Why does scar tissue differ from normal skin?
- Fysiobasen
- 1 day ago
- 12 min read
A scar can remain lighter, darker, firmer, shinier, or less mobile than the skin around it. Some scars gradually become difficult to notice, while others remain broad, raised, tight, or sensitive for many years.
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The difference occurs because the body prioritises rapid and reliable wound closure over perfect reconstruction. When an injury extends into the deeper layers of the skin, the original tissue architecture is replaced by a denser collagen-based repair tissue. This scar tissue restores much of the skinās strength, but it usually lacks the organisation, elasticity, glands, hair follicles, nerves, and pigment distribution found in uninjured skin.
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The depth of the injury determines whether a scar forms
The skin consists of several layers with different structures and functions.
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The outer layer is the epidermis. Beneath it lies the dermis, which contains collagen, elastin, blood vessels, nerves, hair follicles, sweat glands, and sebaceous glands. The subcutaneous tissue lies deeper and contains fat, connective tissue, and larger blood vessels.
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The main layers can be summarised as follows:
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Skin layer | Main structures and functions |
Epidermis | Protective barrier, pigment cells, and surface renewal |
Dermis | Collagen, elastin, nerves, blood vessels, and skin appendages |
Subcutaneous tissue | Fat, insulation, cushioning, and larger vessels |
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A superficial injury limited to the epidermis can often heal without permanent scarring. Cells from the surrounding epidermis and preserved skin structures can replace the damaged area.
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When the injury reaches the dermis, the body cannot simply recreate every structure in its original arrangement. It must instead fill the defect with repair tissue.
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The deeper and wider the injury, the greater the likelihood of a visible scar.
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Wound healing begins before the scar is visible
Scar formation develops through several overlapping phases rather than one single repair event.
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The main phases are:
ā¢ Haemostasis
ā¢ Inflammation
ā¢ Proliferation
ā¢ Remodelling
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These phases overlap and influence one another throughout healing.
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Haemostasis
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Immediately after injury, blood vessels constrict and platelets gather in the damaged area. A clot forms to limit bleeding and create a temporary scaffold for repair cells.
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Inflammation
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Immune cells enter the wound and remove bacteria, damaged cells, and tissue debris. They also release signalling molecules that recruit fibroblasts, blood-vessel-forming cells, and new skin cells.
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Proliferation
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Fibroblasts produce collagen and other extracellular material. New blood vessels grow into the wound, skin cells move across the surface, and myofibroblasts begin pulling the wound edges closer together.
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Remodelling
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The repair tissue is reorganised over months or years. Collagen is broken down and rebuilt, the number of blood vessels decreases, and the scar usually becomes flatter, paler, and stronger.
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A wound may look closed after a few weeks while the underlying scar remains biologically active for a long time.
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Scar collagen is arranged differently
Normal dermis contains a complex, interwoven network of collagen fibres extending in several directions.
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This organisation helps healthy skin tolerate pulling, twisting, stretching, and compression from different angles.
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In scar tissue, collagen is deposited more rapidly and often in a more parallel and densely packed arrangement. The immediate priority is to close the wound and restore mechanical stability.
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The main differences can be summarised as follows:
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Normal skin | Scar tissue |
Interwoven collagen network | More parallel collagen arrangement |
Greater elasticity | Usually stiffer |
Normal hair follicles and glands | Often fewer or absent |
Even pigment distribution | May be lighter or darker |
Normal nerve organisation | May be numb or hypersensitive |
Normal skin movement | May adhere to deeper tissue |
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Early repair tissue contains relatively more collagen type III.
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During remodelling, much of this is replaced by stronger collagen type I. The fibres become thicker and develop more cross-links.
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The remodelling process improves tissue quality but rarely recreates the original skin architecture completely.
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A mature scar does not regain full skin strength
A newly closed wound has limited tensile strength. It may look intact on the surface while still being vulnerable to pulling and repeated loading.
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Strength increases as:
ā¢ Collagen fibres become thicker
ā¢ Cross-links develop between fibres
ā¢ Excess collagen is removed
ā¢ Fibres align with mechanical stress
ā¢ The repair tissue becomes more organised
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Even after full maturation, scar tissue usually reaches only around 70ā80 percent of the tensile strength of uninjured skin.
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The exact value varies with the injury, body location, healing conditions, age, infection, circulation, and other individual factors.
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Most mature scars tolerate ordinary daily activity well. The reduced strength is more relevant during very high loading, repeated trauma, or further surgery in the same area.
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Hair follicles and glands are often lost
Hair follicles, sweat glands, and sebaceous glands are located mainly in the dermis.
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If these structures are destroyed by a deep injury, they are usually not rebuilt within the scar.
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A deep scar may therefore:
ā¢ Lack hair growth
ā¢ Produce less sweat
ā¢ Produce less skin oil
ā¢ Become dry more easily
ā¢ Respond differently to heat and cold
ā¢ Have reduced local temperature regulation
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This is one of the main reasons scar tissue looks and behaves differently from the surrounding skin.
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After extensive burns, the loss of sweat glands can reduce the bodyās ability to cool the affected area.
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The absence of sebaceous glands may also make the scar drier and more vulnerable to irritation.
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New scars contain many blood vessels
Fresh scars often appear red, pink, or purple because the repair tissue contains many small blood vessels.
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These vessels supply oxygen, nutrients, immune cells, and building materials to the healing wound.
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A new scar may therefore be:
ā¢ Red
ā¢ Warm
ā¢ Slightly swollen
ā¢ More visible after activity
ā¢ More sensitive to heat
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As healing progresses, the demand for blood supply decreases. Many of the newly formed vessels disappear, and the scar gradually becomes paler.
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This process may take many months.
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Some scars remain red for more than a year, particularly if they are raised, irritated, exposed to tension, or still undergoing active remodelling.
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Increasing redness combined with warmth, pain, swelling, or discharge may indicate infection or another complication rather than normal maturation.
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Pigment does not always return evenly
Skin colour is largely determined by melanin produced by melanocytes in the epidermis.
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An injury can damage these cells or alter how pigment is produced and distributed during healing.
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The scar may become:
ā¢ Lighter than the surrounding skin
ā¢ Darker than the surrounding skin
ā¢ Unevenly pigmented
ā¢ More visible after sun exposure
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Darker post-inflammatory pigmentation is more common in people with more deeply pigmented skin.
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Pale scars may occur when melanocytes are destroyed or fail to repopulate the healed area.
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Immature scars may also react differently to ultraviolet radiation. Sun exposure can darken the scar or increase the contrast between the scar and nearby skin.
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Consistent sun protection is therefore particularly relevant during the first year after injury or surgery.
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Myofibroblasts pull the wound together
Some fibroblasts develop into myofibroblasts during healing.
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These cells have contractile properties and help reduce the size of the wound by pulling its edges towards one another.
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This is useful during normal repair, but excessive contraction can make a scar tight and restrictive.
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A contracting scar may cause:
ā¢ Tightness
ā¢ Pulling during movement
ā¢ Reduced skin mobility
ā¢ Limited joint range
ā¢ Pain or discomfort
ā¢ Changes in posture or movement
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Scars crossing joints, finger creases, the neck, or other highly mobile areas can have a greater functional effect than scars in less mobile regions.
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Large burn scars are particularly prone to contractures because extensive areas of skin may shorten during healing.
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Scar tissue can attach to deeper structures
Normal skin glides over the tissue beneath it.
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After surgery or deep injury, collagen may form connections between the skin, fascia, muscle, tendon, or other underlying structures.
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These adhesions can reduce normal tissue movement.
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A person may notice:
ā¢ Pulling during movement
ā¢ Reduced skin glide
ā¢ A firm or tethered feeling
ā¢ Discomfort when stretching
ā¢ Limited movement near a joint
ā¢ Altered movement patterns
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Not all scars become significantly adherent.
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The effect depends on the depth of the injury, location, surgery, inflammation, movement during healing, and individual scar response.
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When a scar restricts function, rehabilitation may include graded movement, stretching, strengthening, desensitisation, and manual techniques.
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Why do scars itch?
Itching is very common during wound healing.
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Several mechanisms may contribute:
ā¢ New nerve fibres growing into the area
ā¢ Dry skin
ā¢ Inflammatory chemicals activating itch receptors
ā¢ Tight or contracting tissue
ā¢ Friction from clothing
ā¢ Ongoing activity in the healing tissue
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Mild itching is often part of normal scar maturation.
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The sensation may be particularly strong in hypertrophic scars and burn scars.
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Scratching can damage fragile skin, increase inflammation, and create new wounds.
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Moisturiser, cooling, pressure, silicone products, or medical treatment may be useful when itching is severe.
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Increasing itch accompanied by rash, marked redness, discharge, or swelling may instead indicate contact allergy, irritation, or infection.
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Nerve recovery is slow and unpredictable
Deep injuries and surgical incisions can cut, stretch, or irritate small sensory nerves.
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As the nerves recover, fibres grow slowly and may not return in the same arrangement as before.
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A scar can therefore feel:
ā¢ Numb
ā¢ Tingling
ā¢ Burning
ā¢ Tender
ā¢ Electric
ā¢ Hypersensitive to touch
ā¢ Less sensitive to heat or cold
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Sensation may continue changing for months or years.
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Some areas regain nearly normal feeling, while others remain partly numb.
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In some cases, nerve fibres form a painful neuroma or become trapped in scar tissue.
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This is more likely after amputations, larger nerve injuries, or surgery involving a major nerve branch.
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Persistent burning, electric pain, severe hypersensitivity, or weakness may require further assessment.
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Mechanical tension influences scar width
The forces acting across a healing wound affect how the scar develops.
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A wound exposed to repeated stretching or pulling may gradually become wider.
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Areas commonly exposed to high tension include:
ā¢ Shoulders
ā¢ Chest
ā¢ Upper back
ā¢ Knees
ā¢ Elbows
ā¢ Skin across joints
ā¢ Areas repeatedly stretched during movement
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Surgeons often try to place incisions along natural skin-tension lines when possible.
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This may reduce pulling across the wound and improve the final scar.
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Cosmetic placement is not always the main priority. Access to deeper structures, safety, and surgical technique may require a different incision direction.
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Movement must also be balanced carefully.
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Too much tension too early may widen or reopen the wound, while prolonged immobilisation can contribute to stiffness and adhesions.
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Hypertrophic scars stay within the original wound
A hypertrophic scar is raised and thickened but remains within the boundaries of the original injury.
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It develops when collagen production remains high and remodelling does not adequately reduce the excess tissue.
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Hypertrophic scars may be:
ā¢ Red or purple
ā¢ Firm
ā¢ Raised
ā¢ Itchy
ā¢ Painful
ā¢ Less mobile
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They are more common after:
ā¢ Burns
ā¢ Infected wounds
ā¢ Slow wound closure
ā¢ Deep injuries
ā¢ Wounds exposed to high tension
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Hypertrophic scars may gradually flatten and become less active over time.
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Maturation can still take several years, and treatment may be needed when the scar causes pain, severe itching, functional limitation, or significant distress.
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Keloids grow beyond the original injury
A keloid extends outside the boundaries of the original wound.
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The scar tissue may continue to grow even after the initial injury has healed.
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Keloids occur more frequently in people with darker skin and in families with a genetic tendency.
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They often develop on:
ā¢ Earlobes
ā¢ Shoulders
ā¢ Upper arms
ā¢ Chest
ā¢ Neck
ā¢ Upper back
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The main differences between hypertrophic scars and keloids are:
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Hypertrophic scar | Keloid |
Remains within the wound | Grows beyond the wound |
May gradually become smaller | May continue to enlarge |
Often appears relatively soon | May develop over a longer period |
Strongly linked to tension and healing | More strongly influenced by genetics |
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Keloids are benign and do not become cancerous.
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They can still cause itching, pain, tightness, and significant cosmetic or psychological distress.
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Surgical removal alone has a high recurrence rate, so treatment is often combined with injections, silicone, pressure, cryotherapy, laser, or other approaches.
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Why some people scar more strongly
Scar development differs considerably between individuals.
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Important factors include:
ā¢ Genetics
ā¢ Skin pigmentation
ā¢ Age
ā¢ Injury depth
ā¢ Wound size
ā¢ Body location
ā¢ Mechanical tension
ā¢ Infection
ā¢ Healing time
ā¢ Blood supply
ā¢ Smoking
ā¢ Nutrition
ā¢ Diabetes and other medical conditions
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Younger people may develop more active hypertrophic scars because collagen production and fibroblast activity are often stronger.
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Wounds that heal quickly and without infection generally produce less scarring than wounds that remain open for long periods.
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Smoking and impaired circulation can delay healing by reducing oxygen delivery to the tissue.
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Poorly controlled diabetes may also increase the risk of delayed healing and infection.
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A closed wound is not a mature scar
The skin surface may close in days or weeks, but scar remodelling continues much longer.
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The maturation phase may last from several months to more than two years.
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During this time, the scar may gradually become:
ā¢ Flatter
ā¢ Paler
ā¢ Softer
ā¢ Less itchy
ā¢ Less tender
ā¢ More mobile
ā¢ Stronger
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The changes are not always steady.
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A scar may temporarily become redder after exercise, heat, friction, or stretching.
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It is therefore usually too early to judge the final appearance after only a few weeks or months.
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A scar that looks prominent after three months may be substantially less visible after one or two years.
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Massage may improve symptoms and mobility
Scar massage is commonly used after surgery, burns, and deep skin injuries.
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Possible aims include:
ā¢ Improving skin glide
ā¢ Reducing sensitivity
ā¢ Increasing tolerance to touch
ā¢ Managing swelling
ā¢ Reducing the feeling of tightness
ā¢ Supporting movement
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Massage does not simply break up or remove collagen.
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The tissue cannot be manually erased.
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The benefit may instead come from graded mechanical input, improved movement between tissue layers, desensitisation, and increased confidence in using the area.
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Evidence for scar massage is mixed, and the response varies between scar types.
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Massage should not be performed over an open wound, a fresh wound separation, active infection, or tissue that has not been cleared for loading.
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Silicone may help raised scars
Silicone gel and silicone sheets are widely used for hypertrophic scars and keloid-prone skin.
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The exact mechanism is not fully established.
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Silicone may affect:
ā¢ Hydration of the outer skin layer
ā¢ Fibroblast activity
ā¢ Collagen production
ā¢ Itching
ā¢ Redness
ā¢ Scar thickness
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Treatment usually begins only after the wound has completely closed.
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Consistent use over several weeks or months is often necessary.
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Silicone does not remove the scar completely, but it may help make the tissue flatter, softer, or less symptomatic.
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Skin irritation can occur, especially if sweat and moisture collect beneath the material.
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Pressure treatment is often used after burns
Compression garments and pressure dressings are commonly used for large hypertrophic scars following burns.
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The pressure may influence blood flow, collagen organisation, and cellular activity within the scar.
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Treatment often requires wearing the garment for much of the day over many months.
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Compression garments may feel:
ā¢ Hot
ā¢ Tight
ā¢ Itchy
ā¢ Difficult to put on
ā¢ Highly visible
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The fit must be monitored carefully.
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Too much pressure can cause pain, skin injury, numbness, or impaired circulation.
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Too little pressure may provide limited benefit.
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This form of treatment is usually managed by a specialised burn or rehabilitation team.
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Other treatments depend on the scar type
Several medical and surgical treatments may be considered for painful, raised, restrictive, or cosmetically distressing scars.
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Options include:
ā¢ Corticosteroid injections
ā¢ Laser treatment
ā¢ Cryotherapy
ā¢ Surgical revision
ā¢ Silicone products
ā¢ Compression
ā¢ Radiotherapy for selected keloids
ā¢ Skin grafting
ā¢ Physiotherapy or occupational therapy
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Corticosteroid injections can reduce fibroblast activity and flatten raised scars.
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Possible side effects include skin thinning, pigment changes, and visible blood vessels.
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Laser treatment may target redness, pigmentation, thickness, or surface texture.
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Several sessions are often required.
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Surgical revision can change the direction, width, or position of a scar, but it creates a new wound and cannot guarantee a less visible result.
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Sun protection reduces colour contrast
An immature scar is particularly sensitive to ultraviolet radiation.
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Sun exposure can darken the scar or make pigment differences more permanent.
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Practical measures include:
ā¢ Covering the scar with clothing
ā¢ Using high-factor sunscreen
ā¢ Reapplying sunscreen regularly
ā¢ Avoiding intense sun exposure
ā¢ Continuing protection throughout the first year
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Sun protection does not remove the scar.
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It can reduce the risk that the scar becomes noticeably darker than the surrounding skin.
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This is particularly relevant for people who develop strong post-inflammatory pigmentation.
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Movement matters when a scar crosses a joint
Scars located over joints may restrict function if they contract or adhere to underlying tissue.
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Gradual movement helps preserve:
ā¢ Joint range of motion
ā¢ Skin glide
ā¢ Muscle strength
ā¢ Normal movement patterns
ā¢ Tolerance to stretch
ā¢ Daily function
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After surgery, movement must follow the restrictions associated with tissue healing.
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Aggressive stretching too early can increase wound tension or disrupt the repair.
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Too little movement over time may contribute to stiffness, weakness, and contracture.
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A physiotherapist or occupational therapist may use exercise, positioning, splinting, compression, and graded scar mobilisation when function is affected.
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When a scar should be assessed
Most scars mature normally and do not require medical treatment.
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Assessment may be appropriate if the scar:
ā¢ Becomes progressively thicker
ā¢ Grows beyond the original wound
ā¢ Restricts movement
ā¢ Causes persistent severe pain
ā¢ Produces intense itching
ā¢ Reopens repeatedly
ā¢ Becomes warm, red, or discharging
ā¢ Changes colour or shape suddenly
ā¢ Develops a rapidly growing lump
ā¢ Causes marked numbness or electric pain
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Redness, warmth, increasing pain, pus, or fever may indicate infection and should be assessed promptly.
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An old scar that develops a persistent ulcer or a new growth should also be examined.
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Malignant change within scars is rare, but a non-healing wound should not be ignored.
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Summary
Scar tissue differs from normal skin because the body repairs deep injuries with a rapidly produced collagen network rather than rebuilding the skinās original architecture. The collagen is more densely and parallelly arranged, making the tissue stiffer and less elastic. Deep scars often lack hair follicles, sweat glands, sebaceous glands, and normal nerve organisation. They may therefore appear lighter or darker, feel numb or hypersensitive, and move less freely than surrounding skin. Scars continue to mature for months or years, and many gradually become flatter, softer, and paler. Raised, growing, painful, or function-limiting scars may benefit from silicone, compression, injections, laser, surgery, or adapted rehabilitation.
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Sources
ā¢ Gurtner GC, Werner S, Barrandon Y, Longaker MT. Wound repair and regeneration.Ā Nature. 2008;453(7193):314ā321.
ā¢ Rodrigues M, Kosaric N, Bonham CA, Gurtner GC. Wound healing: A cellular perspective.Ā Physiological Reviews. 2019;99(1):665ā706.
ā¢ Ogawa R. Keloid and hypertrophic scars are the result of chronic inflammation in the reticular dermis.Ā International Journal of Molecular Sciences. 2017;18(3):606.
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