Hypertrophic Scars and Keloids: Similarities and Differences

Hypertrophic scars and keloids both form due to excess collagen during wound healing. But hypertrophic scars stay within the confines of the wound, while keloids can grow beyond. Keloids are also much more difficult to treat.

What Are Hypertrophic Scars and Keloids?

  • Hypertrophic scars and keloids are types of scars resulting from an injury to the skin. They are more obvious than typical scars that are flat and relatively invisible. They are both the result of too much scar tissue developing near the site of a skin injury.
  • Hypertrophic scars grow right after your wound has healed and stay within the injury site. Keloids take longer to appear and can spread beyond the injury.
  • Hypertrophic scars should resolve over time with or without treatment. Keloids may remain on your body long term despite efforts to reduce them.

Keep reading to learn more about what keloids and hypertrophic scars have in common and how they differ.

What is a Hypertrophic Scar?

Hypertrophic scars are thickened scars that appear after you experience a skin injury. They may be raised or flat, and stay within the boundaries of the wound.

Hypertrophic scars occur when your body makes too much collagen while trying to repair the wound. This could be due to infection or increased tension on the wound. Collagen is thicker than your skin, which is why these scars may appear raised or feel rough.

Any of the following can trigger a hypertrophic scar to form:

  • Cuts
  • Acne
  • Insect bites
  • Burns
  • Skin infections

What is a Keloid?

Keloids are raised scar-like skin growths. Unlike hypertrophic scars, the connective tissues in keloids continue to grow beyond the wound site. While hypertrophic scars have about three times as much collagen production as is typical, keloids have about 20 times as much.

The collagen fibers also arrange themselves differently in keloids. In hypertrophic scars, the collagen fibers have a regular pattern. But in keloids, they seem to arrange themselves randomly.

Doctors consider keloids to be benign tumors on your body. This means that they are not harmful to your overall health.

Keloids may appear after a major injury to the skin or from just a minor wound. The same things that trigger a hypertrophic scar can also trigger a keloid.

According to the American Osteopathic College of Dermatology, up to 10% of people develop keloids.

Genetics may be a risk factor, per the American Academy of Dermatology, as about one-third of people with keloids have a first-degree relative (parent, sibling, or child) who develops keloids. They occur more frequently in people who have darker skin.

Both men and women can develop them at equal rates.

How to Distinguish Between Keloids and Hypertrophic Scars

At first glance, these scars may present in the same way. They may:

  • Be raised above your skin
  • Cause discomfort
  • Be itchy

Here are some differences between the two scars:

  • Hypertrophic scars:
    • Size: stay within the area of the initial wound
    • Onset: begin within a month or two after the initial wound and continue to grow for many months
    • Outlook: shrink after a year
    • Color: may be a lighter pink or red color
    • Effect on movement: can stiffen joint movement because the scar shortens tissues
    • Incidence: more common
    • Location: can develop anywhere on the body but often near sites where a wound is infected, irritated, or untreated or where a joint moves the skin
  • Keloids:
    • Size: grow beyond the initial wound
    • Onset: begin a few months or several years after the wound and grow over time
    • Outlook: do not shrink in size
    • Color: may be a darker purple-red color
    • Effect on movement: do not affect joint movement
    • Incidence: less common
    • Location: develop on certain areas of the body, including the upper torso, earlobes, and cheeks

Keloids and Hypertrophic Scars in Skin of Color

It’s important to note that according to research, there are some distinctive differences in how these hypertrophic scars and keloids develop and look on skin of color. Differences can include:

  • Hyperpigmentation
  • Scars covering wider areas
  • Scars developing over a shorter time, including reports of spontaneous development