Hypertrophic Scar vs Keloid: How to Tell Them Apart and Treat Each

Hypertrophic scar vs keloid: what is the difference?

Both scars are made of excess collagen laid down after an injury to the deeper dermis, and both can be red, firm, itchy and tender. A 2017 review argues they are two ends of one process: chronic inflammation in the reticular dermis, the deeper layer of the skin. Superficial injuries that do not reach that layer do not produce either scar, and the difference between the two reflects how intense, frequent and long-lasting the inflammation is ^[1].

In practice the difference is behaviour. A hypertrophic scar respects the edges of the original wound, usually appears within weeks, and often softens and flattens over 12 to 24 months. A keloid crosses those edges into normal skin, may appear months after a minor injury such as a pimple or a piercing, can keep enlarging for years and rarely regresses by itself.

Keloid or hypertrophic scar: how can you tell which you have?

A few questions point the way. Did the scar stay where the cut, burn or spot was, or has it spread past it? Did it thicken soon after the wound healed and then begin to settle, or is it still growing a year later? Is it on a site under constant stretch, such as the breastbone or shoulder? Have you, or has anyone in your family, had a keloid before? A scar that stays in the wound and is improving behaves like a hypertrophic scar; one that spreads and keeps growing behaves like a keloid.

Clinicians formalise this. The Japan Scar Workshop consensus, written partly because Asian and African patients are highly prone to these scars, uses a scoring tool, the JSW Scar Scale, that combines the patient’s risk factors with the features of the scar to separate keloids, hypertrophic scars and mature scars and to judge severity ^[2]. The same document sets out how to tell pathological scars from benign and malignant growths that can mimic them, which is why a lump that appeared without any injury, grows quickly, bleeds or ulcerates is examined, and sometimes sampled, before it is treated as a keloid.

Some scars do not fit neatly. An early keloid can look like a hypertrophic scar for the first few months, so the label is sometimes revised over several visits. Flat red or brown marks after acne are not raised scars at all; see PIE vs PIH acne marks.

Hypertrophic scar treatment vs keloid treatment: what does the evidence show?

The tools overlap; the intensity differs. A young hypertrophic scar is often managed with silicone, time and, if it is still thick and itchy after a few months, steroid injections into the scar. A keloid usually starts with injections, because silicone alone rarely flattens an established keloid, and its plan assumes a longer course and follow-up for recurrence.

The evidence is real but not strong. A Cochrane review of 20 trials in 873 people found that silicone gel sheeting reduced the incidence of hypertrophic scarring in people prone to it (risk ratio 0.46) and reduced the thickness and redness of existing scars, but judged the trials highly susceptible to bias ^[4]. A meta-analysis of controlled trials found that triamcinolone injections reduced keloid size compared with no treatment and with silicone gel sheets, while noting that most trials were small and used inconsistent outcome measures ^[5].

What does a keloid injection involve, and does it work?

A keloid injection places a corticosteroid, commonly triamcinolone (a prescription medicine), directly into the body of the scar with a fine needle. The steroid dampens the inflammation that keeps fibroblasts producing collagen. Over a series of injections, usually four to six weeks apart, the scar tends to become flatter, softer and less itchy. Firm keloids resist the needle, so numbing cream and a slow technique help.

The main side effects are local: thinning of the skin around the scar, a paler patch, small visible vessels, or a slight dip if steroid reaches the fat beneath. Doses are kept to what the scar needs and adjusted at each visit for that reason. For scars that respond poorly, an anti-scarring medicine such as 5-fluorouracil is sometimes combined with the steroid; that choice is made case by case.

After a keloid has been cut out, injections are one way to lower the chance of it returning. Recurrence as high as 100% has been reported after excision alone, and studies define recurrence in different ways, which makes them hard to compare ^[7]. In a 2026 meta-analysis of 45 studies covering 1,885 earlobe keloids, recurrence after excision was about 12% with adjuvant steroid injections and 13% with radiotherapy; the authors noted that the steroid route needed four to six monthly injections ^[6]. Earlobes are a favourable site; keloids on the chest and shoulders, which are under constant stretch, behave less well.

Who gets raised scars, and can they be prevented?

Raised scars are common after injuries that reach the deeper dermis. In a systematic review of 48 articles on burns, the reported prevalence of hypertrophic scarring ranged from 32 to 72%, and risk factors included dark skin, female sex, young age, burns on the neck and upper limb, and slow healing ^[3]. Keloids are more frequent in Asian and African skin ^[2] and run in families; in Singapore, earlobe piercings and acne on the chest and shoulders are common triggers.

Prevention is mostly about the next wound. If you have formed a keloid before, tell any doctor operating on you, avoid elective piercings and tattoos at keloid-prone sites, start silicone once a surgical wound has closed, and have a scar that thickens or itches in its first weeks reviewed early. Treating chest and back acne promptly removes a common trigger; see back acne treatment. A raised scar treated in its first months usually needs less treatment than one that has grown for years.

How are raised scars treated at IN Eternity Clinic?

Dr Sin Yong first decides which scar it is. He examines the borders against the history of the original wound, measures and photographs the scar, and asks about previous treatment, the number of injections already given and any family history of keloids. Anything atypical, such as ulceration, bleeding or very fast growth, is examined further or referred before treatment.

For most raised scars the plan is steroid injections into the scar every four to six weeks, with silicone gel or sheets between visits. Laser is used selectively, mainly for redness and texture once a scar has been flattened; a scar that is still growing is treated with injections first. Where cutting out a keloid with radiotherapy or another adjuvant is the better route, for example a large earlobe keloid, Dr Sin Yong arranges a referral to a hospital team. Success is a scar that is flatter, softer, paler and no longer itchy, not one that disappears, and follow-up continues because keloids can return. Suitability is decided at an in-person assessment and results vary. See keloid and hypertrophic scar treatment, scar removal and acne scar treatment.

Frequently asked questions

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IN Eternity Clinic, 9 Scotts Road, #12-01 Pacific Plaza, Singapore 228210. By appointment with Medical Director Dr Sin Yong. Monday to Saturday, 11am to 8pm. WhatsApp or call +65 8815 3008. At IN Eternity Clinic a consultation fee applies, and it is waived if you go ahead with any medical treatment; the fee is S$120.