Keloid scar distress Keloid scar is a collective term for the appearance of morphological and histopathological changes in normal skin tissue caused by various traumatic injuries. The essence of scarring is a kind of tissue that does not have normal skin tissue structure and physiological function, and loses normal tissue vitality, abnormality and unsoundness. Clinical features include abnormal pigmentation, abnormal proliferation and dilation of blood vessels, uneven surface, decreased elasticity, increased hardness and accompanied by different degrees of atrophy. Keloid scarring brings great physical and mental pain to patients, especially after burns, scalds and severe trauma. The proliferative period of scarring for several years is almost unbearable for the patients. The subsequent atrophic phase causes the patient’s face to be completely disfigured and dysfunctional, resulting in great physical and mental dual disorders for the patient. Common types and characteristics of keloid scars Superficial keloid scars are mostly caused by damage to the superficial layers of the skin, most commonly seen in skin abrasions, superficial skin infections, superficial second-degree burns. The appearance of this kind of scar is slightly coarse and bad, sometimes with hyperpigmentation or pigment loss, but the local plane is soft, no functional obstacles, generally do not need special treatment. Linear scars are often surgical incisions, knife wounds, glass and other objects. Mostly striated, mostly flat. Atrophic keloid scars have a flat appearance, with smooth and shiny surfaces and pale hypopigmented areas, mostly on the face and back. Depressed scar: The surface of the scar is obviously lower than the surrounding normal skin and presents a depressed deformity, mostly due to the skin, subcutaneous tissue or deep tissue defects left after healing of trauma, but also due to the severe septic infection of the soft tissues of the skin caused by a wider range of tissue defects, limited to the skin and subcutaneous tissue defects, shallow depressions, and the area is small, the scar is stable, and it affects the appearance of the skin only and is not accompanied by dysfunctionality. Proliferative scarring After the skin injury heals, the scar continues to proliferate, protruding from the normal skin surface, irregular in shape, uneven in height, flushed and congested, hard and tough to the touch. Patients often have burning pain and itching sensation, and the symptoms are aggravated when the ambient temperature increases, emotional fluctuations, and eating spicy and stimulating food. The tendency to hyperplasia can continue for months to years. It occurs in deep dermal injuries and occasionally in deeper traumas and surgical incisions. Mostly due to collagen anabolism hypermetabolism, continued, more than the rate of catabolism, in a fairly long period of time, a large number of collagen fibers formation caused. Contracture scar It is named after the dysfunctional features caused. It is mainly formed by open wounds with large skin defects, through the steps of granulation, centripetal contraction of the wound margin, and epithelial regeneration to cover the scar; it can also be developed by inappropriate surgical incisions or direct suture of lacerations in certain parts of the skin with a specific direction. Keloid scars are caused by excess collagen deposits in the human skin, resulting in the formation of hyperplastic scar tissue that extends beyond the initial injury and into the normal skin. Some people call it a “benign tumor”. It is also known as a crabsfoot because it invades the surrounding area and resembles a crab’s foot. It is easily confused with hyperplastic scarring. Its nature and treatment are different from that of hyperplastic scar. The pathogenesis of keloid scars is still unclear, and therefore there is no very satisfactory treatment to date. Any single and crude intervention, such as simple surgical excision or laser resurfacing and cauterization, is very likely to cause recurrence and exacerbation. Currently, the combination of multiple therapeutic methods is considered to be the most effective and safest treatment strategy, such as surgery combined with corticosteroids, surgery combined with radiation therapy, surgery combined with compression therapy, surgery combined with silicone gel therapy, and laser combined with corticosteroids. Recently, lasers have been used more and more in scar treatment, and the application of CO2 fractional laser and pulsed dye laser (PDL) combined with tretinoin has yielded better therapeutic results. CO2 fractional laser can destroy and repair and rebuild the keloid collagen tissue through photothermal action, so that the volume of keloid can be reduced and the texture can be softened; moreover, the action of CO2 fractional laser is relatively mild and minimally invasive, which can make the collagen tissue react abnormally to aggravate the keloid and reduce the chances of recurrence. PDL, on the other hand, can cause the blood vessels within the keloid to coagulate and necrose, leading to a lack of nutrients in the keloid and preventing keloid hyperplasia; in addition, PDL can also cause a significant decrease in the expression of TGF-β1 by fibroblasts, a decrease in the fibroblast proliferative nuclear antigen PCNA, a decrease in the rate of cellular proliferation, a decrease in the deposition of collagen fibers of type Ⅲ, an increase in matrix metalloproteinase-13 activity, and an increase in the degradation of the extracellular matrix; PDL also can up-regulate ERK and p38MAP kinase activities, inducing fibroblast death. The treatment of keloid scars with CO2 fractional laser and PDL in combination with triamcinolone acetonide not only achieves better efficacy but also prevents recurrence effectively.