Facial skin damage I. Pigmented nevus Pathological classification: Cross-border nevus: nevus cells are located in the epidermal layer of the skin, concentrated in the junction of epidermis and dermis, with deeper pigmentation and active enlargement, with the possibility of transformation into malignant melanoma. Intradermal nevus: nevus cells are located in the dermis, some of them may have hyperkeratosis and papillary hyperplasia, often with hair, clear border, and generally not malignant. Mixed nevus: nevus cells can be found in the epidermis and dermis, with the characteristics of junctional nevus, and can also be malignant. Clinical manifestations: It can occur on the face and neck and many places in the body, and it exists rarely, grows slowly, black light blue and yellowish brown. Attention is needed when the following conditions occur: enlargement of the lesion, deepening of color; hair loss, itching or painful symptoms; breakage of the surface of the mole, bleeding ulcers; appearance of satellite nevi around the lesion. Treatment methods 1.freezing treatment, 2.laser treatment, 3.surgical excision treatment (generally suitable for treatment of larger area, deeper location or uncertain nature, with reliable efficacy and steady and reliable efficacy, taking complete excision as the principle, the excision range is 2~3mm outside the lesion, paying attention to a certain depth). Not advocate the removal of chemical corrosion, because it is not easy to control the depth and size of the area, easy to scar and pigmentation damage to the aesthetic, the etiology of common lesions symptoms and common treatment methods are introduced.