Scarring can be treated by laser, but is it possible with all types of lasers? There are many different types of lasers, but the mechanism of action of a normal laser is to use its powerful energy and precise directionality to rapidly burn and vaporize the lesion, thereby clearing it away. It is indisputable that while the lesions are cleared, the normal tissues are also “eliminated” at the same time, therefore, using ordinary laser treatment will inevitably leave new scars, and the pain is severe and painful. So, is there any way to clean up the lesions without damaging the normal tissues, thus reducing the pain and leaving no scars? Thanks to the tireless efforts of laser research experts, this problem has finally been solved perfectly – she is the pulsed dye laser. The wavelength of 585nm or 595nm pulsed dye laser, through the principle of selective photothermal effect, the laser penetrates the epidermis and acts on the lesioned blood vessels in the dermis, and the heat energy in the laser is absorbed by the hemoglobin in the blood vessels, causing the lesioned blood vessels to coagulate to treat the vascular lesions. The surrounding normal tissue is not damaged. Since the early 1990s, scientists have been using pulsed dye laser for scar treatment, and preliminary studies have shown that pulsed dye laser treats scar. In 1995, Dierickx et al. reported an average scar improvement of 77% after 1.8 laser treatments. In 1995, Dierickx et al. divided the keloid scars formed after sternotomy into two groups: a laser treatment group and a control group, and performed clinical observation, texture analysis, histology and symptom response studies. A possible etiological mechanism for the improvement of scarring by laser is suggested, namely the increase of local mast cells. Mast cells synthesize a variety of cytokines, and the presence of these factors and tissue revascularization may be related to laser stimulation of collagen remodeling and its disruption of microvessels.