Laser hair removal machine is a laser hair removal device that manufacturers of laser hair removal equipment use the principle of selective thermodynamics to select the appropriate power, energy density and spot to treat excess hair according to different characteristics of patients.
Laser hair removal methods can be divided into 3 categories:
1. Laser hair removal without selective damage, such as CO2 laser hair removal, is time-consuming and prone to scarring;
2. Photodynamic therapy, such as oral or topical α-aminocaproylpropionic acid followed by laser irradiation, this method seems feasible in theory, but has little clinical application;
3. Selective photothermal hair removal, namely laser and intense pulsed light hair removal.
The principle of modern laser hair removal machines is based on the principle of "selective photothermolysis" proposed by American doctors Aderson and Parrish in 1983: a certain wavelength of laser light passes through the epidermis, enters the dermis, and is selectively absorbed by the hair and hair follicles. The melanin granules of the hair are absorbed, resulting in a photothermal effect, and the heat energy in the hair is conducted to the surrounding, completely destroying the "hair roots" such as hair follicles and stem cells, resulting in permanent hair removal. The normal tissue around the hair follicle does not absorb the laser because it does not contain melanin particles, so the effect is very small and generally does not cause paralysis.
When laser hair removal equipment uses the principle of "selective photothermolysis" for laser hair removal, the laser wavelength and pulse width should ensure that the laser hits the hair follicle without damaging adjacent tissues. Clinical studies have shown that the longer the wavelength, the deeper the penetration and the smaller the scattering, but the worse the absorption of melanin, the stronger the energy, but the epidermis cannot be damaged; the pulse width is smaller than the TRT (thermal relaxation) of the hair follicle. Time) is effective, and TRT larger than the epidermis is safe; the larger the spot size, the deeper the penetration; at the same time, active skin cooling should be used to protect the epidermis and relieve pain. When the wavelength is less than 600nm, the laser is mainly absorbed strongly by hemoglobin and protein, and when the wavelength is greater than 1100nm, the laser is mainly absorbed by the water in the body tissue, and the light is transparent when the wavelength is in the range of 600nm~1100nm. Therefore, people usually choose lasers with wavelengths in the range of 600nm to 1100nm for hair removal. Lasers and intense pulsed light sources used for hair removal mainly include long-pulse ruby laser (694nm), long-pulse alexandrite laser (755nm), semiconductor laser (800nm), long-pulse Nd:YAG laser (l064nm), intense pulse incoherent broadband Light source (590~1200nm), etc.
Features of Laser Hair Removal Equipment
1. Long-pulse ruby laser: wavelength of 694m, which is the shortest wavelength in clinical hair removal lasers (not commonly used at present). Short wavelength and limited penetration depth, suitable for patients with light skin and dark hair, but limited effect on deeper hair follicles. It has strong selective absorption performance of melanin, energy is not only absorbed by melanin in hair follicles, but also absorbed by melanin in epidermis, which is easy to cause epidermal damage.
2. Long-pulse alexandrite laser: wavelength 755nm, the penetration depth is deeper than that of ruby laser, it is the most common hair removal laser in clinic, the treatment effect is good, the adverse reactions are relatively few and short-lived, there are erythema reactions, skin pigmentation, folliculitis, etc. , mainly seen in patients with darker skin or due to cold compresses on the treatment area after depilation.
3. Semiconductor laser: The wavelength is 800nm, which is one of the ideal laser hair removal systems with the most clinical applications. The penetration depth is deeper than that of ruby laser and emerald laser, and hair follicle melanin absorbs photons at 800 nm relatively strongly, which can effectively destroy hair follicles. Compared with red and alexandrite lasers, epidermal melanin absorbs less energy of semiconductor 800nm laser and has relatively few adverse reactions. Semiconductor lasers have low cost, high reliability and small size.
4. Long pulse laser: wavelength 1064nm, deep penetration, so it is especially suitable for patients with darker skin. The absorption of melanin for this wavelength is reduced, the hair follicle cannot be completely destroyed, and the hair will continue to grow. At the same time, the melanocytes of the hair follicle are destroyed, and the production of melanin is reduced, causing the growing hair to turn white, so the laser hair removal equipment requires high energy. enough to destroy the hair follicle.
5. High-intensity pulsed light: High-intensity pulsed light is not a laser light source, but a non-continuous, multi-wavelength light source with a wavelength in the range of 550-1200m. Its cooling system is good, the probability of skin trauma is low, and the side effects are also small. . It takes multiple courses to achieve the hair removal effect, and its hair removal effect is slightly inferior to that of laser.
Factors of laser hair removal equipment treatment
1. Selection of laser type (ie wavelength) of laser hair removal equipment: When choosing what wavelength of hair removal laser, two factors need to be considered, one is the penetration depth of the laser; the other is the selectivity of target absorption. Due to the deep part of the hair bulb, it is decided to use a laser light source with a longer wavelength and deeper penetration for treatment. If the laser does not penetrate or penetrates too shallowly to reach the hair growth area, it will be difficult to see results. Generally, the penetration depth of laser increases with the increase of wavelength. Research shows that the ideal wavelength for destroying hair follicles is about 700nm. Another way to increase the penetration depth of the laser is to increase the spot, which can reduce the loss of the laser in the tissue and make the laser penetrate deeper into the skin. In addition, the size of the spot also affects the speed of treatment.
2. Determination of parameters: Laser hair removal is affected by various parameters such as its wavelength, spot, pulse width and energy, but the ideal value of each parameter is still unknown. According to the principle of selective photothermal action, while ensuring the selective absorption of melanin by light waves, the wavelength should be as long as possible. Theoretically, the curative effect can be improved by lengthening the laser pulse width to make it close to the thermal relaxation time of the hair follicle. Because the longer the pulse width, the less likely it is that tiny structures in the epidermis, such as melanosomes, are damaged, while relatively larger structures, such as melanosomes in hair follicles, are more vulnerable. It is generally believed that the ideal laser pulse width for hair removal should be between the thermal relaxation time of the epidermis (3-10ms) and the thermal relaxation time of the hair follicle (40-100ms).
Operation steps of laser hair removal equipment
The technical operation of laser hair removal equipment seems to be very simple, but the experience of the operator affects the treatment effect. Although the operation of each machine will vary, generally the following steps should be included:
1. Investigate the medical history, examine the recipient, analyze the skin type, and check the hair condition.
2. Turn on the power and preheat the machine.
3. Preparation of the treatment area: The hair should be shaved before treatment, because the visible hair will damage the epidermis due to the high heat caused by the laser burning, and it can also cause irreversible damage to the laser guide head and cause unpleasant odor, but mechanical equipment cannot be used. Plucking or waxing for hair removal. In addition, the area should be cleaned to remove grease and dirt.
4. Set the treatment parameters and perform the trial treatment.
5. Get the best parameters and complete the whole treatment.
6. Check the reaction after treatment, and explain the relevant precautions.