Laser Use in Hair Removal

Abstract
Hair is a universal feature of the human body, with a complex structure. Hair can be removed in multiple ways, and there is a long tradition of doing so. Among the many methods, using lasers for this purpose is a newer technological innovation. The laser focuses on the pigment in hair, pulsing and firing a beam of light, which is absorbed by the hair. This results in the vaporization of the bulb, causing the hair to fall out. Multiple risks are associated with this procedure, but it is overall popular and effective when performed correctly.
I. Introduction
Hair, a basic biological feature of the human body, grows everywhere on the skin’s surface, except for the soles of the feet and the palms of the hands. For some, this is not a problem. For others, hair is a nuisance to be removed. Today, permanent hair removal is possible with the use of lasers. Their high-powered beams can eliminate unwanted hair follicles with ease and a short recovery time. Several types of lasers can remove hair. These different types interact with follicles in various ways, depending upon hair characteristics. Lasers also affect the tissue surrounding the targeted hair in various ways, representing the risks and benefits of this delicate procedure.

II. What is Hair?
Human hair comes in several forms, each of which can be found throughout the body. Lanugo is the fine hair that covers almost the entire body of fetuses, terminal hair is fully developed hair, which is coarse and thick, and vellus hair is the softer, less developed “peach fuzz” found nearly everywhere on the human body (Hair 2006). Hair has two separate structures, the follicle within the dermis layer of the skin and the shaft, the visible part above the epidermis, or the top layer of the skin. At the base of the follicle, there is a small projection called the papilla, which is filled with connective tissues and small capillaries responsible for feeding the cells (Montagna & Van Scott 1958: 47). The bulb, the only living part of the hair and the part fed by the mass of capillaries, surrounds the papilla. In the bulb, cells divide every twenty-three to seventy-two hours, faster than any other type of cell in the body (Brannon 2006: 1). The inner root sheath and the outer root sheath surround the follicle. The inner root sheath follows the hair shaft and ends beneath a sebaceous, or oil, gland in the follicle. It is composed of an inner layer one cell thick, a middle layer one to two cells in thickness, also called the cuticle, and an outer layer one cell thick (Montagna & Van Scott 1958: 47). The outer sheath follows the length of the follicle and continues just past the oil gland and the apocrine (scent) gland. It is surrounded by a membrane, and the entire follicle is surrounded by connective tissue.


Figure 1: The biology of a hair follicle (Mayo Clinic: 2003)
Another part of the follicle is a tiny muscle called the arrector pili, which makes the hair shaft stand upright when contracted, responsible for goose bumps (Hair Follicle: 2006). The second main component of hair is the hair shaft, which is composed of the protein keratin and has three layers (Brannon 2006: 1). The innermost layer is the medulla, and may not be present in all shafts. The middle layer is the cortex, and it makes up the majority of the shaft. The outermost layer is the cuticle, which is formed by tightly packed scales in an overlapping pattern (Montagna & Van Scott 1958: 48). Keratin, the protein that creates the shaft, is a hard, dead strand of amino acids that envelops a cell. The color of hair comes from pigment cells distributed throughout the medulla and the cortex, and hair grows .4mm everyday on average (Brannon 2006: 2). Hair follicles and shafts cover nearly all of the human body, something that many individuals wish to change.

III. History of Hair Removal
Hair removal has been a constant occurrence in history, and there are many ways to remove unwanted hair. There are two major categories that hair removal can be divided into, depilation and epilation (Hair Removal 2007). Depilation is the temporary removal of hair above the surface of the skin, essentially eliminating the visible part of the shaft. The most common form of depilation is shaving. Another form of depilation is by the use of chemical depilatories, which work by breaking the protein bonds of the shaft, causing the hair to disintegrate. Shaving has been in existence for multiple thousands of years (Shaving 2007). Before the invention of razors in the Copper Age around 3,000 B.C., seashells were used to remove hairs. Shaving was greatly popularized by Alexander the Great in the 4th century B.C., and was used in many cultures for religious reasons, hygienic benefits, and as punishment in some cultures. Evidence of depilatory crèmes, another form of temporary hair removal, dates back to 4,000 B.C. Pastes containing natural arsenic, quicklime, and starch were used to remove hair (Hair Removal History 2006). Today’s depilatories use calcium thioglycolate to break down the disulfide bonds in keratin, and the Nair Company introduced modern depilatory crèmes in 1940 (Hair Removal in the 20th Century 2006).


Figure 2: Epilation of the eyebrows, or waxing to remove hair. (Amber 2007)
For a permanent result, consumers turn to epilation, the removal of the entire hair, shaft and follicle (Hair Removal 2007). Waxing, tweezing, and lasering are some common forms of epilation. Waxing eliminates the shaft and follicle of the hair, resulting in the longest-lasting temporary results, up to weeks of smooth skin. Wax is heated and applied to the skin, at which point strips of muslin or cotton are applied over it, then pulled off as if a layer of skin was being removed. The original system involved a tray of tallow or wax heated and then applied to the skin, where it was removed without the strips. The wax strip system has been in widespread use since the 1960’s and 1970’s, and modern innovations include cold wax, which is closer to a gel applied to the skin on strips. This method is effective, but changes in temperature can affect results. Tweezing constitutes removing hair individually with tweezers, a lengthy process used most commonly for eyebrows (Hair Removal 2007). Electronic tweezing is a development from the 1960’s, which uses an electric current to remove hair; however, the results are not discernibly different from manual tweezing (Hair Removal in the 20th Century 2006). Lasering is the newest permanent hair removal technique, and requires multiple high-powered elements to produce the desired results.

IV. The Laser
Lasers are cutting-edge technological developments that can be used for a wide variety of things, including hair removal. Laser, an acronym for light amplification by the stimulated emission of radiation, is a light source composed of a beam of photons, which are high-energy fundamental particles that compose all forms of light (Laser 2007). The light that a laser produces is monochromatic, meaning one color and one wavelength, and coherent, meaning all the light waves are in phase with one another (Fisher 2006). Laser light is also collimated, or focused. All the waves travel together to a specific point, without spreading out or diffusing. Albert Einstein began laser development in 1917, when he researched and studied stimulated emission of radiation, the underlying principle in making a laser work (Forward 2006). In 1957, breakthrough research was conducted by Charles Hard Townes, Gordon Gould, and Arthur Leonard Schawlow at Bell Labs in Murray Hill, New Jersey, and the first working laser was made by Theodore H. Maiman in 1960 at Hughes Research Laboratories in Malibu, California. Maiman used a solid-state flash lamp-pumped synthetic ruby crystal to produce red laser light at a wavelength of 694 nanometers. The design of Maiman’s laser was inefficient, and it produced minimal pulses due to design flaws.
Lasers today use stimulated emission, which is the organized emission of photons (Weschler 2007). When two photons in a similarly excited state with the same energy and phase, the one photon can induce emissions that cause the other to vibrate with the same frequency and in the same direction as the inducer. The other key component in a laser is a pair of mirrors, one at each end of the lasing medium. Photons reflect off the mirrors to travel back and forth through the lasing medium. In the process, they stimulate other electrons and can cause the emission of more photons of the same wavelength and phase. A cascade effect occurs, and soon many photons of the same wavelength and phase are traveling through the lasing medium. One of the mirrors is "half-silvered," meaning it reflects some light and lets some light through. The light that makes it through is the monochromatic, coherent, collimated laser light. This laser light interacts with many things, including hair, with varying effects.

V. Use of the Laser to Remove Hair
A. History of Development
Laser hair removal is a recently developed permanent hair removal procedure that targets certain components of the hair in order to eliminate them. Lasers have been used for hair removal since the 1960’s, but widespread use started in 1995, when the first FDA cleared effective laser went on the market (James 2006). Many improvements have been made since the debut of the laser for hair removal, and the cutting-edge technology behind it is continually developing and improving.
B. Common Procedures
Laser hair removal is used most commonly for removing unwanted follicles on the face, arms, and legs, and usually is done in several treatments, depending on the thickness of the hair and residual follicles that grow back following the initial procedure (Skin 2006). Hair removal devices available today include 694 nm ruby lasers, 755 nm alexandrite lasers, 800 nm diode lasers, 1064 nm Nd:YAG lasers, and filtered xenon flashlamps, but any laser that uses a wavelength between approximately 700 and 100nm will be effective, as these are the wavelengths that melanin in the skin absorbs (Dierickx 2002). Pulse duration is dependent upon the width of the hair follicle, and lasers equipped for hair removal can be tuned to different pulse lengths for the best interaction with different size follicles. In most lasers, the pulse length can be set anywhere within a range of 5 to 100 milliseconds.

Figure 3: A patient undergoing laser hair removal. (Laser Hair Removal 2006).
Longer pulses are often considered to be the most effective (Eremia 2000: 2). The pulse must also be matched to the proper amount of energy, or fluence, necessary to cause follicle damage (Dierickx 2002). Hair color and skin color determine the fluence used. Darker skin is treated with a lower energy pulse (between 10 and 20 Joules per square centimeter), while lighter skin can take a pulse up to 40 Joules per square centimeter. Laser removal should be performed at the highest energy level possible, and the coupling of a longer pulse duration with a higher energy pulse produces better, longer-lasting results.
C. Laser-Tissue Interaction
The interface between the laser and the tissue surrounding the targeted hair involves many elements and varies slightly from tissue type to tissue type. Melanin, the pigment responsible for giving hair its color, is the most common target in laser hair removal, but carbon, applied to the skin in the form of a lotion that interacts with the follicles, and hemoglobin, found in the blood, can also be targeted, although it is rare (Laser Hair Removal 2006). The laser looks for one of these three chromophores, then selects the dark matter in the skin and emits a laser pulse as deep as two millimeters into the skin, damaging the hair follicle, consequentially eliminating it. Chromophores can be natural, as in black and brown hair, or introduced, which is necessary in the case of blonde or red hair. Laser procedures may have to be repeated because of the difficulty of targeting lighter colored hair, and those with dark skin and dark hair may have targeting issues as well because of difficulty of discerning between pigments. Hand-held lasers are most commonly used in procedures today (Skin 2006). The laser is pressed against the skin, and when activated the laser light passes through the skin's surface to the hair follicle. The intense heat damages the hair follicle, which inhibits hair growth. A stinging sensation is often felt when the laser is applied to the skin. Pulse lengths and laser wavelengths can affect the results, and it has been shown that longer wavelengths and longer pulses are safer when applied to darker skin tones (Laser Hair Removal 2006).
D. Benefits and Risks
Several precautions are taken during the procedure to lower risk of damage, and there are several side effects that may occur after the procedure. During the procedure, goggles are worn to prevent accidental exposure the eyes to the laser light, which can cause severe and irreversible eye damage (Skin 2006). Oftentimes a topical local anesthetic is applied before the procedure to reduce discomfort. The procedure causes a slight charring of stubble, and a strong odor of singed hair may result. Procedure length depends on the area that is being treated, as a small area such as the upper lip may take only a few minutes, but a large area such as the back may take several hours. Repetition also varies with the location of the procedure, and it is recommended that facial treatments be throughout one month, the chest throughout two months, and the legs throughout three months (Laser Hair Removal 2006). There are certain risks to this procedure, although complications are rare. Bleeding during the procedure and infection as a result are two of the remote possibilities, but more common side effects include darkening of the skin, which is often a temporary condition found in patients with fair skin, lightening of the skin, common in individuals with darker skin, blistering, charring, scabbing, another temporary effect, changes in skin texture, and changes in new hair growth. Often times, new hair growth has a different thickness and color (most often softer and lighter) than the hair that is lasered off. Laser hair removal is an effective and safe procedure if performed correctly and under the proper conditions in relation to skin interaction.

VI. Conclusion
Laser hair removal is an innovative procedure used throughout the world to eliminate unwanted follicles in many locations on the body. The high-energy beam of photons sent forth from a laser, operated through stimulated emission and reflection off mirrors, delivers a brief pulse that damages hair follicles and results in thinning out new growth. While the risks of using high-powered lasers on the skin are potentially damaging, the effectiveness of the procedure outweighs and surpasses previous removal methods.