Permanent hair removal requires the destruction of hair follicle stem cells in the bulge of the outer hair root sheath and/or the dermal papillae at the base of the hair follicle. These non-pigmented targets are located away from the melanin moieties of the colored hair shaft. In order to damage the non-pigmented targets, the heat needs to be diffused from the pigmented area to the surrounding area. This is achieved by using high energy, millisecond pulses in the red to infrared wavelengths of the spectrum that penetrate deep into the dermis and are selectively absorbed by melanin. Ruby, alexandrite, semiconductor and Nd:YAG lasers can all be used for hair removal. However, due to the lack of melanin pigment groups, these lasers are less effective on blond and white hairs. Because the epidermis has a similar absorption spectrum to the melanin in the hair follicle, laser hair removal carries the risk of epidermal damage. The light needs to first pass through the pigmented epidermis to reach the hair follicle. Skin cooling is necessary for safe hair removal treatment, which is especially important for patients with darker skin tones. The mechanism of temporary hair loss is the induction of hair into regression. The mechanism of permanent hair loss, in contrast, is achieved by two different pathways: 1. Minimizing millipore-producing terminal hairs. 2, using a pulse width of 20 ns or longer, is the complete degradation of the hair due to fibrosis. It is important to note that temporary hair loss can be achieved by using a laser with lower energy and longer pulse widths compared to permanent hair loss. For example, the 810 nm semiconductor laser or intense pulsed light source for home use has recently been reported to temporarily reduce colored terminal hairs with reliable efficacy. The ice point hair removal semiconductor laser that has become more popular in China in the last two years is better at reducing the painfulness of patients with fair results, but the recurrence rate is high and the satisfaction of doctors and patients with the long-term results is low, which is actually a temporary hair removal effect. The latest Duet semiconductor hair removal system is very characteristic, through the negative pressure attraction to make the skin stretching thinning and hair follicles close to the skin surface, which is conducive to energy transmission and thus reduce the emission energy density and reduce the patient’s pain and discomfort, the large spot treatment handle design can improve the treatment speed. Some authors have used this system to treat five male patients and observed the results against the traditional contact-cooled small spot semiconductor laser, which showed that the new Duet system has faster treatment time, higher comfort and better results. However, its long-term efficacy needs more clinical observation.