Keloids and Hypertrophic Scars

What is it?

Keloids and hypertrophic scars are types of abnormal (pathological) scarring in which the skin produces too much collagen — the structural protein that gives skin its strength — during the wound-healing process. Instead of forming a flat, fading scar, the skin creates a raised, thickened, often firm mass of scar tissue.

The key difference between the two:

• Hypertrophic scars stay within the boundaries of the original wound. They are raised and firm but tend to improve on their own over months to years
• Keloids grow beyond the edges of the original wound, invading surrounding normal skin. They do not regress spontaneously and may continue to enlarge over time

Both can develop after any form of skin injury — surgery, burns, acne, piercings, vaccinations, or even minor scratches — though keloids can occasionally appear without a clear triggering injury.

Who is affected?

Keloids and hypertrophic scars can affect anyone, but certain groups are at considerably higher risk.

• Prevalence: Hypertrophic scars develop in up to 70% of burn patients and after 40–70% of surgical procedures. Keloids affect an estimated 6–16% of people of African descent
• Ethnicity: People with darker skin (Fitzpatrick skin types IV–VI) — particularly those of African, Asian, and Hispanic ancestry — are significantly more prone to keloid formation
• Age: Most common between 10 and 30 years of age; rare in the very young and elderly
• Family history: A strong genetic component exists — having a first-degree relative with keloids substantially increases your risk
• Body sites: Certain areas are particularly prone: earlobes, shoulders, upper chest (sternum), upper back, and the jawline. Conversely, the eyelids, palms, soles, and genitalia are rarely affected
• Triggers: Ear piercings, acne, surgical incisions, burns, and vaccinations are among the most common causes. Even minor injuries can trigger keloids in susceptible individuals

What causes it?

The exact mechanism is not fully understood, but the central problem is a prolonged and excessive inflammatory response in the deep layer of the skin (reticular dermis) during wound healing.

• Excessive collagen production: Fibroblasts (the cells responsible for producing collagen) become overactive, producing dense, disorganized collagen fibres rather than the orderly, parallel arrangement found in normal scars
• Chronic inflammation: Pro-inflammatory signals — particularly TGF-β (transforming growth factor beta) — remain elevated far longer than in normal wound healing, driving continuous fibroblast activation
• Genetic predisposition: Multiple gene variants have been identified; the condition runs strongly in families, with autosomal dominant inheritance patterns in some. People of African and Asian ancestry carry higher genetic susceptibility
• Mechanical tension: Scars over areas of high skin tension (chest, shoulders, joints) are more prone to pathological scarring. Mechanical forces stimulate fibroblast activity through mechanotransduction pathways
• Melanin: Recent research suggests that increased melanin production may promote fibroblast proliferation, which may partly explain the higher incidence in darker-skinned individuals

What are the clinical features?

The appearance and symptoms differ between the two types.

Hypertrophic scars:

• Raised, firm, often red or pink scar that stays within the wound boundaries
• Usually develops within weeks of the injury
• May feel tight or restrictive, especially over joints (scar contracture)
• Tends to flatten and soften gradually over 1–2 years
• Itching is common, particularly during the maturation phase

Keloids:

• Firm, rubbery, shiny nodule or plaque that extends beyond the original wound margins
• Colour varies: pink, red, or dark brown/purple, often darker than the surrounding skin
• May develop months or even years after the initial injury
• Does not regress spontaneously — may continue to grow slowly over years
• Frequently itchy, painful, or tender; some patients describe a burning or stinging sensation
• Surface may be smooth or irregular; claw-like projections can develop at the edges
• Can be cosmetically disfiguring and functionally limiting (restriction of movement near joints)

Psychosocial impact: Keloids and hypertrophic scars — particularly those on visible areas such as the face, neck, or chest — can cause significant emotional distress. Patients commonly report embarrassment, reduced self-confidence, anxiety about their appearance, and avoidance of social situations. This psychological burden should not be underestimated.

How is it diagnosed?

Diagnosis is clinical — based on the appearance and history of the scar.

• Clinical examination: A firm, raised scar that extends beyond the wound margins (keloid) or stays within them (hypertrophic scar). Location, time course, and relationship to the original wound are key diagnostic features
• Patient history: Previous scarring behaviour, family history, and triggering injury. It is important to ask about a history of keloid formation before any elective surgery or piercing
• Skin biopsy: Not routinely needed but may be performed to exclude other conditions. Histology shows thick, hyalinized (glassy) collagen bundles arranged haphazardly in keloids, compared to the parallel arrangement seen in hypertrophic scars
• Differential diagnosis: Dermatofibroma, dermatofibrosarcoma protuberans (DFSP), lobomycosis, and morphea (localized scleroderma) may occasionally resemble keloid scars and should be considered if the presentation is atypical

What treatment options are available?

There is no single cure for keloids, and recurrence after treatment is common. The most effective approach combines multiple treatments (multimodal therapy). Hypertrophic scars have a better prognosis and often improve with conservative measures alone.

Prevention (the most effective strategy):

• Avoid unnecessary surgery, piercings, or tattoos if you are prone to keloids
• If surgery is needed, inform your surgeon about your scarring history so that preventive measures can be used
• Silicone gel sheets or silicone gel applied to fresh wounds can help prevent abnormal scarring
• Tension-reducing wound closure techniques and careful postoperative care reduce risk

First-line treatment:

• Silicone gel sheets or gel: The gold standard for non-invasive treatment and prevention. Worn over the scar for at least 12 hours per day for 3–6 months. Evidence-based, safe, and well tolerated
• Intralesional corticosteroid injections: Triamcinolone acetonide (10–40 mg/mL) injected directly into the scar every 4–6 weeks. The most commonly used active treatment — can flatten keloids and relieve itching and pain. Side effects include skin thinning (atrophy), depigmentation, and telangiectasias at the injection site

Second-line and combination treatments:

• Intralesional 5-fluorouracil (5-FU): Often combined with corticosteroids for improved results and fewer side effects. Effective for flattening and softening resistant scars
• Cryotherapy: Freezing the scar tissue — can be effective for small keloids; may cause depigmentation
• Laser therapy: Pulsed dye laser (PDL) can reduce redness and improve texture; fractional CO₂ laser may enhance drug delivery. Evidence remains limited but promising
• Pressure therapy: Compression garments or pressure earrings, especially useful for ear keloids and burns-related hypertrophic scars. Must be worn consistently for many months
• Surgical excision: Removing the keloid surgically — but excision alone has a recurrence rate of 45–100%. Always combined with adjuvant therapy (corticosteroid injections, radiation, or 5-FU) to reduce recurrence
• Radiotherapy: Post-excision superficial radiotherapy or brachytherapy significantly reduces recurrence. Reserved for severe, recurrent keloids that have failed other treatments

Emerging treatments: Botulinum toxin A (injected into the scar to reduce tension and symptoms), intralesional verapamil, and biologic therapies targeting specific inflammatory pathways are under investigation. These are not yet standard treatments.

Key points for patients

• Keloids and hypertrophic scars are not dangerous — they are benign, but they can cause significant discomfort and affect quality of life
• Prevention is key: If you know you scar easily or have a family history of keloids, avoid unnecessary skin procedures (piercings, tattoos, elective surgery) whenever possible
• There is no guaranteed cure for keloids — even the best treatments carry a risk of recurrence. Setting realistic expectations is important
• A multimodal approach (combining treatments) is consistently more effective than any single treatment
• Silicone products (sheets or gel) are safe, effective, and should be started early on any wound in a keloid-prone individual
• When to seek medical attention: Any scar that continues to grow, becomes painful or intensely itchy, restricts movement, or causes emotional distress should be evaluated by a dermatologist. Seek prompt attention if a firm lump appears within a scar that looks different from the rest — rarely, other skin conditions can mimic keloids
• Treatment takes time — many therapies require weeks to months of consistent use before results become apparent. Patience and adherence are essential
• The psychological impact of keloids is real and valid — do not hesitate to discuss your concerns with your doctor, and consider psychological support if scarring significantly affects your wellbeing