Laser can achieve permanent hair removal, but not all hair follicles will be damaged by the laser, resulting in inactivity. If a laser hair removal session is reached, most of the hair follicles will be damaged and become inactive so that no more hair will grow. Only a small number of resting hair follicles, if not damaged by the laser, can grow hair again. The principle of laser hair removal is selective photothermal action, in the treatment process, the laser penetrates the surface layer of the skin and acts directly on the hair follicles, through the instantaneous high energy to damage the hair follicles in the anagen phase. Nowadays, the popular ice point hair removal is a gentle method to inactivate the hair follicles, so the hair follicles will not grow back after they lose their activity. However, it is impossible to inactivate all the hair follicles in the anagen stage with one laser, and several treatments are needed to damage most of the hair follicles and make them inactive, so the laser can achieve the effect of permanent hair removal, but several treatments are usually needed, usually 3-5 times or more.