by: DR Neda Adibi Dermatologist

The growth of unwanted and terminal hairs in androgen dependent area in the

females called hirsutismThe etiology is either idiopathic or due to

androgen excess

(1 )The damage may result from direct direct photothermal destructionphotothermal destruction, whereby a light source emitting a wavelength in the absorption spectrum of the

desired chromophore melanin (600–desired chromophore melanin (600–1100 nm) 1100 nm) results in selective heating of the hairselective heating of the hairshaft, follicular epithelium, and hair matrixshaft, follicular epithelium, and hair matrix...

The laser emits a gentle beam of light which is absorbed only by the hair follicle

(leaving the skin unharmed). This light energy is transformed to heat which

destroys the hair follicle permanently. That’s really all there is to it .

This is called ‘Selective Photothermolysis .’

The laser emits a gentle beam of light which is absorbed only by the hair follicle

(leaving the skin unharmed). This light energy is transformed to heat which

destroys the hair follicle permanently. That’s really all there is to it .

This is called ‘Selective Photothermolysis .’

AnagenAnagen follicles of terminal hair extend deeply into the subcutaneous fat, lying 2–7 mm lying 2–7 mm below the skin surface.

The bulb of a telogen, or club, hair is unpigmented because of the cessation of melanin production during the

catagen stage. In fact, the cessationof melanin cessationof melanin

production is the first sign of production is the first sign of catagencatagen.

As anagen progressesAs anagen progresses, the bulb and papilla

descend deeply descend deeply into the dermis so that late

anagen hairs may also be somewhat laser resistant laser resistant to treatmentto treatment. It would seem

,therefore, that it is in early anagen that hair follicles early anagen that hair follicles are most sensitive to laser induced injuryare most sensitive to laser induced injury. Since

any any injuryinjury, even a laser injury, may , even a laser injury, may

induce induce telogentelogen, the timing of a second laser second laser treatment treatment after the first laser induced telogen formation,

becomes critical. As the laser resistant terminal laser resistant terminal follicles now enter an anagen growth phasefollicles now enter an anagen growth phase,

after a first treatment, the second treatment may be more more effective effective than the first. Conversely, a second treatment second treatment given too early, or too late, would be expected to have given too early, or too late, would be expected to have little effectlittle effect.

Lin et al postulate that follicles treated in the follicles treated in the telogen phase show phase show only a only agrowth delay for weeksgrowth delay for weeks, whereas, when those follicles are treated in the anagenanagen phase they may be susceptible to phase they may be susceptible to lethallethal damage, may have a growth delay, or may simply switch into telogen switch into telogen phasephase. This could partly explain the growthdynamics of the hair cycle. Repeated treatments could lead to a synchronizationsynchronization of the anagen phase by induction and/or of the anagen phase by induction and/or shortening of the telogen phase,which could increase the shortening of the telogen phase,which could increase the effiveness effiveness of hair removal with

Another explanation might be that the follicle is not destroyed immediately, but shows a growth arrest after only one growth arrest after only one (shortened) anagen cycle(shortened) anagen cycle. Some have questioned the assumption that effective laser hair removal is determined solely by treating hairs in the anagen cycle. These investigators suggest that melanin within a hair follicle may be moremelanin within a hair follicle may be more important than the actual time of treatment.

Permanence, defined as an absolute lack of hair in a Permanence, defined as an absolute lack of hair in a treated area treated area for the lifetime of the patient, may be an unrealistic unrealistic goalgoal .

Dierickx et al. have suggested a more practical approach. They defined ‘permanentpermanent’ hair loss as a significant reduction in the number significant reduction in the number of terminal hairsof terminal hairs, after a given treatment, that is stable for a stable for a period longer than the complete growth cycle of hair period longer than the complete growth cycle of hair follicles follicles at any given body sit

Permanent hair reduction is defined by the FDA as stable stable decrease in the number of terminal terminal hairs for a period longer than a period longer than the complete hair cycle the complete hair cycle at a given site following a treatment regime, which may include multiple sessions.

1.Laser induces catagen induces catagen phase 2.One of the uncertainties in laser hair removal is the exact tissue

target. it appears that complete destruction of hair follicle without regeneration potential may occur when both the germinative cells germinative cells in the bulb and the stem cellsstem cells in the bulge area are destroyed. As follicular stem cells appear to be very stem cells appear to be very resilient to thermal damageresilient to thermal damage, this may be diffi cult to achieve

It should be noted that there is a general consensus that hair removal results will always be affected by chosen anatomic site.

Most investigators note a better better response on chest, chest, face, legs, and axillaface, legs, and axilla .

Lesser Lesser responses appear to occur on the back, upper back, upper lip, and scalplip, and scalp. In addition, terminal hairs, and not not vellus vellus hairs respond to laser treatment.

The ideal patient ideal patient has realistic expectations, normal endocrine normal endocrine status, with thick dark hair and light skin toneslight skin tones .

There are differences in the anagen:telogen ratio depending on the area that is treated. For example the axillae and bikini areas have areas have a higher anagen: telogena higher anagen: telogen ratio than the legs, arms, and legs, arms, and chestchest. Therefore, it has been suggested that these areas would respond better to laser hair removal with more noticeable difference .in hair density

It is now widely accepted that almost any laser can induce temporary hair loss.Fluences as low as 5 J/cm 2 can induce this effect. The effect tends to last 1–3 months.

The mechanism of action appears to be an mechanism of action appears to be an induction induction of catagen and telogenof catagen and telogen.

PermanentPermanent hair reduction, occurring at higher higher fluefluencesnces is seen in 80% of individuals and is fluence

dependent. Thus, the greater the delivered fluencethe greater the delivered fluence,

all else being equalall else being equal, the better are the the better are the expected resultsexpected results..

DarkDark hair with ample amounts of eumelanin ample amounts of eumelanin can be effectively treated by multiple devices, provided that appropriate fluence and spot size are used. Under these conditions, the the average long term hair loss per treatment is about 20-average long term hair loss per treatment is about 20-30% 30% based on studies performed with ruby lasers.

Multiple treatment sessionsMultiple treatment sessions are usually required to achieve the maximal level of hair reduction.In individuals with blonde, red, gray, or blonde, red, gray, or white hairwhite hair, it is unlikely that laser treatment will produce the same degree of longlasting hair removal. However,

such patients may be willing to undergo treatments spaced treatments spaced about 2-4 months apart as necessary to about 2-4 months apart as necessary to maintain temporary hair lossmaintain temporary hair loss.

While treatment can be safely performed with a shorter shorter wavelength device (e.g. ruby laser) in fair wavelength device (e.g. ruby laser) in fair skinned patients, it is preferable to use longer longer wavelength devices in darkerwavelength devices in darker skinned patients.

The first laser hair removal system employed was the

normalnormal-mode ruby laser, but the pulse duration of 0.3 mspulse duration of 0.3 ms was

not efficacious longer pulse durations of 0.7-0.8 longer pulse durations of 0.7-0.8 ms ms subsequently increased its usefulnessincreased its usefulness. When the pulse duration of the ruby laser was lengthened to 3 ms, 3 ms, permanent permanent hair removal was demonstrated however,

there was a significant risk of dyspigmentationdyspigmentation. In generalIn general, use of the ruby laser for hair removal is

limited to patients with skin types I-IIIskin types I-III, since absorption of

694 nm light by epidermal melanin results in a higher risk of compli-

cations (e.g. blistering, pigmentary changes) in individuals with darklypigmented skin.

BOLOGNIA:Multiple studies have demonstrated effective hair removal with thelong-pulsed alexandrite laser at fluences of 10-40 J/cm2 and pulse durations of 2-20 mspulse durations of 2-20 ms. At fluences of 20-40 Jlcm2, several investigators have reported hair reductions of 70-80% after multiple (at least 3-5)multiple (at least 3-5) treatments. Use of the long-pulsed alexandrite in patientswith darkly pigmented skin has been reported, but side effects such asblistering and pigmentary alteration can occure in general, this laser isbest suited for hair removal in patients with skin types I-III.

Red hair Red hair contains pheomelanin, which absorbs poorly at any wave-length, but especially beyond 800 nm. Therefore, shorter shorter

wave-lengthswave-lengths, such as those of ruby or ruby or alexandrite alexandrite lasers are needed in these patients.

In cases of low contrast between skin tone and low contrast between skin tone and hair colorhair color, such as darkly pigmented individuals or light hair in fair individuals, a significant portion of emitted light is significant portion of emitted light is absorbed by the epidermal melaninabsorbed by the epidermal melanin. This occurs because

epidermal melanin absorbs energy not only from direct direct exposureexposure, but also from backscatteringbackscattering. As

wavelengths of light increasewavelengths of light increase, a greater ratio a greater ratio of dermal-to-epidermal depositionof dermal-to-epidermal deposition of energy results

in greater safety greater safety in such individuals.

Diod:Both 800 and 810 nm wavelengths are absorbed by melanin absorbed by melanin to a slightly lesser degree compared to the alexandrite to a slightly lesser degree compared to the alexandrite laserlaser . .

Absorption is also approximately 30% less than that of the Absorption is also approximately 30% less than that of the

694 nm wavelength. 694 nm wavelength. Decreased absorption Decreased absorption by epidermal melanin permits by epidermal melanin permits safe treatment in patients with safe treatment in patients with skin types I to IVskin types I to IV .

Although the rates of melanin absorption by diod laser is lower than the

ruby and alexandrate, the rates of hair reduction with the rates of hair reduction with the diode laser are similar to those the diode laser are similar to those observed with the alexandrite laserobserved with the alexandrite laser, likely due to deeper penetration into the dermis deeper penetration into the dermis . Treatment with the

diode laser can be somewhat more painfulmore painful, however, at least partly due

to greater volumetric heating of tissuevolumetric heating of tissue. If

necessary, pain can be partially alleviated by pain can be partially alleviated by reducing the frequency of delivered pulsesreducing the frequency of delivered pulses .

A diode laser was safely used in several patients

undergoing isotretinoin therapy without undergoing isotretinoin therapy without increase in adverse effect or longterm increase in adverse effect or longterm sequela,the isotretinoin use should be avoided sequela,the isotretinoin use should be avoided in general up to 6 month beforehair removalin general up to 6 month beforehair removal..

Laser treatments for hair removal are generally well tolerated bypatients and do not usually require anesthesia. However, because the hair follicle is surrounded by nerve

endings, topical anesthesia is necessary when anesthesia is necessary when treating large surfaces of the body or treating large surfaces of the body or sensitive areas such as the upper lip and sensitive areas such as the upper lip and bikini areabikini area. Local infiltration of anesthetic or nerve blocks using 2% lidocaine can also be useful in selected patients.

Pulses are delivered in a slightly overlappingslightly overlapping mode with a predetermined spot size. The ideal immediate response is vaporization of the hair shaft, followed

erythema a few minutes later by the appearance of perifollicular edema and

fluencefluence and the It is generally recommended that the the highest tolerablehighest tolerable

largest spot size largest spot size be used in order to obtain the best results .

Larger spot size may accelerate the response

,excessive fluences that cause epidermal separation or

blistering should be avoided. If the device is not equipped with a cooling mechanism, a thick layer of cool gel is applied before the delivery of laser pulses.

Epidermal cooling Epidermal cooling during treatment accomplishes two goalstwo goals .

First, it minimizes the risk of epidermal damage First, it minimizes the risk of epidermal damage due to absorption by epidermal melanin. Such damage may result in

blistering, discoloration, and scarringblistering, discoloration, and scarring, and is especially important for darker pigmented individuals. Therefore, epidermal cooling allows for use of higher fl uences while minimizing the risk

of epidermal damage. Second, it has temporary Second, it has temporary anesthetic effectanesthetic effect, thus reducing patient discomfort during treatment. Epidermal cooling can be separated into contact and non-contact. Contact cooling may include cold gel, chilled sapphire window, and cooled copper plate. Non-contact cooling includes cold air convection and dynamic cooling with automatic spraying of liquid cryogen, tetrafl uoroethane, immediately prior to laser pulse.

After being scattered, photons closer to the center closer to the center of the beam may, in fact, regain the initial direction of travel regain the initial direction of travel through their interaction with other photons. On the other hand, if scattered, photons at the peripheryphotons at the periphery of laser beam may not be not be able to regain itable to regain it. Therefore, the percentage of light the percentage of light lost to scattering is larger for smaller beam lost to scattering is larger for smaller beam diameterdiameter, or spot size, than for a larger one. Two corollaries of this principle are that energy density, or fl uence, is lowered for larger spot sizes and that a very small spot size may, in fact, not allow for suffi cient depth of penetration, even with longer wavelengths. Thus, the largest spot size accommodated by the size of the treatment area may lead to better effi cacy, as well as decreased overall treatment time.

,the choice of fluence depends on the the choice of fluence depends on the amount of chromophoe in the target structureamount of chromophoe in the target structure,

as well as selected wavelength.as well as selected wavelength. Higher fl Higher fl uences are needed when the amount of uences are needed when the amount of chromophore is reducedchromophore is reduced, as represented by blonde blonde or thinner-caliber hairor thinner-caliber hair. As well, as was previously discussed, higher fluences are used with longer wavelengths due to the nearly linearly decreasing absorption of light by melanin at those wavelengths. In addition, fl uences diminish rapidly as a function of the depth of penetration, as progressive absorption and scattering result in decay of the original energy. Therefore, even though

temporary hair removal will occur at almost any fluence, higher higher fluences may result in longer- fluences may result in longer-lasting or more permanent hair lasting or more permanent hair reductionreduction.

For all laser and light systems, the immediate treatment treatment endpoint is vaporization endpoint is vaporization of the hair shaft. This is

followed in a few seconds to minutes by mild followed in a few seconds to minutes by mild erythema and perifollicular edemaerythema and perifollicular edema .In general, these should resolve within 10 to 60 minutesshould resolve within 10 to 60 minutes .

More widespread erythema or confluent edema may More widespread erythema or confluent edema may indicate epidermal and dermal damageindicate epidermal and dermal damage, respectively. If noted, lower fluence, longer pulse duration, or better cooling should be utilized.

Gray or white discoloration Gray or white discoloration immediately following laser

pulse and lasting a few seconds few seconds is an indication of

epidermal damage epidermal damage and should be avoided.

Research has shown that laser hair removal requires the laser hair removal requires the presence of a pigmented hair shaftpresence of a pigmented hair shaft. Retreatment can therefore be performed as soon as regrowth appearsas soon as regrowth appears.Regrowth is based on the natural cycle, which varies by anatomic location,

but on average, the timing is 6–8 weekson average, the timing is 6–8 weeks. More research regarding this is currently being conducted.

RepeatedRepeated treatments may synchronize the anagen synchronize the anagen phase by inductioninduction and/or shortening of the telogen phase shortening of the telogen phase which could lead to increased effectiveness of hair removal at each consecutive treatment. Alternatively, the follicle may show growth arrest after one shortened anagen cycle

Temporary hair loss (1–3 months) Temporary hair loss (1–3 months) always occurs after laser treatment, regardless of hair color or device used. On the other hand, the ability to induce long-lasting hair reduction is strongly long-lasting hair reduction is strongly

correlated with correlated with hair colorhair color. Patients with dark hair dark hair are most likely to obtain longlasting hair removal. Blonde-, red-, gray-, or white-haired patients are unlikely to experience a permanent reduction, because melanin is low or lacking in the hair follicles.