The Tanner scale looks at the development of pubic hair. Before the onset of puberty, the genital area of both boys and girls has very fine vellus hair, referred to as Tanner stage 1 hair.[1] As puberty begins, the body produces rising levels of the sex hormones, and in response the skin of the genital area begins to produce thicker and rougher, often curlier, hair with a faster growth rate.[2] The onset of pubic hair development is termed pubarche. The change for each hair follicle is relatively abrupt, but the extent of skin which grows androgenic hair gradually increases over several years.
In males, the first pubic hair appears as a few sparse hairs that are usually thin on the scrotum or at the upper base of the penis (stage 2). Within a year, hairs around the base of the penis are numerous (stage 3). Within 3 to 4 years, hair fills the pubic area (stage 4) and becomes much thicker and darker, and by 5 years extends to the near thighs and upwards on the abdomen toward the umbilicus (stage 5).[3]
Other areas of the skin are similarly, though slightly less, sensitive to androgens and androgenic hair typically appears somewhat later. In rough sequence of sensitivity to androgens and appearance of androgenic hair, are the armpits (axillae), perianal area, upper lip, preauricular areas (sideburns), periareolar areas (nipples), middle of the chest, neck under the chin, remainder of chest and beard area, limbs and shoulders, back, and buttocks.
Although generally considered part of the process of puberty, pubarche is distinct and independent of the process of maturation of the gonads that leads to sexual maturation and fertility. Pubic hair can develop from adrenal androgens alone, and can develop even when the ovaries or testes are defective and nonfunctional. See puberty for details.
There is little if any difference in the capacity of male and female bodies to grow hair in response to androgens. The obvious sex-dimorphic difference in hair distribution in men and women is primarily a result of differences in the levels of androgen reached as maturity occurs.
Pubic hair and axillary (armpit) hair can vary in color considerably from the hair of the scalp. In most people it is darker, although it can also be lighter. In most cases it is most similar in color to the eyebrows of the individual.[4]
Natural female pubic hair varies considerably around the world, ranging from short to long, from sparse to dense, and from straight and soft to wiry and curly. In color, pubic hair does not always match head hair. Many dark-haired women have lighter pubic hair often with a red tinge. Most women have wavy and curly pubic hair, even when their head hair is straight. In the Far East, however, straight black head hair is matched by pubic hair that has been described as 'black, short, straight and not thick but rather sparse...'[4][5] Hair texture varies from tightly curled to entirely straight. Such variations also appear in men.
Pubic hair patterns can vary by race and ethnicity.[5] Patterns of pubic hair, known as the escutcheon, vary between sexes. On most women, the pubic patch is triangular and lies over the vulva and mons pubis. On many men, the pubic patch tapers upwards to a line of hair pointing towards the navel (see abdominal hair), roughly a more upward-pointing triangle.[4] As with axillary (armpit) hair, pubic hair is associated with a concentration of sebaceous glands in the area.
