• Hair removal by laser
• Hair removal by laser references

Hair removal by laser

Laser hair removal works on a simple enough theory. The laser produces light of a specific wavelength which is applied to the skin. The light energy is absorbed by pigments in the skin and the light energy is converted to heat energy in the pigments. This heat is so intense that it effectively "cooks" the pigment containing structures. As unwanted body hair follicles are usually pigmented, they absorb most of the energy and are subsequently damaged and hopefully destroyed. Laser hair removal only works on anagen, growing hair follicles. Telogen, resting follicles have little or no pigment in the root area so these follicles largely escape damage. As a result, one laser session usually only removes about 40% of the hair. Further sessions are needed at later dates to target hair follicles that were in telogen when the first session was done. With multiple laser sessions so there is a greater hair removal effect. For the average patient, 2-4 laser sessions yields the best result. Additional sessions usually do not yield much more additional hair removal, although additional sessions may be required over the long term to maintain the hair loss effect. Although it seems lasers can permanently damage and destroy hair follicles, hair follicles are capable of regeneration to some degree. So if the follicles are severely damaged but not completely destroyed in the first few laser sessions, there may be some slow follicle regeneration after several months or years. As such, a top up session every once in a while may be needed.

Laser hair removal treatment is a relatively new form of hair removal and as such the lasers and techniques used are still evolving. In 1996 the FDA approved the use of of a patented laser process involving a so called Q-switched Nd:YAG (neodymium: yttrium-aluminum-garnet) laser. The approved technique involved an initial wax epilation and the application of a carbon bead solution (Softlight, Thermolase). The carbon bead suspension was designed to penetrate down into the hair shaft canal and act as a "chromophore". In principle, the black carbon would act to absorb the light energy from the laser and pass this energy as heat to the immediate surrounding tissues of the hair follicle. This had some merit if the hair to be removed was not pigmented, but studies have shown that this artificial chromophore provides no additional effect if the hair is already naturally pigmented. If the hair is pigmented the natural colors (melanin) will absorb the laser energy and conduct it has heat. This form of laser treatment approach has been found to give less than perfect results for the average patient. A single application of long light wavelength laser treatment has been shown in some studies to produce largely temporary hair reduction that only lasts six months or less. However, the long wavelength lasers are more effective for those with darker skin and very dark hair. In addition, long light wavelengths penetrate skin to greater depths. So long wavelength lasers are theoretically more effective in removing follicles with deep roots although multiple treatments may be required to gain a more permanent effect.

More effective laser hair removal technology was developed using ruby laser with a short light wavelength and long light pulses. This approach is most effective for light skin and lighter hair color, but much less less effective on dark, coarse hair. The short light wavelength of ruby lasers means the light energy does not penetrate the skin so well. Deep rooted hair follicles may not receive enough light energy to affected them. Published reports show a single ruby laser treatment session can be used to induce selective injury to hair follicles with a hair growth delay of at least three months and a long term reduction in hair fiber growth of 30%. With up to 4 sessions there can be 60% epilation. Because melanin pigment in the skin is readily responsive to short wavelength light from ruby lasers, there is a significant risk of skin damage for people with dark or tanned skin. Ruby laser use on dark skinned people has led to abnormal hyper (extra) pigmentation or hypo (reduced) pigmentation which is sometimes permanent.

To get the best laser hair removal results with the minimum risk of side effects, the technician or dermatologist must choose the right light wavelength and pulse duration of light for the patient's needs. Factors they will consider are the body site to be treated, the hair follicle depth of penetration into the skin, hair follicle density, hair fiber coarseness, the anagen to telogen ratio for that body area, as well as the hair and skin color and the degree of color contrast between the two. These things will determine the type of laser most appropriate, the intensity of energy applied and the duration of the light pulse. For example, hair follicle depth is deepest in the axillae, trunk, and pubic areas while it is relatively superficial on the upper lip. So, less laser energy is required to remove upper lip hair than for pubic hair removal.

In theory, the technician can choose between short, intermediate, and long wavelengths of laser light to use. A ruby laser produces a short light wavelength (694nm) and is good for removing relatively fine hair on people with Fitzpatrick skin type I-III (pale skin). Alexandrite lasers (755nm) are suitable for removing blond to light brown hair. Intermediate wavelength (800-900nm) diode based lasers are suitable for removing thicker hair with light to dark brown color in people with somewhat darker skin (Fitzpatrick skin type II-V). Long wavelength ND:YAG lasers (1064nm) are better for people with darker Fitzpatrick skin types IV-VI and relatively coarse hair fiber production that is dark brown to black in color.

Of course, most clinics do not have several different laser machines producing different light wavelengths from which the most appropriate can be selected for the patient's needs. More typically, a clinic just has one laser machine. Usually it's a semiconductor diode based laser or a new type of light source, that is strictly speaking not a laser, called an "intense pulsed light source" . Diode lasers are a good compromise, the wavelength of light produced is intermediate (800-900nm) between the short wavelength ruby lasers and the long wavelength ND:YAG lasers. The new intense pulsed light source machines (also called "flash lamps") produce a range of light wavelengths from 590 to 1200nm. Using various optical filters, the light wavelengths applied to the skin can be altered as appropriate for the patient's requirments. Diode lasers and pulsed light sources are relatively versatile and usually give the best all round results for the average patient. Reports indicate up to 75% epilation lasting 9 months with these intermediate light wavelength lasers and pulsed light source machines. However, they may not be the most appropriate laser to use for those patients who are not "average".

There are some risks involved with laser treatment mostly from ruby lasers with short wavelength light. For laser hair removal to work, the light energy is selectively absorbed by highly pigmented hair fibers and hair follicles. These structures are cooked while the surrounding, less pigmented skin, absorbs much less light energy. Because pigment is the conduit of the heat, people with dark pigmented skin may not be suitable for laser hair removal particularly with ruby lasers. Laser light contains a lot of energy and the method of hair removal involves producing intense heat in a focused area. As such, there can be some discomfort during the procedure. Depending on the laser used, the skin may be cooled before or during the application to reduce the discomfort. The skin may be sore after a session and it may itch for a few days. However, these sensations should disappear a few days after the laser session and no further problems should arise. To hel gain the best results and avoid irritating the lasered skin, it is a good idea to avoid the sun or UV light before and after treatments.

Overall, lasers can be a highly effective method to remove large areas of body hair. A single laser session, applied by an experienced practitioner who adjusts the treatment for greatest effect for each patient's particular skin and hair follicle type, can reduce hair growth by around 40%. Additional sessions, usually spaced at 4-8 week intervals, can further reduce hair growth by up to 80%. However, with more sessions there is a law of diminishing returns. The first session will be most effective and subsequent sessions will successively have less and less impact. There is still some argument about whether lasers permanently destroy the hair follicles or send them into a prolonged dormant state, but recent studies show that lasers produce a lot of damage to the hair follicle cells suggesting permanent destruction of the follicles is possible. As the cosmetic laser industry continues to evolve and new lasers along with improved application regimes are developed, so laser hair removal should become more effective and produce permanent results.

Hair removal by laser references

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