There are many factors that influence the formation of keloids, which can be summarized into two aspects: self-factors and external factors. Self-factors include: (1) Race: Keloids and keloid scars occur in all races, but have a high incidence in people of color. (2) Age: Fetal trauma generally heals without scarring and keloids occurring. Young people have a higher incidence of scarring and keloids after trauma healing than older people, and the thickness of scarring and keloid hyperplasia at the same site is thicker in young people than in older people. This may be related to the fetal tissue injury repair process acute inflammatory stage is not obvious, fibroblast formation is less, collagen deposition is not much, young people’s tissue growth is vigorous, the reaction to trauma is stronger, and young people’s skin tension is greater than that of the elderly and other factors. According to statistics, the incidence of scarring is the highest among people aged 10-20 years old, accounting for 64.4%. (3) Skin pigmentation: skin pigmentation has a close relationship with the occurrence of keloid. For example, keloid often occurs in the parts of the human body where the pigment is more concentrated, and rarely occurs in the palms of the hands or soles of the feet, which contain less pigment. (4) General condition: such as malnutrition, anemia, vitamin deficiency, imbalance of micronutrient balance, diabetes and other systemic factors, are not conducive to wound healing, so that the wound healing time is prolonged, which is conducive to the occurrence of keloid scars. (5) Individual constitution: keloid often occurs in family, and keloid occurs in different parts of the same person at different times are keloid, which indicates that the occurrence of keloid may be related to individual constitution. (6) Metabolic state: keloid scars and keloid scars occur more often in adolescents and pregnant women, which may be associated with their vigorous metabolism, pituitary function, estrogen, melanocyte stimulating hormone, thyroxine and other hormones secreted exuberantly. (7) Site: Any injury to the body deep into the reticular layer of the skin can form a scar. However, the occurrence of keloid and keloid in different parts of the same body is different, some parts of the formation of keloid is less obvious, such as hands and feet, eyelids, forehead, lower back, external genitalia, etc. keloid and keloid incidence is low; some parts such as jaw, chest, deltoid muscle, upper back, elbows, hips, knees, ankles and dorsum of the foot and other parts of the body is easy to occurrence of keloid and keloid. This may be related to the fact that different parts of the body have different skin tensions and different amounts of activity, and that greater skin tensions and more activity increase the likelihood of scarring and keloids. (8) Influence of skin tension line: In 1973, Borges drew a detailed skin line and tension line, or langer’s line, based on previous history and practical observation. The incision or wound parallel to the line, the edge of the wound is subjected to less tension, the wound healing scar is smaller, and vice versa, the scar is larger. Clinically, according to the direction of this line, “Z” plastic surgery can be done to change the tension of the scar and reduce the recurrence of scarring. External factors include: ① Wound and surgical incision: surgical incision is made perpendicular to the skin surface, and the scar is the thinnest after healing; the greater the inclination of the blade on the surface of the skin during the incision, the wider the dermal scar will be, and the scar will be more and more thick and obvious after healing. ② Infection: scarring is easy to occur after wound infection. Because of the wound infection, inflammatory cell infiltration, bacterial toxins can inhibit the migration and proliferation of epithelial cells, tissue proteins and polysaccharides of the dermis are consumed, myofibroblasts and fibroblasts increase rapidly, excessive proliferation of granulation tissue, easy to form proliferative scarring and keloid tissue. In general, the longer the infection, the more serious the degree of scar formation, infected wounds without adequate drainage and removal of necrotic tissue, the wound is difficult to heal, even if it can be healed, the healing will form a serious scar. Foreign body on the wound: if there is dust, talcum powder, cotton fibers, thread knots, foreign drugs containing slag, etc. on the wound, it can stimulate the proliferation of scar tissue and cause scar hyperplasia. Hematoma on the wound surface: Hematoma on the wound surface creates conditions for infection, adversely affects wound healing, and is conducive to the proliferation of scar and keloid. ⑤ Depth of injury: if the injury plane only touches the superficial layer of dermis, the wound will be light red after healing, and will subside in about 3 months without scarring; if the injury plane reaches the reticular layer of dermis, the wound will produce scarring after healing. (6) Time of wound repair: the earlier the wound heals, the lower the incidence of scarring, otherwise the incidence of scarring increases. (7) The method of wound repair: when the wound is small, direct suture to align the wound edge is good. When the wound is large, flap repair is more effective than skin grafting. If it is allowed to heal on its own, there must be scarring; with autologous or allogeneic cultured epidermal cells transplanted in Ⅲ burn wounds, due to the lack of dermis, the wound tends to scarring; if given to the fracture of the skin piece grafting, the contraction of the trauma is alleviated, myofibroblasts are reduced, and keloid scarring is reduced; if given to the full-thickness skin grafting, the contraction of the trauma is minimized, myofibroblasts are most rapidly regressed, and keloid scarring is most insignificant, which is the most important way to prevent This is an effective measure to prevent scar proliferation and scar contracture. (8) chronic stimulation: wound scarring can be due to friction, scratching, sun exposure and other chronic stimulation and proliferation. The effect of treatment: treatment errors can cause keloid hyperplasia and keloid, such as improper bandaging and fixation, delayed implantation, and failure to carry out appropriate functional exercise and rehabilitation after wound healing. Research on cell growth factors has become the mainstay of healing wounds, and studies have shown that a variety of growth factors are related to the occurrence, development and regression of keloid scars and keloid scars; therefore, active and in-depth research on cytokines will make it possible to explore new ways of healing keloid scars.