What is a scar – and how does it form?

Scars almost always result from trauma of some kind, for example, surgery, accidents or disease.


Any damage to the outer layers of the skin (epidermis/dermis) is healed by rebuilding tissue. This tissue consists mainly of newly synthesized collagen fibers (a protein which is naturally produced by the body), which tend to be arranged in a more disorganized way and are more closely packed than the collagen fibers in uninjured skin.1 In addition, the scar tissue is less resistant to ultraviolet radiation, and permanently lacks sweat glands and hair follicles. Scarred skin areas retain up to 70% less moisture than the surrounding undamaged skin. The larger the surface area and the deeper the skin is damaged, the longer and more complicated the rebuilding process – and the greater chance that the patient will be left with a noticeable scar.

The skin healing process itself may be influenced by both intrinsic or individual factors as well as extrinsic or environmental factors including the patient’s age, skin type, chronic conditions such as diabetes and vascular conditions, wound location, hydration status, secondary infections and seasonal variation.


Normal scars and abnormal scars

A normal scar (e.g. seen as a fine line on the skin surface) usually develops during the first 48 hours after wound closure and can fade within 3 months (or longer). Various factors can interfere with the wound healing process and alter it in some way. For example, when there is an imbalance between the synthesis and degradation phases, more collagen is produced than is degraded. As a result, the scar grows in all directions, is elevated and remains hyperaemic. Such abnormal scars are classified as hypertrophic or keloid scars.2

Hypertrophic scars generally appear within 4 weeks after trauma, whereas the onset of keloids appear generally at 3 months and can be delayed up to several years after trauma.3

Abnormal scars may have the following characteristics:

  • Grow bigger
  • Remain red/dark and raised without fading
  • Cause discomfort, itching or pain
  • Restrict the movement of a joint
  • Cause distress because of appearance


1. Munroe K. Journal of Wound Care 1995; 4:143-148
2. Brissett AE, Sherris DA. Facial Plast Surg 2001; 17:263-271
3. Murray, JC. Clin Dermatol 1994; 12:27