Keloids usually occur at the site of skin damage (e.g., acne, burns, chicken pox, cuts, insect bites, piercings, surgery, tattoos, vaccinations), although they can also occur spontaneously. Whether or not a keloid will form is not determined by the severity of the wound - even a minor skin abrasion can result in keloid formation.
Keloids are the result of abnormal wound healing. Normally, there is a balance between the production and the breakdown of collagen, which is a protein that makes up the fibres in the skin. With keloidal scars, the cells in the skin called fibroblasts produce excessive amounts of collagen. The collagen fibres are also thicker and wavier. This leads to the thick, raised appearance that is characteristic of keloidal scars. It is unclear what prompts this unusual healing process. Possible causes include genetic factors, skin tension, skin color (they are more common in those with darker skin tones), and the presence of a very high number of fibroblasts in the skin.
Keloids are usually firm, raised, shiny, and smooth. They are often pink or red, or much darker or lighter in color than the surrounding skin. Keloids always extend beyond the limits of the original wound, sometimes by many centimetres. The color, shape, and size of the scars may change with time. They are often very itchy and associated with shooting pains.
Keloids are more likely to develop on the arms, back, ears, lower legs, mid-chest, and neck. They may form as a wound heals, or they may take several months or even years to develop.
Depending on their appearance and location, they can cause some psychological distress, as keloids can be quite prominent. Keloids can also interfere with movement, especially if they are on a joint.
Keloids are different from hypertrophic (abnormally thickened) scars in that they extend beyond the edges of the site of injury and can occur without any inciting injury.
Keloids can be diagnosed by your doctor or dermatologist (skin specialist). Diagnosis is based on the location and appearance of the scar, and how it progresses over time. Your doctor may do a physical exam and look at your medical and personal history to rule out any other possible diseases or conditions.
