What is scar tissue?

Scars represent the visible consequences of trauma and have different properties to healthy skin; as such, care of scarred skin should be very specific but have an emphasis on hydration, as Dr Katerina Steventon explains

Cosmetics Business asks: what is scar tissue and how should it be looked after?

Over to the expert…

Scars represent the visible consequences of trauma, injury, burns, surgery, abrasion, or acne and striae distensae. The skin as a whole, but in particular the very top layer of the epidermis – the stratum corneum – forms a barrier protecting our body. This barrier prevents water loss, bacterial ingress and sunlight-induced inflammation.

The integrity of the stratum corneum layer is essential; epidermal keratinocytes are tightly adhered to each other by cellular junctions, and extracellular lipids are packed in ideal arrangements to regulate trans-epidermal water loss (TEWL).

The dermis is filled with extracellular matrix and structural proteins, ie collagen, responsible for tensile force in the skin.

In the event of an injury, when the skin is cut, burnt or abraded, the body makes an attempt to close the skin fast. The speed of the repair happens at the expense of the quality, resulting in scar tissue.

Newly formed scar tissue has a stratum corneum that is dysfunctional, with a weak barrier leading to dramatic increases in water loss, skin dryness and changes in the biomechanical properties of the newly formed tissue. The scars have a reduced barrier function compared with healthy skin and the integrity of the barrier improves only with scar maturation.

Scars also have an increased number of fibroblasts in the dermis, with a change in fibroblast phenotype and collagen orientation. Rising keloid and hypertrophic scars are a result of the over-production of collagen by fibroblasts during wound healing.

These scars are associated with changes of intrinsic cellular mechanical properties: it is the stiffness of the tissue that determines the regenerative ability during wound healing.

Scars are visible and hard to live with.

Newly formed scar tissue has a stratum corneum that is dysfunctional, with a weak barrier leading to dramatic increases in water loss

People with scars often report decreased quality of life. They present functional and psychological issues, and the management of scars can be slow and difficult. Scars induce distress because of their aesthetically unpleasant appearance, especially if they look excessively raised, large or erythematous, or feel painful, tight or itchy.

Hydration is essential in scar management. Dehydrated scars are often pruritic and painful due to the impaired epidermal structure. Hydration regulates cytokine production, which helps to reduce hypertrophic scarring.

Beyond hydration, there is a range of treatments and technologies with evidence to support their use: physical topical technologies (silicone gel sheets, other silicone products); physical devices (laser and radio therapy, pressure therapy and dermabrasion); medication; and topical personal care products (plant extracts and oils rich in oleic and linoleic acids, and hydrophobic cosmetics rich in silicones and mineral oils).

In terms of timing, a typical scar maturation takes 18-24 months, with the scar slowly flattening and fading. When considering a therapy that will have the greatest impact on a scar, it is important to be respectful of the scar type in conjunction with the treatment timeline.

Some therapies are to be used continuously (eg silicone gel sheets and topical skin care), and some are most effective in the early stages (corticosteriod injections after wound closure; dermabrasion eight weeks after surgery). Regardless of treatment protocol, the surgical revision of scars, if necessary, should be delayed for at least 12 months.

When people consider scar therapies, they need to understand what they are trying to achieve, be it prevention in people who are prone to scarring, or a treatment focusing on reduction in scar thickness, or itching, redness and dryness.

The efficacy of scar therapies is prone to bias, yet qualitative research questionnaires, eg Observer Scar Assessment Scale (OSAS) or self-assessed Patient Scar Assessment Scale (PSAS), have to be considered.

In a recent study, it was reported that a plant oil-based product had the highest agreement on statements about skin feel – eg provides a long lasting, soft and supple skin feeling – caring effect and quick absorption. The statements associated with improving the scar or striae appearance were secondary.

Although scars can never be completely eliminated in adult skin, focus on skin feel and functionality rather than purely on the scar’s physical appearance might be more beneficial. The skin is our largest sensory organ after all.

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