049412 ISBN 9781108049412
Stewart W. Hindley and Albert Damon of the Department of Anthropology at Stanford University studied, in 1973, the frequency of hair on the middle finger joint (mid-phalanges hair) of , as a part of a series of anthropometric studies of these populations. They summarize other studies on prevalence of this trait as reporting, in general, that are more likely to have hair on the middle finger joint than , Australoids and , and collect the following frequencies from previously published literature: Andamanese 0%, Inuit 1%, African American 16% or 28%, Ethiopian people 25.6%, Mexican people of the Yucatan 20.9%, Penobscot people and Shinnecock 22.7%, Gurkha 33.6%, Japanese people 44.6%, various 40–50%, Egyptian people 52.3%, Near Eastern peoples 62–71%, various Europeans 60–80%. However, they never completed an Androgenic hair map.
According to anthropologist and professor Ashley Montagu in 1989, many East Asian people and African populations such as the San people are less hairy than Europeans and West Asian peoples. Montagu said that the hairless feature is a Neoteny trait.Montagu, Ashley. Growing Young. Published by Greenwood Publishing Group, 1989
Eike-Meinrad Winkler and Kerrin Christiansen of the Institut für Humanbiologie studied, in 1993, the Kavango people people and !Kung people from Namibia of body hair and hormone levels to investigate the reason some Africans did not have bodies as hairy as Europeans. Winkler and Christiansen concluded the difference in hairiness between some Africans and Europeans had to do with differences in androgen or estradiol production, in androgen metabolism, and in sex hormone action in the target cells.
Valerie Anne Randall of the Department of Biomedical Sciences, University of Bradford, said in 1994 beard growth in Caucasian men increases until the mid-thirties due to a delay caused by growth cycles changing from vellus hair to terminal hair. Randall said white men and women are hairier than Japanese men and women even with the same total plasma androgen levels. Randall says that the reason for some people being hairy and some people not being hairy is unclear, but that it probably is related to differing sensitivity of to 5α-reductase.
Rodney P. R. Dawber of the Oxford Hair Foundation said in 1997 that East Asian males have little or no facial or body hair and Dawber also said that Mediterranean males are covered with an exuberant pelage.Dawber R.P.R. (1997). Diseases of the Head and Scalp (3rd ed.). Virginia: Blackwell Science Ltd.
Milkica Nešić and her colleagues from the Department of Physiology at the University of Niš, Serbia, cited prior studies in a 2010 publication indicating that the frequency of hair on the middle finger joint (mid-phalanges hair) in Europeans is significantly higher than in African populations, where the lowest values were found, and "completely absent" in Northern Native American (Inuit) populations. Their own study found that the latter was part of a wider trend of "Mongoloid" peoples having less hair overall.Nešić, M. et al. (2010). "Middle phalangeal hair distribution in Serbian high school students". Arch. Biol. Sci., Belgrade, 62 (3), 841–850, .
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