”This is how the ancients described the beauty of a woman thousands of years ago, and it is evident that since ancient times, the flawlessness of the skin has been a source of fascination for people, especially yellow people. But not everyone has a fair face, due to genetic and environmental factors caused by melanocytes and melanin production abnormalities, resulting in different facial discoloration, called pigmentary skin disease. It is a common type of dermatological disorder. Although most pigmented dermatoses do not pose a significant health risk, they are cosmetically disfiguring and thus cause mental stress to patients, affecting their work, study and life. Pigment-increasing dermatoses are irregularly distributed in the skin tissue, and their lesions vary in depth, and the treatment methods chosen vary. 1.Treatment of epidermal pigment-increasing diseases In epidermal pigment-increasing skin lesions, pigment abnormalities are more complicated, mainly the following three kinds: ① the number of pigment cells increases, such as freckle-like nevus and coffee spot; ② the function and morphology of pigment cells are abnormal but the number does not increase, such as freckles; ③ only the increase of phagocytic melanocytes, such as chloasma and post-inflammatory hyperpigmentation. For the treatment of epidermal melanocyte damage (such as freckles and freckle-like nevus), 532nm, 694nm and 755nm lasers can be used to treat freckles for 1 to 3 times and freckle-like nevus for 2 to 4 times, and IPL can be used to treat freckles for 3 to 5 times, which can also achieve good results. However, due to systemic or local metabolic abnormalities such as chloasma and post-inflammatory hyperpigmentation, the effect is not good, and even the pigmentation may be aggravated after treatment, therefore, this kind of pigmentation lesion was not advocated to be treated by laser in the past. However, the C6 laser system emerged in recent years has provided a powerful means for melasma treatment. C6 selects the penetration depth of 1064nm wavelength to act directly on melasma, and breaks down the pigment substances deposited on the skin in nanometer time without damaging the epidermis, with good selectivity, as demonstrated by the black and white balloon laser in the figure below, only the black balloon inside is broken, and the epidermal barrier of the skin is not damaged. Only the black balloon inside is broken and the epidermal barrier of the skin is not damaged, so it can achieve the effect of “taking chestnuts from fire”. The laser treatment of melasma generally requires several times, with an interval of about 2-4 weeks each time, and can work normally after treatment. 2.Treatment of dermal pigmentation skin diseases The pigmentation site of dermal pigmentation lesions is deeper, usually below the papillary layer of dermis, such as nevus of Ota, nevus of Iten, nevus of cheek, etc. Because of the deep pigment location, the effect of traditional treatment is extremely unsatisfactory, and the treatment is often incomplete or leaves scar. At present, Q-switched laser is the only ideal method to treat dermal pigmented skin lesions. When treating, Q-switched laser with longer wavelength should be chosen, and the energy density should be increased appropriately to ensure that enough energy enters the dermis, causing the disintegration and fragmentation of pigmented vesicles in the dermis and discharging them out of the body, so that the damage can be reduced to a minimum. Nevus of Ota and zygomatic nevus can be treated with 755nm, 1,064nm or 694nm, etc. After treatment, the skin lesions should be grayish white, and after treatment with Nd:AG laser, there are scattered bleeding spots in the skin lesions. If there is postoperative pigmentation, the next treatment should be performed after the pigmentation has subsided, so as not to affect the penetrating power of the laser. 3, exogenous pigment treatment exogenous pigment, also known as tattoo, refers to man-made or trauma, accidents caused by pigment particles, dust into the skin tissue, can be divided into professional, amateur, cosmetic, traumatic and medical. q switch laser emergence and application for tattoo treatment provides a safe and reliable means, different pigment pigments have different light absorption peak. Therefore, the color of the laser used for treatment should be complementary to the color of the tattoo, such as red and brown tattoos treated with a 532nm laser, green and blue tattoos treated with a red 694nm or 755nm laser, and blue and black tattoos treated with a red 755nm or near infrared 1064nm laser, with a treatment interval of 3 months. Because of the advent of lasers, the treatment of pigment-increasing skin diseases such as nevus of Ota and tattoos, which were once difficult to treat and retreated by beauty seekers, has provided ideal means. It is increasingly becoming an important tool and treatment method in cosmetic dermatology.