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.
Like hypertrophic scars, keloid scars are thick and dark in color, but unlike hypertrophic scars, they develop beyond the boundaries of the original wound. Whereas hypertrophic scars stop growing six months after the wound, keloid scars to continue to grow for years.
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.
Keloid scars may be difficult for patients not only because of their appearance, but because they feel itchy and uncomfortable. Keloid scars can become thick enough to impinge movement, particularly if they are near a joint.
Reviewed by: Michael Fuller, MD