The 585nm laser emitted by the pulsed dye laser can penetrate the epidermis and enter the dermis where there is an abnormal dilated vascular network. The hemoglobin inside the blood vessels in the lesioned area absorbs the laser energy and is thermally coagulated, and these coagulated hemoglobin will close the abnormal blood vessels, as a result, the lesioned blood vessels in the nevus will disappear and thus be cured. Since this laser hardly damages the skin, there is no scarring after the treatment and the original color of the skin can be completely restored. However, the lesioned blood vessels are distributed in three dimensions under the skin, so each laser treatment can only remove part of the blood vessels, and a few blood vessels will be reopened after the treatment, so the treatment often needs to be carried out several times to make the red spots fade gradually. It is worth noting that as the age of the nevus grows, the color of the nevus will gradually deepen and the lesion will thicken, which makes the complete treatment difficult. Therefore, doctors suggest that bright red nevus should be treated as early as possible. 2. Indications for laser treatment: hemangioma, nevus, keratotic hemangioma, capillary dilation, rosacea, spider nevus, pyogenic granuloma, hyperplastic scars, scars, etc. 3.Laser treatment course: usually 5~8 times, and the interval between each treatment needs more than two months. Precautions after treatment: 1.After treatment, there is a local burning sensation, ice should be applied to prevent blistering. 2.After treatment, local edema of different degrees of skin will occur, and even exudation crust and small blisters will occur, so water should be avoided and anti-inflammatory creams should be applied externally. These reactions will subside in about 7~10 days. 3. Avoid sun exposure for 2 months after treatment. Individual patients may experience hyperpigmentation, which usually disappears on its own within a few months and requires no special treatment.