Overview

Development

Under the influence of weak androgens generated by the adrenal in both males and females throughout sexual maturation (adrenarche), underarm or axillary hair passes through four phases of growth. Additionally from testosterone produced by the male testicles during late puberty.

Stages

According to the method created by pediatric endocrinologist Joseph Wolfsdorf, underarm hair can be categorized in the following stages:

• Wolfsdorf Stage 1- no axillary hair
• Wolfsdorf Stage 2- scant axillary hair (usually coinciding with onset of adrenarche)
• Wolfsdorf Stage 3- coarse axillary hair, less than full-adult
• Wolfsdorf Stage 4- full adult axillary hair

This method is similar to the Tanner Staging for pubic hair.

Function

The evolutionary relevance of human underarm hair is still questioned. In order to assist with ventilation, it could naturally wick sweat or other moisture away from the skin. As a result, colonization by odor-producing bacteria is moved away from the skin.

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.

Spreading pheromones

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.

Cultural attitudes

Shaving

In the majority of the Western world nowadays, women frequently shave their underarm hair. men of older generations rarely trim or shave their underarms, while younger men are increasingly doing so.

Historical factors

The practice started in the United States and the United Kingdom around 1915, when magazines featured women in dresses with shaved armpits. With the invention of the safety razor at the start of the 20th century, shaving on a regular basis became possible. While underarm shaving became quite popular quite quickly in several English-speaking nations, including Canada, it did not catch on in Europe until well after World War II.

In Art

Usually, underarm hair is eliminated while creating works of art; demonstrating it is a sign of modernism. In contrast, pubic hair gradually gained in popularity, appearing less frequently in Middle Ages art and more frequently in Renaissance art and contemporary art.

Usage

On Pixiv, This tag is frequently used to encompass images were male and female armpit hair is present.