Why Do We Have Body Hair Anyway?

body_hair

As it turns out, body hair has many important uses.

No one ever complains about having too much hair on their head! But in every other part of the body, hair is such a huge bother, particularly for women. Likely every single person who’s walked into a clinic to get laser hair removal has thought, “Why do we even have hair on our arms, legs, etc.? It seems so useless!”

But hair really, really isn’t useless at all, and here’s why:

  • Hair plays a role in sexual attraction. It provides a large amount of surface area off of which pheromones evaporate.
  • It helps you feel the lightest touches. It’s tough to feel a mosquito’s soft landing, but your hair will tell you it’s there.
eyebrows_body_hair

Eyebrow shape and style changes with time, but eyebrows have more function than just frames for the eyes.

  • Eyebrow hair prevents sweat from getting into eyes.
  • Armpit and groin hair decreases friction, and because it provides extra surface area off of which sweat evaporates, it helps the body cool down.
  • Eyelashes, nose and ear hair prevents tiny particles from entering and causes irritation to these organs.
  • A hair follicle – and this is my favorite part! –  acts as a reservoir for a number of vital cells present in the skin:
      • After an injury, hair follicles provide skin and sebaceous gland cells necessary for the initial steps of wound healing.
vitiligo_repigmentation

Perifollicular re-pigmentation seen in vitiligo that’s being treated

      • Melanocyte reservoirs are present in hair follicles to give pigment to hair and skin. Patients with vitiligo experience re-pigmentation of their skin around the orifices of hair follicles first, then that color spreads to the rest of the depigmented skin.
      • Langerhans cell and leucocyte reservoir are important for warding off microorganisms.
      • Merkel cells, also present in the hair follicle, contribute to the sense of touch and object discrimination.

It is believed that if hair follicles are completely destroyed, wound repair and skin pigmentation can be compromised. However, this should not alarm anyone seeking laser hair removal. Even the best laser hair removal device today cannot completely and permanently eliminate hair. Yes, hair numbers and speed of growth are hindered drastically, but hair follicles are pretty tough to get rid of. So reservoirs remain and take good care of the skin when it is wounded and in need of replenishment.

arrector_pili_muscles

One of hairs main purposes in our evolutionary history was to stand on end.

Bonus Info: to this day, it fascinates me to think of every tiny hair having its very own tiny muscle. In earlier evolutionary phases, arrector pili muscles would pull hairs up, trapping air, which acted as an insulating layer to prevent heat loss and maintain body temperature. Hair standing on end also gives the illusion of being bigger and more intimidating to a possible attacker.

Of course, both these traits are more pronounced in animals than the modern human. Today, we simply get goose bumps when our arrector pili muscles make our hairs stand on it, but it doesn’t really add any significant amount of warmth, nor is it all that intimidating!

Thank you for reading!

 

Sources

Melanocyte stem cells: a melanocyte reservoir in hair follicles for hair and skin pigmentation – Emi K. Nishimura – Pigment Cell & Melanoma Research – Volume 24, Issue 3, pages 401–410, June 2011.

Hair follicle bulge: A fascinating reservoir of epithelial stem cells – Manabu Ohyama – Journal of Dermatological Science – Volume 46, Issue 2, May 2007, Pages 81-89.

Epidermal stem cells arise from the hair follicle after wounding – Vered Levy, Catherine Lindon, Ying Zheng, Brian D. Harfe, Bruce A. Morgan – The FASEB Journal. 2007; 21:1358-1366.

K. Sellheyer. Mechanisms of Laser Hair Removal: Could Persistent Photoepilation Induce Vitiligo or Defects in Wound Repair? Dermatologic Surgery 2007; 33 (9) 1055-65.

 

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