Underarm hair

File:Staging for Axillary Hair Development.jpg

Underarm or axillary hair goes through four stages of development, as staged by the Wolfsdorf Axillary Hair Scale, driven by weak androgens produced by the adrenal in males and females during adrenarche, and testosterone from the testicle in males during puberty.{{cite journal | vauthors = Auchus RJ, Rainey WE | title = Adrenarche - physiology, biochemistry and human disease | journal = Clinical Endocrinology | volume = 60 | issue = 3 | pages = 288–296 | date = March 2004 | pmid = 15008992 | doi = 10.1046/j.1365-2265.2003.01858.x | doi-access = free }}

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).{{cite book | vauthors = Paye M, Maibach HI, Barel AO |title=Handbook of cosmetic science and technology |edition=3 |year=2009 |publisher=Informa Health Care |isbn=978-1-4200-6963-1 |page=703}}

File:Armpit by David Shankbone.jpg | Male axilla

File:Womans armpit.JPG | Female axilla

File:Armpit of a Teenager,in developement,Mar 2013.jpg | Axillia of a pubescent male, note the short, stray hairs characteristic of this stage (Wolfsdorf 2)

Armpit hair prevents skin-to-skin contact during activities that involve arm motion, such as running and walking. The same applies to pubic hair.{{Cite journal |date=2007 |title=MRSA superbug? Part 1 |url=http://dx.doi.org/10.1037/e721542007-001 |access-date=12 July 2022 |website=PsycEXTRA Dataset|doi=10.1037/e721542007-001 }}{{bsn|date=June 2022}}

The armpits release odor-containing pheromones, a naturally produced chemical that plays 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.{{cite journal | vauthors = Hofer MK, Collins HK, Whillans AV, Chen FS | title = Olfactory cues from romantic partners and strangers influence women's responses to stress | journal = Journal of Personality and Social Psychology | volume = 114 | issue = 1 | pages = 1–9 | date = January 2018 | pmid = 29293018 | doi = 10.1037/pspa0000110 | s2cid = 40410769 }}

А 2012 study on the impact of hair removal on odor found that shaved armpits were rated the same as unshaved armpits.{{Cite journal | vauthors = Kohoutová D, Rubešová A, Havlíček J |date= April 2012 |title=Shaving of axillary hair has only a transient effect on perceived body odor pleasantness |journal=Behavioral Ecology and Sociobiology |language=en |volume=66 |issue=4 |pages=569–581 |doi=10.1007/s00265-011-1305-0 |bibcode= 2012BEcoS..66..569K |s2cid= 16607684 |issn=0340-5443}}

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.{{cite journal | vauthors = Klotz K, Weistenhöfer W, Neff F, Hartwig A, van Thriel C, Drexler H | title = The Health Effects of Aluminum Exposure | journal = Deutsches Ärzteblatt International | volume = 114 | issue = 39 | pages = 653–659 | date = September 2017 | pmid = 29034866 | pmc = 5651828 | doi = 10.3238/arztebl.2017.0653 }}

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."{{cite journal | vauthors = McGrath KG | title = An earlier age of breast cancer diagnosis related to more frequent use of antiperspirants/deodorants and underarm shaving | journal = European Journal of Cancer Prevention | volume = 12 | issue = 6 | pages = 479–485 | date = December 2003 | pmid = 14639125 | doi = 10.1097/00008469-200312000-00006 | s2cid = 24938503 }} However, this was later proven to be false.{{Cite journal |last1=Mousavi |first1=Maryam |last2=Vaghar |first2=Mohammad I |date=January 2021 |title=The relationship between use of aluminum-containing anti-perspirant and hair color with breast cancer |journal=Journal of Family Medicine and Primary Care |volume=10 |issue=1 |pages=182–186 |doi=10.4103/jfmpc.jfmpc_1219_19 |doi-access=free |issn=2249-4863 |pmc=8132781 |pmid=34017723}}

• Adrenal gland
• Adrenarche
• Ferriman–Gallwey score
• Hirsutism
• History of removal of leg and underarm hair in the United States
• Puberty
• Tanner staging

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• {{Commons category-inline|Underarm hair}}

{{Human hair}}

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Category:Axillas

Category:Human hair