The medical laser hair removal

In short, we will define lasers as very intense light sources emitted in a single wavelength and direction (the beam is said to be monochromatic and coherent).

Laser hair removal is less painful than electrolysis and treats all the hair on the shooting area at the same time - whereas electrolysis treats hair individually.

The principle of laser hair removal is both simple and astute: it consists in denaturing the hair bulb, but most of all the cells able to regenerate the bulb, by bringing up the temperature beyond the cell coagulation threshold, without injuring the surrounding dermis. It is called selective photothermolysis.

A bit of anatomy

Both laser hair removal and electrolysis focus on the destruction of the two structures responsible for hair regrowth. The upper third of the hair follicle, the bulge, is responsible for the generation of new hair. Indeed, it stimulates the germinal matrix at the base of the follicle. The germinal matrix can still generate new hair even once the bulge is destroyed.

Laser heat is diffused all along the stem. The whole hair structure is destroyed by the heat.

The light energy of the laser beam is absorbed by the melanin (the pigment that determines the colour of the hair) and converted into heat.

Our principal elective targets are the bulbs of young hair (in the anagen phase). Indeed, these bulbs - full of melanin - heat up significantly. The heat generated on bulbs will destroy the real targets: that is the germinal cells located in the bulge and in the matrix.

Thus, the hair is literally cauterized by itself. Just like heat denatures the structure of the egg white, which becomes white and firm when cooked, it will definitively denature the structures responsible for hair growth.

To obtain permanent hair removal, thermocoagulation must be powerful and deep enough to destroy the inferior two-thirds of the hair follicle.

What has been said before will help us answer this question. There are two possible scenarios:

1. The raise in temperature in the bulb is limited or too slow

either because the practitioner does not work with enough energy (inappropriate device, fluence too low, etc.) or has not made the correct adjustments (inappropriate pulse time, absence of clinical reactions such as erythema or papules),

or because adult or old hair bulbs are not pigmented enough, which means they do not generate enough heat, so that result is only long-lasting.

2. Heat in the hair base is high enough to destroy the bulge and the matrix, so that regrowth is not possible anymore: it is permanent hair removal. A few conditions are required:

a class IV laser able to deliver enough energy in a very short lapse of time (5 to 40 milliseconds),

the largest spot possible. The larger the spot will be, the deeper the beam will get. Thus, even the deepest hair are damaged. They will regrow more superficial and will become even more sensitive to the treatment. The spot must be at least 10mm large. Spots with a diameter of 12.5mm or, ideally, 15mm can treat the deepest hair.

a practitioner that knows what he is doing and is able to make the best adjustments and to decipher the clinical reactions linked to an efficient shooting.

The difference between permanent hair removal and long-lasting hair removal is a bit artificial. The capacity of the organism to repair its lesions is probably overcome by the repeated damage made on one same bulb. Indeed, the laser beam of a class IV laser, when handled by a specialist, will weaken the hair. It will then regrow closer to the surface. After several sessions, the hair will be irreversibly destroyed. Moreover, during such sessions, many anagen hair will be permanently removed, and long-lasting removal will be achieved on catagen and telogen hair (see The Hair Cycle). Many points will be raised further on.

SOME MORE INFORMATION: denaturation implies two types of lesions: "Hyperthermia": an overheating of the body leading to cellular damage. Hyperthermia alone can induce long lasting hair removal, but not permanent hair removal. "Coagulation necrosis": irreversible necrosis of tissue structures. The heat provokes a denaturation of proteins and the collagen. Tissues will then disappear or turn into scar masses.

Choosing the right target

Laser light, just like sunlight, penetrates into the skin up to several millimetres and turns into heat once it is absorbed by tissue pigments.

The trick consists in choosing the appropriate target, that is the target which will absorb the more light. The best target ever found is the melanin, present in the hair and in the bulb. It absorbs the laser hair removal light and turns it into heat, which leads to the irreversible necrosis of the deep structures of the hair.

Main rule in laser hair removal: use the appropriate device

Threes types of lasers are used to obtain permanent hair removal: the Ruby lasers (this gemstone produces a dark red laser light at a wavelength of 694 nanometers), the Alexandrite lasers (this semi-precious stone produces a very dark red laser light at a wavelength of 755 nanometers), and the laser diodes (semiconductors producing 790 to 810 nanometers infrared lights).

The whole treatment depends on the choice of the target and of the wavelength: all hair removal lasers target melanin. The figure opposite gives a relative idea of the absorption according to different types of lasers. (Source: Boulnois JL, photophysical processes in recent medical laser development. Published in Lasers in Medical Science Vol. I, 1986).

No options, but the best!

Only reliable material! This is the second main point concerning laser hair removal: the laser must be able to deliver enough power to destroy the bulbs irreversibly.

Class IV laser

Only a class IV laser can meet all efficiency demands. When it is meant to be used on human bodies, this very expensive laser can only be sold to physicians and used under strict medical supervision. Indeed, it can induce very severe lesions if not handled correctly.

Medical know-how consists in providing enough energy to destroy the hair efficiently without burning or damaging the surrounding tissues. This difficulty can explain the sometimes unconvincing results and the disappointment of patients treated in beauty institutes equipped with inappropriate "lasers" (and most of the time very expensive).

Flash lamps (pulsed light)

We strongly recommend you not to rely on devices such as flash lamps or other devices using pulsed light. These gimmicks - which are not lasers, but only strong lamps - are subject to unrestrained advertising. Because of a law breach which does not regulate their use, anybody can buy these devices, which are sold at very high prices despite low manufacturing costs (they are only composed of spare parts of the laser).

Many inconveniences have been reported: limited ergonomic adjustments, insufficient efficient power at the desired wavelength (which means many sessions are required to obtain any result), very low subcutaneous penetration (deep hair are not much affected), no reliable cooling system (severe burns and permanent depigmentation, etc.). In short, such devices should not be used by professionals.

Be sure to be treated by a qualified practitioner .

Pour ce qui concerne le laser, vous l’aurez compris, c’est non seulement une mesure de sécurité pour vous mais aussi tout simplement le minimum requis pour être traité avec un appareillage capable de traquer le bulbe en profondeur et détruire la matrice germinative … qui n’a aucune tendance à capituler facilement !

You have probably already understood that relying on laser is not only a safety measure but also the minimum required to be treated by a device able to find the bulb deep under the skin and to destroy the germinal matrix.which does not give up easily!

However, although the choice of the device is essential to treat the hair and its root, laser hair removal also depends much on the practitioner: the best device in the world will not give satisfying results unless it is handled by a qualified practitioner. Experience is very important in the choice of shooting parameters, that is how to obtain maximum damage on the target without injuring the skin or being too painful.

This know-how notion introduces a quite enthralling artistic dimension: the physician must take into account the phototype, the pigmentation and the diameter of the hair, the hair density, the properties intrinsic to the area to be treated, the speed of regrowth, the pulse time, the fluence, the shooting rate, the skin cooling power, etc.

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