Underarm hair
Template:Short description Template:Use dmy dates Template:Infobox anatomy Underarm hair, also known as axillary hair or armpit hair, is human hair in the underarm area (axilla).
In some cultures, underarm hair removal through shaving or other means is common, particularly among women.
Development
Underarm or axillary hair goes through four stages of development, as staged by the Wolfsdorf Axillary Hair Scale,<ref name=":0" /> driven by weak androgens produced by the adrenal in males and females during adrenarche, and testosterone from the testicle in males during puberty.<ref>Template:Cite journal</ref>
The Wolfsdorf Axillary Hair Staging system provides a standardized method for assessing pubertal progression and androgenic activity in pediatric populations. Similar to Tanner Staging for pubic hair, it classifies axillary hair growth into four stages:
- Wolfsdorf Stage 1 – No axillary hair
- Wolfsdorf Stage 2 – Sparse, soft hair
- Wolfsdorf Stage 3 – Coarser hair with increased volume
- Wolfsdorf Stage 4 – Full adult-like axillary hair
The importance of human underarm hair is unclear. It may naturally wick sweat or other moisture away from the skin, aiding ventilation. Colonization by odor-producing bacteria is thereby transferred away from the skin (see skin flora).<ref>Template:Cite book</ref>
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Male axilla
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Female axilla
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Axillia of a pubescent male, note the short, stray hairs characteristic of this stage (Wolfsdorf 2)
Function
Reducing friction
Armpit hair prevents skin-to-skin contact during activities that involve arm motion, such as running and walking. The same applies to pubic hair.<ref>Template:Cite journal</ref>Template:Better source needed
Spreading pheromones
The armpits release odor-containing pheromones, naturally produced chemicals that play an important role in sexual attraction. Armpit hair traps odor, making the pheromones even stronger. A study in 2018 including 96 heterosexual couples found that there were stress-relieving benefits to smelling a romantic partner's natural scent.<ref>Template:Cite journal</ref>
Impact of hair removal
Effect on odor
А 2012 study on the impact of hair removal on odor found that shaved armpits were rated the same as unshaved armpits.<ref>Template:Cite journal</ref>
Chemical absorption
A 2017 study on chemical absorption from deodorants as a result of hair removal showed an increase in chemical absorption from .01% to .06% where skin has been damaged by recent shaving.<ref>Template:Cite journal</ref>
A 2003 study on aluminum antiperspirant usage and the age of breast cancer onset tentatively concluded that "underarm shaving with antiperspirant/deodorant use may play a role in breast cancer."<ref>Template:Cite journal</ref> However, later studies have disputed this and found no significant increase in breast cancer among users.<ref>Template:Cite journal</ref>
See also
- Adrenal gland
- Adrenarche
- Ferriman–Gallwey score
- Hirsutism
- History of removal of leg and underarm hair in the United States
- Puberty
- Tanner staging