Laser epilation: the mechanism of action, the technique of conducting, indications and contraindications

In the early 1990s, there was a revolution in the field of hair removal, which is associated with the beginning of the use of the first lasers.

Laser hair removal is a method of removing hair with a laser beam. At the heart of the technique of laser hair removal is the thermal effect, which is created by the absorption of light by the melanin of the hair. Laser radiation absorbed by the melanin of the hair causes heating of the hair shaft from which the adjacent follicular epithelium is heated. The most suitable for epilation radiation give the following lasers: ruby, alexandrite, neodymium and diode. These lasers differ in the wavelength of the emitted light, as well as in the radiation energy and the duration of the pulses. Depending on the parameters of the laser, damage to the follicle can be photomechanical (in the case of a neodymium laser, when the main destructive factor is the rapid expansion of tissue upon heating, or photothermal, when coagulation, carbonization, or vaporization occurs.

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Apparatus for laser hair removal

Ruby laser generates red radiation with a wavelength of 694 nm - at the maximum absorption by melanin. Hemoglobin absorbs weakly at a given wavelength. A long-pulse ruby laser produces light pulses of about 3 ms duration, providing a flow of energy up to 40-60 J / cm ². There is information about the use for ruby laser epilation with a pulse duration of 0.5 ms (energy flux up to 20 J / cm ² ). The pulse repetition frequency of a ruby laser is usually about 1 Hz (one pulse per second), i.e., it is a relatively slow acting laser.

Since the target for this type of laser is exclusively melanin, this type of hair removal is not applicable for tanned skin, as well as for light hair. The effectiveness of hair removal is increased for skin types I and II according to Fitzpatrick in combination with dark hair.

The Alexandrite laser generates radiation with a wavelength of 725 nm, i.e. Also in the region of minimal hemoglobin uptake and strong uptake of melanin. The pulse duration is 2, 5, 10 and 20 ms. Alexandrite is a faster laser than ruby laser, because the pulse repetition frequency is several times higher - about 5 Hz. The energy flow on the tissue is 10 J / cm ² per pulse in a laser pattern up to 10 mm in diameter. Restrictions on skin types and hair color in alexandrite laser are the same as for ruby.

The diode laser generates invisible light at a wavelength of 800 nm in the near infrared spectrum, i.e. Also in the region of strong uptake by melanin. The pulse duration is from 5 to 30 ms, the frequency is 1 Hz, the energy flow on the tissue is 10-40 J / cm ² in a laser pattern 9 mm in diameter. A diode laser, like a ruby laser, can not provide effective epilation of light and red hair, as well as hair on tanned skin.

Neodymium laser, or a laser on an aluminum-yttrium garnet, is widely used in medicine to remove tattoos. Generation of laser radiation is carried out on the transitions of neodymium (Nd3 +) ions, which are built into yttrium-aluminum garnet-YAG crystals. Therefore, such a laser is often called the "Nd: YAG laser". Nd: YAG laser emits in the near infrared range (1064 nm). This radiation is minimally absorbed in the upper layers of the skin and penetrates into the deep layers. The pulse duration is of the order of 100 ns, that is, much less than for other laser types.

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Photoepilation

In recent years, there has been an alternative opportunity to make hair removal using the method of photoepilation. The method is based on the principle of selective photothermolysis. In accordance with this principle, the melanin of the hair absorbs light energy, which is then transformed into thermal energy, which ultimately leads to the destruction of the hair follicle. Photoepilation uses a broadband light source, or a source of nonmonochromatic light. Intensive light pulses are generated - from 400 to 1200 nm, overlapping the visible and near infrared wavelength ranges, i.e., in the region of strong uptake by melanin. Unlike lasers, the light pattern on the skin is a rectangle measuring 4.5 to 10 cm ², depending on the manufacturer. So, for example, "SPA TOUCH" firm "Radiansi" uses the patented technology LHE (Light Heat Energy - light-energy energy), in which light and heat are combined. About 85% of the coagulation is performed by heat, and the remaining 15% by light. In order to penetrate into the follicle and coagulate the hair bulb, the SPA optimizes the following 3 parameters: wavelength - 400-1200 nm, spot size - 55x22 mm and pulse duration - 35 ms. The device «SPA TOUCH» has the largest working area size in comparison with other devices on the market. This allows to carry out the procedure on large areas, for example, the time spent on processing two shins is only 40-60 minutes. For comparison, the approximate time required for electrolysis is 4 to 6 hours for the treatment of one leg, and laser hair removal from 1 to 2 hours for treatment of both shins.

Unconditional advantages of photoepilation are insignificant soreness, non-invasiveness of the technique and the possibility of immediate effect on a group of follicles. After the procedure, the hair falls out within 10-14 days. Photoepilation can remove even the blondest hair. Red and gray do not practically react to photo-exposure. Therefore, such hair is removed by electrolysis. Multiplicity of procedures depends on many factors: from the epilated zone, the speed of hair growth, age, etc. Indication for photoepilation is ingrown hair, not only in women, but also in men. After the first treatment, the number of folliculitis is reduced by 60-70%.

Contraindications for performing laser or photoepilation procedures

Absolute contraindications include: sunburn (procedures can not be performed within 28-35 days after the last insolation), become pregnant, mental illnesses (in particular epilepsy), severe somatic diseases in the stage of decompensation, herpetic infection in the acute stage, open skin lesions, tumors, taking phototoxic drugs (systemic retinoids, tetracycline antibiotics, etc.).

Relative contraindications include: age less than 18, hirsutism and hypertrichosis, propensity to keloids and hyperpigmentation, photodermatosis.

When performing laser or photoepilation, you may encounter side effects such as erythema and skin edema at the site of the procedure, pigmentation disorders (hyper- and hypo-), transient angiectasias.

Very often it is necessary to use a combination of several epilations in one patient. After several procedures of laser or photoepilation, a change in the structure and color of the hair is observed. Therefore, customers wishing to continue hair removal, electrolysis is performed. After the completion of the procedure, the doctor should tell you the features of care for the treated area. When performing epilation on the face, you need to use a cream with a sunscreen factor to avoid the development of hyperpigmentation. Between the procedures, the hair can only be shaved or cut, but in no case plucked and waxed.

[5], [6], [7],