This is an illustration demonstrating the Wolfsdorf Staging for axillary hair development in children.[1][2]
Underarm or axillary hair goes through four stages of development, as staged by theWolfsdorf Axillary Hair Scale,[2] driven by weakandrogens produced by theadrenal in males and females duringadrenarche, andtestosterone from thetesticle in males duringpuberty.[3]
The Wolfsdorf Axillary Hair Staging system provides a standardized method for assessingpubertal progression andandrogenic activity inpediatric populations. Similar toTanner Staging forpubic 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 wicksweat or other moisture away from the skin, aiding ventilation. Colonization by odor-producingbacteria is thereby transferred away from the skin (seeskin flora).[4]
Male axilla
Female axilla
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.[5][better source needed]
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.[6]
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 recentshaving.[8]
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."[9] However, later studies have disputed this and found no significant increase in breast cancer among users.[10]
^Hofer MK, Collins HK, Whillans AV, Chen FS (January 2018). "Olfactory cues from romantic partners and strangers influence women's responses to stress".Journal of Personality and Social Psychology.114 (1):1–9.doi:10.1037/pspa0000110.PMID29293018.S2CID40410769.
^McGrath KG (December 2003). "An earlier age of breast cancer diagnosis related to more frequent use of antiperspirants/deodorants and underarm shaving".European Journal of Cancer Prevention.12 (6):479–485.doi:10.1097/00008469-200312000-00006.PMID14639125.S2CID24938503.
Media related toUnderarm hair at Wikimedia Commons