keloid
Meaning of keloid: Healing that does not know when to stop, producing a scar that keeps spreading outward long after the injury underneath has closed.
Definition of keloid
A keloid is a thick, raised scar that grows past the edges of the injury that started it. It forms when repair fails to switch off on schedule and the skin keeps laying down collagen well after the wound has closed. Keloids feel firm and rubbery, are often darker or redder than the skin around them, and do not shrink away on their own.
Why does the scar overgrow?
Normal repair lays down collagen quickly, then spends months breaking most of it down again and reorganizing what remains into a flat scar. In a keloid the building continues while the breaking down fails to keep pace, so collagen accumulates in thick disorganized bundles that push the scar above the skin surface and outward into skin that was never injured. The cells responsible stay active and keep responding to signals that should have faded. Why this happens in some people and not others is not fully explained, but the tendency runs in families, is far more common in people with darker skin, and appears most often between adolescence and middle age.
How is it different from a hypertrophic scar?
| Feature | Keloid | Hypertrophic scar |
|---|---|---|
| Extent | Spreads beyond the original wound margin | Stays within the wound margin |
| Timing | May appear months after the injury | Usually within weeks |
| Natural course | Persists and may keep enlarging | Often flattens over a year or more |
| After surgical removal | Frequently returns, sometimes larger | Returns less often |
The two look alike at a glance, and the distinction is made by where the raised tissue sits relative to the original wound. It matters because the expected course differs, and because cutting a keloid out creates a fresh injury that can trigger a larger one in its place.
Where do they form, and what do they cause?
Any break in the skin can start one, including a piercing, an acne spot, a vaccination, a burn or a surgical incision, and some appear with no injury anyone remembers. They favor areas where skin is under tension or constant movement: the upper chest and breastbone, the shoulders and upper back, the jawline, and the earlobes, where a piercing is the usual trigger. They are not dangerous and do not turn into cancer. What they do cause is itching, tenderness, a pulling sensation, restricted movement when one crosses a joint, and distress about appearance, particularly on the face and ears. Once formed, scar tissue of this kind is stubborn, and treatment aims to flatten and soften it rather than to remove it cleanly.
Used in a sentence
The dermatology consultation was requested to evaluate a keloid that had formed at the site of an old piercing.
Good to know
A keloid that extends beyond the original wound margin is distinguished from a hypertrophic scar that stays within those margins, a distinction that affects how each is expected to behave over time.
Word origin
Where “keloid” comes from
Formed from Greek chele, meaning crab's claw, and -oid, meaning resembling, describing the claw-like extensions of the scar into surrounding skin.