<P> Abdominal hair is the hair that grows on the abdomen of humans and non-human mammals, in the region between the pubic area and the thorax (chest). The growth of abdominal hair follows the same pattern on nearly all mammals, vertically from the pubic area upwards and from the thorax downwards to the navel . The abdominal hair of non-human mammals is part of the pelage, (hair or fur). </P> <P> Before puberty, the abdominal region of both males and females is covered with very fine vellus hair . In response to rising levels of androgens (mainly testosterone) during and after puberty, the skin of the abdomen begins to produce coarser, longer and more pigmented hair (terminal hair). This process primarily affects men . Initially hair grows in a vertical line from the pubic area up to the navel and from the thorax down to the navel . Slang terms for this line of hair include "goodie trail", "snail trail", "tiger line", or "treasure trail". Although the development of abdominal hair normally begins during puberty, it may also start later, between the ages of 20 and 30 . With some men, the abdominal hair will stay within a clearly defined vertical line, but in others, terminal hair will appear laterally as well as vertically, particularly in the area around the navel . This lateral spreading can continue into middle age . </P> <P> Some women may develop a small line of hair from the pubic area up to the navel . Excessive abdominal hair on women, following the male pattern, is a type of hirsutism . </P>

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