When the skin is damaged, fibrous tissue (scar tissue) forms over the wound to repair and protect the injury. In some cases, scar tissue grows excessively, forming smooth, hard growths called keloids. Keloids are firm, rubber-like lesions or shiny, fibrous nodules, and can vary from pink, to red or dark brown in colour. A keloid scar is benign and not contagious, but is sometimes accompanied by severe itchiness, pain, and changes in texture. In severe cases, it can affect movement of the skin. Keloid scars are seen 15 times more frequently in highly pigmented ethnic groups than in Caucasians.
A hypertrophic scar is a cutaneous condition characterized by deposits of excessive amounts of collagen, which give rise to a raised scar, but not to the same degree as observed with keloids. Most often, like keloids, they form at the base of pimples, body piercings, cuts and burns. They often contain nerves and blood vessels. They generally develop after thermal or traumatic injury.