The incidence of new scarring per year in the developed world is estimated to be at least 100 million; a large percentage will be affected by abnormal scarring, which can be categorized mainly as hypertrophic scars and keloids. There is also good evidence to suggest that atrophic scars and striae distensae (or stretch marks) are categories of abnormal scarring.

Abnormal Scar Types

Hypertrophic Scars

Hypertrophic Scars are typically raised, red or pink and sometimes itchy but do not exceed the margins of the original wound. Hypertrophic scars usually subside with time. Histologically, hypertrophic scars have flatter type III collagen bundles, with fibers arranged in a wavy pattern, but predominately oriented parallel to the epithelial surface.

Collagen synthesis is 6 times as great as in normal unscarred skin and the ratio of type I to type II collagen is also higher. Hypertrophic scars also have nodular structures of alpha-smooth muscle actin, which expresses myofibroblasts, small vessels and fine collagen fibers.


Keloids on the other hand range in consistency from soft and doughy to hard and rubbery. They do not infiltrate into the surrounding normal tissue and continue to evolve over time with no regress phase. Histologically, collagen bundles are not present but instead the collagen type I and type III fibers lie in a haphazardly connected loose sheet randomly orientated to the epithelial surface. In addition, the collagen synthesis is approximately 20 times greater as that in normal unscarred skin and the ratio of type I to type II collagen is also higher. Keloids  also have an overproduction of the growth factors TGF-B and PDGF produced by fibroblast proteins.

In comparison to the above two abnormal histological feature, normal skin contains collagen bundles running parallel to the epithelial surface.

In 2002, an International Advisory Panel on Scar Management published Clinical Recommendations on Scar Management, based on a qualitative overview of 300 published references and expert consensus on best practices. Silicone was recommended as first line therapy for prevention of scarring and first line treatment for the initial management of scarring, in addition to the recommended management modality with adjunct therapies for secondary management.


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