The History of Hair Removal
Hair removal remained important as a sign of civilization and social status. Roman soldiers – who shaved their heads to prevent hair-pulling in battle – coined the term ‘barbarian’ in reference to the un-barbered enemy.
The Biology of Human Hair
the medulla, the cortex, and the cuticle, as shown in Fig. 2.
The medulla makes up the center of the hair, the cortex surrounds the medulla and is made out of roughly straight keratin structures, and the cuticle is the outside of the hair, made up of flat cells laid out like roof shingles . The hair itself is part of a biological system that includes the follicle, where the hair grows, the sebaceous gland, which when infected produces pimples, and the arrector pili muscle, which causes goose bumps.
The Physics behind Laser Technology
What is a Laser?
, a material through which specific wavelengths of light can be amplified. The other essential parts of the laser include a mechanism to apply energy to the Gain Medium, and a reflector or other way to provide optical feedback. Energy is applied to the Gain Medium, the electrons in the medium are excited to a higher orbital, and then they fall to a lower orbital, emitting light as a byproduct. The purity of the Gain Medium affects the purity of the spectrum emitted. A high quality laser should emit a very narrow spectrum . This narrow spectrum is characterized graphically in Fig. 3, which shows that the spectrum of a helium-neon laser is confined to a small range of frequencies centered around 632 nanometers.
How Laser Hair Removal Works
Laser hair removal works by targeting areas with specific chromophores – in this case, the melanin found in the hair (See previous section for a description of chromophores). The laser emits a wavelength of light that should be primarily absorbed by the hair and primarily reflected by skin, causing the hair follicle to heat up faster than the surrounding skin. This causes inflammation, which will kill the follicle that produces the hair. However, one should not expect to go in for a treatment and come out hairless – it can take up to three weeks for the affected follicles to shed the treated hair.
No single laser works on the complete range of skin and hair types (skin color is less relevant than melanin content), since the laser hair removal system works based upon a difference between skin and hair color in order for the hair to absorb the light without burning the skin. Melanin under the skin – even if inactivated, will absorb rather than reflect light at the same rate as melanin of the same type in the hair. If the skin and hair absorb the light at the same rate, the laser will not be able to “target” the hair. For this reason, for many years laser hair removal was only possible for people with light skin and dark hair. However, new lasers have been invented that work for different skin and hair combinations. For example, the alexandrite laser – which has a relatively short wavelength (775 nanometers) – is effective on patients with lighter skin, although it is dangerous for patients with dark skin, while the neodymium-doped yttrium aluminum garnet laser – developed to have a longer wavelength (1064 nanometers) – works well on darker-skinned patients .
Dangers of Laser Hair Removal
Physics, Culture and Laser Hair Removal
-  Test. (2012, Sept. 5). Laser Hair Removal Statistics. The Hair Removal Journal. [Online]. Available: http://www.statisticbrain.com/laser-hair-removal-statistics/
-  M. Lagi. (2012, May). Impact of Ethanol Conversion and Speculation on Mexico Corn Imports. New England Complex Systems Institute. [Online]. Available: http://necsi.edu/research/social/foodprices/mexico/
-  Test. (2012, Sept 12). Egyptian Beauty Secrets: Article Two. Tour Egypt. [Online] Available: http://www.touregypt.net/egypt-info/magazine-mag07012000-mag4.htm
-  N. Torres. (2012). See Hairy Celebrity Slips: Armpits, Legs, Guess Who? About.com. [Online]. Available: http://hairremoval.about.com/od/waxing/ss/celebrity-slips_2.htm
-  R.B. Adams. (1978). King C. Gillette: The Man and His Wonderful Shaving Device. [Online] Available: http://web.mit.edu/invent/iow/gillette.html
-  M. Feughelman. “The Morphology of Wools and Hairs” in Mechanical Properties and Structure of Alpha-Keratin Fibres: Wool, Human Hair and Related Fibres. Sydney, Australia: University of New South Wales Press, 1996.
-  Test. (2012 Sept. 16). Chromophore. Wikipedia. [Online]. Available: http://en.wikipedia.org/wiki/Chromophore
-  D. P. Ketumahkha. (2004 May 24). The Bohr Atom. [Online] Available: http://venables.asu.edu/quant/Dinesh/Bohratom2.html
-  American Institute of Physics. (2012). Bright Idea: The First Lasers. [Online] Available: http://www.aip.org/history/exhibits/laser/sections/whoinvented.html
-  Lawrence Livermore National Laboratory (2012 Sept. 13). Education: How Lasers Work, NIF & Photon Science. [Online] Available: https://lasers.llnl.gov/education/how_lasers_work.php
-  Mayo Clinic (2012). Laser Hair Removal. [Online]. Available: http://www.mayoclinic.com/health/laser-hair-removal/MY00134/
-  Test. (2012 Sept. 16). Laser Hair Removal. Wikipedia. [Online]. Available: http://en.wikipedia.org/wiki/Laser_hair_removal
-  A. Thompson. (2011). Understanding Pulsed Light Hair Removal. [Online]. Available: http://www.ajthompson.com.au/human-sciences/understanding-pulsed-light-hair-removal.htm
-  A. James. (2001 August 21). Hair Removal methods: Laser History and Current Issues. [Online]. Available: http://www.quackwatch.com/01QuackeryRelatedTopics/Hair/laserhistory.html
-  Test. (2012 Sept.) Education: Photochemistry. Zerona. [Online]. Available: http://www.myzerona.com/education-photochemistry-0