By reasonably adjusting the laser wavelength, energy and pulse width, the laser passes through the surface layer of the skin and reaches the root hair follicle of the hair. The light energy is absorbed and transformed into heat energy that destroys the hair follicle tissue, so that the hair loses the regeneration ability without damaging the surrounding tissue, and the pain is slight. It can be seen that laser hair removal has become the safest, fastest and long-term hair removal technology at present.
Because in the three stages of the hair growth cycle, only the hair in the growth period can be effectively removed by the laser, which is invalid for the hair follicle in the dormant period. Because the hair follicle is in the growth stage, the hair mother cells divide rapidly. This stage has the most melanin and is very sensitive to laser. In view of the different hair growth cycles of various parts, there are obvious differences in treatment. In addition, the number of treatments was related to the hair density, color, hair follicle diameter and the proportion of non growing hair follicles in the treatment area. The density and growth of hair vary with gender, age, individual and location.
Generally, men have dense hair and grow faster than women. The hair grows fastest at the age of one year. With the increase of age, the hair density decreases and the growth rate slows down, which may be affected by endocrine regulation. In addition, the density of hair in different parts of the same individual is different. For example, the density of hair follicles in forehead and cheek is twice that of trunk and limbs. At the same time, the hair growth cycle of each part is different. These are the factors that affect the effect of laser hair removal.
The effect of axillary depilation is relatively the best, followed by bikini and limbs. Among the patients with poor hair removal effect, some patients are caused by not adhering to the whole course of treatment on time or not adhering to the whole course of treatment. Take the collar department as an example, most of them are male patients. Because of tight working hours, they can not be treated as required. Often, after treatment, the hair begins to become sparse, delaying or stopping treatment. In fact, hair follicles are not completely destroyed. After months or more, hair regenerates. In addition, due to the different hair growth cycles of various parts, patients must return to the clinic on time. Generally, the face is treated twice a week, the axillary hair is treated twice, and the trunk and limbs are treated twice a week. If the patient cannot follow the doctor’s advice and miss the best treatment time for a long time, it will lead to poor curative effect.
Secondly, the patients with poor curative effect are mostly those with darker skin color, which may be due to the specific wavelength of light released by the instrument, which is not only absorbed by melanin in hair follicle, but also absorbed by melanin particles in skin. Therefore, it is difficult to master the treatment energy of such patients, pigment particles disperse energy, and hair follicle damage is not ideal.
Thirdly, the characteristics of hair in different parts are different, resulting in treatment differences. The effect of thick black and too thick hair is not ideal. It may be that the light wave has not reached the hair follicle, but has been dispersed and absorbed by the thick and thick black hair stem on the skin surface. The hair follicles are densely distributed, and the temperature rises rapidly after light absorption, which can cause skin damage.
In addition, the hair is too thin, light and sparse, the laser energy absorption is poor, and the effect is not good. The depilation effect of limbs and armpits is better, which is related to the shallow hair follicle and the degree of destruction of hair follicle germinal cells after laser irradiation. The poor upper lip is caused by its thin hair and light color, less melanin in the hair follicle and poor absorption of laser energy.