It is a result of an overgrowth of granulation tissue (collagen type III) at the site of a healed skin injury which is then slowly replaced by collagen type I. Keloids are firm, rubbery lesions or shiny, fibrous nodules, and can vary from pink to the color of the person's skin or red to dark brown in color.

Collagen, used in wound repair, tends to overgrow in this area, sometimes producing a lump many times larger than that of the original scar.

Studies have shown that those with darker complexions are at a higher risk of keloid scarring as a result of skin trauma.

However, no single gene has yet been identified which is a causing factor in keloid scarring but several susceptibility loci have been discovered, most notably in Chromosome 15.

Case series have reported clinically severe forms of keloids in individuals with a positive family history and black African ethnic origin.

Histologically, keloids are fibrotic tumors characterized by a collection of atypical fibroblasts with excessive deposition of extracellular matrix components, especially collagen, fibronectin, elastin, and proteoglycans.

Generally, they contain relatively acellular centers and thick, abundant collagen bundles that form nodules in the deep dermal portion of the lesion.

Keloids present a therapeutic challenge that must be addressed, as these lesions can cause significant pain, pruritus (itching), and physical disfigurement.

Treatments (both preventive and therapeutic) available are pressure therapy, silicone gel sheeting, intra-lesional triamcinolone acetonide (TAC), cryosurgery (freezing), radiation, laser therapy (pulsed dye laser), interferon (IFN), fluorouracil (5-FU) and surgical excision as well as a multitude of extracts and topical agents.

[13] Appropriate treatment of a keloid scar is age-dependent: radiotherapy, anti-metabolites and corticosteroids would not be recommended to be used in children, in order to avoid harmful side effects, like growth abnormalities.

The mechanism of how exactly pressure therapy works is unknown at present, but many patients with keloid scars and lesions have benefited from it.

[7] Intralesional injection with a corticosteroid such as triamcinolone acetonide (Kenalog) does appear to aid in the reduction of fibroblast activity, inflammation and pruritus.

The authors only found two small studies (36 participants in total) that compared these treatment options so were unable to determine which (if any) was more effective.

Persons with razor bumps are advised to stop shaving in order for the skin to repair itself before undertaking any form of hair removal.

[21] Keloids can tend to appear to grow over time without even piercing the skin, almost acting out a slow tumorous growth; the reason for this tendency is unknown.

Extensive burns, either thermal or radiological, can lead to unusually large keloids; these are especially common in firebombing casualties, and were a signature effect of the atomic bombings of Hiroshima and Nagasaki.

[24] The famous American Civil War-era photograph "Whipped Peter" depicts an escaped former slave with extensive keloid scarring as a result of numerous brutal beatings from his former overseer.