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Laser and light based hair removal

Hair removal, also referred to as epilation, is that the deliberate removal of body hairs. sorts of hair removal are practised in most human cultures since a minimum of the Neolithic era, for various cultural, sexual, medical or religious reasons. Methods wont to remove hairs have varied in several times and regions, including bleaching, plucking, shaving, waxing, threading, chemical depilatories (eflornithine) and electrolysis; these methods can not be considered ideal tools due to the limited and therefore the short-term efficacy. There has, therefore, developed an excellent demand for efficient long-term hair removal systems; actually , photoepilation by light and laser-based systems is one among the fastest growing areas of cosmetic dermatology. Only a couple of patients require hair removal for a purely medical purpose (these include patients suffering from hirsutism, hypertrichosis, acne cheloidalis nucae, pseudofolliculitis barbae), while most undergo these procedures for purely aesthetic reasons, mainly for the removal of unwanted hair from the face, trunk, limbs and genital area. If patients are suffering from medical troubles, they’re highly motivated and usually willing to undergo long and painful procedures; when the approach is only aesthetic, discomfort levels and therefore the refore the session’s duration are often important factors for the selection of the device and the pathway of treatments. especially , the genital zone is one among the foremost commonly treated body areas; the so-called ‘Brazilian look’, which involves complete removal of hairs from the vulva, perineum, anus, and buttocks, may be a particularly popular current trend. Hair removal in these sensitive areas could also be very painful with wax or other traditional devices, therefore the employment of a laser or light-based technology is usually preferred.

Lasers and lightweight based hair removal: how they work

Several laser and lightweight devices are available on the marketplace for hair removal: ruby laser (694nm), Alexandrite laser (755nm), diode laser (800nm), intense pulsed light (IPL) (590-1200nm), neodymium-doped:yttrium aluminium garnet laser (Nd:YAG) (1064nm) and light-based devices for home use.The purpose of those devices is that the damage of stem cells within the bulge and dermal papilla of the follicle by targeting melanin which represents the precise chromophore [1-3]. Melanin absorbs wavelengths between 600-1100nm, the recommended optical window for hair removal with the destruction of the follicular unit.For such devices, three main mechanisms of action are suggested: photothermal destruction, photomechanical damage and photochemical process. Photothermal destruction of hair follicles constitutes the elemental concept of hair removal: melanin, the chromophore contained inside the hair shaft, absorbs the sunshine energy converting it into heat, which spreads to the nearby bulge non-pigmented stem cells, the target. The transfer of warmth from the chromophore to the target is important for the effectiveness of the treatment. Recently it’s been demonstrated that the anagen phase is sensitive to laser and lightweight pulses exactly as within the catagen and therefore the telogen since in humans the hairs remain pigmented during the entire hair cycle. For this reason, targeting the hair follicles during a selected growth period, is taken into account to be unimportant. The previous theory about the greater sensitivity of the anagen period was thanks to animal studies which showed a maximum concentration of melanin within anagen hairs [2-5].Photomechanical destruction, through the generation of shockwaves, has been employed by nanosecond Q-switched lasers, employed during the first phase of laser hair removal several years ago; these lasers are not any longer considered because they end in temporary hair loss. Photochemical destruction, through the creation of toxic mediators like singlet oxygen or other free radicals, is that the approach followed by photodynamic therapy (PDT); this might be a possible alternative technology since it’s going to also work on non-pigmented hairs.

Lasers and lights
IPL : IPL technology uses a xenon broadband flashlamp to get non-coherent light during a spectrum between visible and near infrared (500-1200nm). to succeed in the specified chromophore, filters cut out the sunshine emission consistent with the wavelengths required by the physician; consequently, this sort of sunshine source can excite quite one chromophore (haemoglobin, melanin, water). Handpieces have an outsized surface of the spot, which is usually cooled, and application of gel on the skin surface is required during epilation. Clinical endpoints, frequently seen during epilation by lasers, aren’t commonly observed with IPL. Various studies have shown that IPL is inferior to Alexandrite and Nd:YAG lasers for long-term results [6-14].
Nd: YAGNd-YAG long pulse may be a laser source with a extended wavelength and represents the primary choice in darker skin patients in our experience. consistent with several comparative studies Nd:YAG laser has been found to be less effective than Alexandrite and diode lasers, and more efficacious than IPL and ruby laser as regards long-lasting hair removal results [6-14].Diode laserHistological studies showed significant reduction in hair density and thickness in skin treated with longer pulse 810nm diode laser. The long pulsed diode has been greatly used for hair removal thanks to the efficacy and safety in patients with Fitzpatrick skin phototypes I-V. Such lasers are usually employed through an in-motion manner, with several short pulses and a high frequency. Patients often consider this laser more tolerable than the long pulsed Nd:YAG [6-14].Alexandrite laserSince 1997 the long pulse 755nm Alexandrite laser has been utilised with efficacy in laser hair removal. It allows a deep penetration into the dermis allowing it to act on fair and black hair, however, due to its competition with melanin it’s particularly indicated in patients with low phototypes (up to 3-4) for the danger of burning leading to hyper or hypo pigmentation. so as to remedy this problem a replacement technology for photoepilation has recently been proposed.

A new handpiece, with a cooled sapphire cylinder tip that conveys the beam onto the patient’s skin, has been introduced onto the market. the utilization of this sapphire guide dramatically reduces the system energy leaks to the skin, thus increasing effectiveness of the laser transmission as never before (Figure 1). performing at low fluences makes the treatment painless without undesirable side-effects. Repeated passages over an equivalent area makes the treatment uniform without leaving any area untreated.Ruby laserThis was the primary laser device selectively employed for hair removal, by Grossman in 1996 [15]. Compared to newer laser and light-based modalities, the ruby laser is a smaller amount effective and actually there are not any long pulsed ruby lasers commercially available within the American market. Side-effects, like hypopigmentation, are reported after its use on dark skin.Home devicesHome devices are characterised by lower fluence compared with medical devices; this feature limits their effectiveness, since there’s evidence of the potential of hair removal systems being fluence-dependent. Conversely, the risks of adverse effects are reduced too. Nevertheless, the overall public often prefer investing their money into these tools because they’re cheap and pain free.

Clinical features of the patient
The main features to be evaluated are skin phototype and hair. Shorter wavelengths are more absorbed by melanin, so for top phototypes lasers with a coffee wavelength will end in a greater risk of burning and consequently other unpleasant side-effects; for these patients the choice of a diode laser or Nd:YAG laser is mandatory. If the physician features a limited choice of laser systems, it’s possible to use a lower fluence, a extended pulse duration and a selected filter to form the treatment safer. Sometimes, for various reasons, patients can’t be treated with lasers or IPL devices (Table 1).

Preparation for the treatment
It is necessary to remind the patient to avoid all epilation techniques for 2 to four weeks before the laser / light hair removal, otherwise it’ll provoke elimination of the structure target of the photoepilation. Shaving the hair by the physician immediately before the start of the treatment, or two to 3 days earlier by the patient, is adequate. If the laser / light hair removal isn’t preceded by shaving, the pulses absorbed by the long hairs could induce burning of the skin. We usually like better to do the shaving ourselves, since we will better evaluate the diameter and therefore the pigmentation of the hairs cut, andthese features affect the parameters to be chosen.

Selection of the parameters
The fluence (J/cm2) determines the temperature achieved within the follicular stem cells within the bulge while the heart beat duration corresponds to the time length of that reached temperature. The energy state , the fluence, changes for every laser and IPL device consistent with their output range features, however, the physician should select the very best value without eliciting side-effects within the skin, since high fluences are correlated with greater permanent hair removal. Normally, the fluence is inversely proportional to the pigmentation of the hairs to be removed, e.g. darker hairs require lower fluence while brighter hairs need higher fluence.According to the selective phothermolysis theory the heart beat duration should approximately correspond to the thermal time constant (TRT) of the chromophore, except for laser-based hair removal the chromophore, melanin, and therefore the laser biological target, stem cells of the follicle bulge, don’t correspond. this needs a laser pulse duration longer than if the chromophore and therefore the target were identical; we apply the concept of thermal damage time (TDT), allowing the conduction of thermal damage to the follicular stem cells. As a result, 10-100ms laser or IPL pulses are usually needed, while shorter pulse times are indicated for thinner hairs.
In the cases of dark phototypes the heart beat duration should increase for achieving a kind of epidermal protection to all or any the possible risks. The patient with a high phototype with thin and bright hairs presents a significant challenge for hair removal practitioners, as this sort of hair would require an excellent fluence and a brief pulse whereas the skin type would require a coffee fluence and an extended pulse duration.Another relevant fact to be considered is that the progressive reduction of the hair diameter with the laser / light sessions, therefore the physician may have to vary the parameters getting used .The spot size influences the penetration depth of sunshine , since a much bigger spot size penetrates deeper for a reduced scattering phenomenon. a bigger spot size allows the practitioner to hide the world to be epilated rapidly, but this will cause increased discomfort for the patient thanks to the possible unpleasant sensation on a bigger a part of the body [16-18].

Treatment protocol
During the treatment, the laser / light emission should be matched with a cooling system; this is often important for all phototypes, but vital in those persons with more epidermal melanin. Cryogen spray, cold air, and direct contact cooling are commonly employed together with lasers and IPL [19].

Clinical endpoints
Clinical therapeutic endpoints are immediate or early cutaneous reactions that happen during a laser session; they’ll guide the physician in delivering safe and effective laser / light treatment. the foremost relevant clinical endpoint for laser and IPL hair removal is perifollicular erythema and oedema, which corresponds to an eosinophilic inflammatory reaction thanks to the hair injury. This endpoint typically appears a couple of minutes after the laser / IPL passage and this immediate skin response gives evidence of the effectiveness of the treatment.The pigmented hairs vaporise releasing a typical smell of smoke thanks to the burnt keratin. the skinny hairs behave during a different manner after the laser / light emission: they will enlarge the tip or turn white at the follicular ostium.

Results
A permanent dropout of hair follicles is reached in 15-30% of laser / light treated hairs at each session, while the bulk of treated hairs fall under a telogen-like state characterised by rest and absence of hair growth. This telogen-like state explains a short-lasting period of alopecia, usually lasting for a couple of months, until some hair follicles begin another anagen cycle. Erythema frequently occurs and therefore the employment of a topical steroid for 2 to 3 days is enough to eliminate this temporary side-effect. The patient should remember to avoid sun exposure and to use sunscreen for several days days following the session.

Possible side-effects
The most common cutaneous reactions include erythema, oedema, discomfort, pain, and infrequently more severe side-effects, like thermal burns, blisters, hyperpigmentation, hypopigmentation and scarring, can occur. Severe side-effects manifest more frequently in darker-skinned patients but are often avoided or minimised by the choice of safer parameters and an efficient cooling process during the session. ‘Paradoxical hypertrichosis’ may be a rare side-effect observed in patients treated by IPL, diode and Alexandrite lasers, when the laser or light stimulates the expansion of latest hairs through a photoactivation of dormant hair follicles into terminal anagen hair phase. it’s characterised by the looks of latest hair follicles surrounding the treated areas. This side-effect might be induced by the choice of excessively conservative parameters, and thus it are often solved by more aggressive parameters during the next sessions [20-21].

Conclusion
Laser hair removal may be a popular treatment, and thus its techniques are evolving. consistent with previous comparative studies laser and light-based systems for hair removal are shown to be generally safe and efficacious if employed by experienced practitioners. The differences between these systems include the time length of each session, the discomfort felt by the patient, the likelihood of treating darker patients, and therefore the cost of one treatment. New hair removal systems could include promising portable home devices, photopneumatic technologies, PDT and bipolar radiofrequency. Clinical studies and long-term data are going to be necessary to work out the effectiveness and therefore the safety of those modalities from the longer term .

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