Scars are the result of the healing process that the skin undergoes when it attempts to repair a wound. Every kind of injury to the skin has the potential to cause scarring. Scars vary in shape, color and composition. Some scars are pale and flat, while others are dark in color and appear raised. Keloid scars are raised, and appear red or dark in color.
When a wound damages the skin, the type of scarring depends on the extent of the injury. Superficial injury only affects the outermost layer of skin, called the epidermis, and such injury results in minimal scarring. If the injury penetrates deeper than the epidermis, to the underlying dermis, the damage is more severe, and the scarring is more pervasive.
Tissue beneath the epidermis heals by forming collagen fibers. After sustaining a wound, cells in the wound bed called fibroblasts produce a protein called collagen that fills and closes the wound bed and forms a scar.
Development of keloid scars is an inherited trait, so certain people develop keloids while others do not. Keloid scars appear more frequently in young people and people with dark skin, although that does not diminish their appearance in older people, and people of all skin types. Keloid scars appear most frequently on the shoulders, back and chest.