Scarring is a normal process. It is the end point of wound healing. It aims to seal your skin from the outside environment. Without this seal, there is the risk of infection getting in and fluid and nutrients escaping out. Quick formation of a scar was vital in terms of evolution and helping our ancestors to survive injury long enough to reproduce. However, in the modern world, an excessive amount of scar tissue can have negative consequences in terms of an ugly appearance, symptoms such as itch and pain and occasionally, it hinders surrounding joints from movement.

Collagen Molecule

A diagram of a collagen molecule

Most problem scars are described as being ‘fibroproliferative’. This means excessive amounts of tissue are formed within the skin in response to injury. Hypertrophic and keloid scars are part of this group. The connective tissue that makes up a mature scar largely consists of protein molecules and often very few cells. This accumulates in the bottom layer of the skin, called the dermis. The most abundant protein is collagen but other molecules are also produced excessively, for example chondroitin sulphate. The main cell involved in forming a scar is called a fibroblast. In hypertrophic and keloid scars, fibroblasts not only produce more scar tissue than in a normal scar, but the collagen and other molecules produced are laid down in a highly disorganised manner. Fibroblasts remodel the scar with time and the natural progression of most scars is to become less angry and more like the neighbouring skin.

Many of the other components of normal skin do not reform properly in mature scar. Excessive numbers of histamine-containing mast cells may be responsible for the itchiness of scars. Reduced numbers of oily sebaceous glands in mature scars may account for the tendency to dryness. Reduced numbers of elastic band like fibres called elastin may cause a scar to be relatively hard compared to normal skin.

Not all problem scars are fibroproliferative. If relatively little connective tissue forms, a different problem arises. The scar becomes relatively weak and stretches. These types of atrophic scars are seen with, for example, stretch marks. Some acne scarring can have elements of atrophic scarring and tethering, where the bottom of the scar becomes relatively fixed to deeper structures. Other scars can lose pigment or hairs, both of which can be cosmetically undesirable. Atrophy – or reduced tissue formation – can affect tissues other than the skin; if a scar forms normally but the tissue beneath does not reform, a depressed scar can result with a contour deformity.

In essence, a problem scar can take many forms and indeed, one scar can have several different problems across its surface or with time. This is the reason that a ‘one size fits all’ approach to treatment rarely succeeds. The treatment has to be the correct one for the scar and it may change as the scar changes with time.

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