Laser hair removal uses the selective photothermal action of the laser to instantly destroy the hair follicles and play a role in inhibiting hair growth, which can usually be maintained permanently. However, there are two points that should be noted, one is that laser hair removal treatment requires several times, usually 3-5 times to achieve permanent hair removal effect. Secondly, permanent hair removal does not mean that there is not a single hair on the skin. The current laser technology can not reach the state of hair elimination, can only remove more than 90% of the hair, after doing so, there will be fine and soft small hair, is also the ideal treatment results. The growth cycle of hair follicles is different, there are growth period, resting period and dormant period, laser hair removal can only work on the growth period hair follicles, can not affect the resting period hair follicles. Therefore, it is difficult to achieve permanent hair removal effect with one laser treatment, and it should be carried out in several times. The interval of laser hair removal is generally 1-1.5 months, and the number of times of hair removal treatment is also different for different parts of the body with different hair thickness, and underarm hair removal generally requires 5 times to achieve a more ideal state. Some parts of hair growth are regulated by hormone levels, such as beard and pubic hair, which may still grow after treatment, and the effect is somewhat deviated.