The most commonly used laser for dark removal is the Q-switched laser. This laser emits a specific wavelength of laser beam with a very high peak power, which is absorbed by the pigment and the pigment is crushed by the photothermal effect, the pigment mass is rapidly expanded and broken, and then these small fragments are gradually engulfed by phagocytes in the body and cleared out of the body. In addition, due to the extremely short time of releasing energy, as short as a few tens of nanoseconds, so that the heat generated is not In addition, due to the short release time, as short as a few tens of nanoseconds, the heat generated is not transmitted to the surrounding tissues and epidermis, causing no damage to the normal skin, and thus no scars are formed in principle after treatment. Indications for black laser treatment: pigmented mother spots, freckles, age spots, brown spots, coffee spots, nevus of Ota, acquired nevus of Ota, tattoos, eyeliner, eyebrow washing, etc. The course of black laser treatment: generally, nevus of Ota needs to be treated 3-7 times, once every 6 months; freckles, age spots and tattoo washing need to be treated 1 to 3 times, once every 3-6 months. Precautions after treatment: 1. There is a burning sensation after laser treatment, so ice can be applied to reduce the discomfort. 2.After laser treatment, there is slight skin rupture and exudation, avoid getting wet, and apply anti-inflammatory ointment topically. 3, 7 to 10 days after treatment, the surface scabs fall off naturally, after at least 2 months should avoid sun exposure.