Keloids and Hypertrophic Scars

Table of Contents

1. How the Two Scars Differ
2. Who Gets Them
3. What Sets Them Off
4. The Biology in Plain Words
5. Treatments and What the Trials Found
6. Surgery Alone and Surgery With Follow-Up Treatment
7. Side Effects Reported for Each Treatment
8. Prevention After Surgery or Piercing in the Studies
9. Home and Traditional Measures People Report
10. Signs That Can Mean a Different Growth
11. What Is Not Known
12. Key Research Papers
13. Connections
14. Featured Videos

How the Two Scars Differ

Both scars are made of the same raw material — excess collagen, the protein that gives skin its strength — and both start after an injury to the deeper skin. The differences are in where they stop and what they do over time.

• Edges: a hypertrophic scar stays within the borders of the original wound; a keloid spreads beyond the original wound into healthy skin.
• Course over time: a hypertrophic scar settles on its own — a 2023 review describes spontaneous regression over 12 to 24 months; a keloid does not regress on its own, and the same review describes keloids enlarging and progressing over decades.
• After surgical removal: for hypertrophic scars, surgery is the first choice mainly when the scar pulls the skin tight (a contracture); for keloids, recurrence after cutting them out alone is reported in 45% to almost 100% of cases.
• Family pattern: hypertrophic scars are linked more to the injury itself (burn severity, healing time, skin tension); keloids often run in families, most commonly as an autosomal dominant trait.

The French review by Delaleu and colleagues (2023) puts the contrast plainly: keloids are "chronic progressive dermal pseudo-tumors" that can grow considerably but do not invade other tissues, while hypertrophic scars are a keloid-like process that does not extend beyond the injury and regresses within 12 to 24 months. A review of steroid injection by Morelli Coppola and colleagues (2018) adds that keloids "do not spontaneously regress, often continuing to grow over time."

Not every expert sees them as two separate diseases. Ogawa (2017) argues that the clinical differences between keloids and hypertrophic scars "merely reflect differences in the intensity, frequency, and duration" of inflammation in the deeper skin — in that view they sit on one spectrum, with keloids at the severe end. The same author's 2020 treatment update divides keloids into small single ones and large multiple ones, because the two groups are managed differently.

Timing also separates them in practice. In five families studied at the United States National Institutes of Health (Clark and colleagues, 2009), keloids most often first appeared by the second decade of life. After treatment, keloids can come back long after the skin looks settled: in a systematic review of surgery plus radiation, recurrences appeared between 2 and 36 months after treatment, with a mean of 15 months (van Leeuwen and colleagues, 2015).

Back to Table of Contents

Who Gets Them

Keloids

Keloids affect people of every background, but the measured rates differ a great deal between populations.

• Four countries: a street survey of 402 people (Stanley and colleagues, 2023) found self-identified keloids in 11% of respondents in Ghana, 7% in England, 6% in Australia and 2% in Canada.
• Cameroon: among 2,940 people seen at five dermatology clinics in Yaoundé, 102 had keloids — 3.5% (Kouotou and colleagues, 2019). Two thirds of the keloids followed an injury, two thirds itched, and the most common site was the front of the chest over the breastbone (26.5%). A family history of keloids raised the odds about fourfold (adjusted odds ratio 4.2).
• Taiwan: in a national insurance sample of 1 million people, the yearly rate of new keloids was 0.15%, with women outnumbering men 1.33 to 1 (Sun and colleagues, 2014).
• United States: in electronic health records covering 2015 to 2021, 5,457 adults with keloids were identified; 61.8% were women, the mean age was 34.2 years, and they were more often non-Hispanic Black, Hispanic or Asian than people without keloids (Olopoenia and colleagues, 2024). A large share of the keloids had never been treated.

Family history. In the five multigenerational families studied by Clark and colleagues (2009) — three African American, one Afro-Caribbean and one Asian-American — between 38% and 73% of family members had keloids. Some families tended to get them in particular places, one on the arms and legs and two in the armpits and groin. A Japanese genome-wide study of 824 people with keloids and 3,205 without found four genetic markers in three chromosome regions linked to keloids, the strongest raising the odds by about 1.8 times (Nakashima and colleagues, 2010).

Age and sex. At one of Japan's largest keloid referral centres, 131 of 1,443 keloid patients had keloids that began before age 10. Of these children, 80.9% were girls, 38.9% had a family history of keloids, and 48.9% had allergy-related conditions such as asthma, eczema or hay fever (Noishiki and colleagues, 2023).

Blood pressure and other conditions. In 304 Japanese keloid patients, higher blood pressure went with larger and more numerous keloids, although high blood pressure itself was not more common than in the general Japanese population (Arima and colleagues, 2015). The Taiwanese study found that women with uterine fibroids had 2.25 times the risk of keloids (Sun and colleagues, 2014), and the United States records showed more obesity, high blood pressure, high blood fats and diabetes in people with keloids (Olopoenia and colleagues, 2024). These are associations; they do not show that one condition causes the other. The site's high blood pressure and uterine fibroids pages cover those conditions.

Hypertrophic scars

Hypertrophic scars are far more common than keloids after major injury. A systematic review of 48 burn studies found hypertrophic scarring in between 32% and 72% of burn patients (Lawrence and colleagues, 2012). Risk factors in those studies were dark skin, female sex, young age, burns on the neck and upper limb, multiple operations, meshed skin grafts, a longer time to heal, and burn severity. In a Dutch study that followed heart and chest surgery patients for a year, higher body mass index, ethnic background and features of the scar itself went with more hypertrophic scarring, while taking blood pressure medicines went with less (Butzelaar and colleagues, 2015).

Back to Table of Contents

What Sets Them Off

Ogawa's 2017 review lists the injuries that lead to keloids and hypertrophic scars: trauma, insect bites, burns, surgery, vaccination, skin piercing, acne, folliculitis (inflamed hair follicles), chickenpox and shingles. The review makes one striking observation: injuries that stay in the upper skin and do not reach the deeper layer, the reticular dermis, "never cause" these scars.

• Ear piercing. In a survey of 32 people with keloids from ear piercing, half developed a keloid after their first piercing and 20 developed keloids after later piercings. Those pierced at age 11 or older were more often affected (80%) than those pierced before age 11 (23.5%) (Lane and colleagues, 2005). In a long series treated with radiation after surgery, 7 of the 9 keloids that came back did so after the ear lobe was pierced again (Borok and colleagues, 1988).
• Vaccination. In the Japanese childhood series, vaccination was the most common trigger (47.5%), followed by chickenpox (19.9%). The tuberculosis vaccine (Bacille Calmette-Guérin, BCG) was the most common vaccine trigger, and 92.9% of keloids from it were in girls. The chest was the most common site in boys (30.0%), the arm in girls (41.1%) (Noishiki and colleagues, 2023).
• Surgery. Chest operations through the breastbone are a well-studied source; one trial below treated keloidal and hypertrophic scars from exactly that incision (Manuskiatti and Fitzpatrick, 2002).
• Burns. See the burn figures above; burn scars are the main subject of the pressure-garment research.
• Acne and folliculitis. Both are on Ogawa's list of triggers; deep, inflamed acne lesions are the ones that scar. The site's acne and folliculitis pages cover those conditions.
• No known injury. "Spontaneous" keloids — those with no significant history of trauma — have been reported mainly with rare inherited syndromes such as Rubinstein-Taybi, Dubowitz and Noonan syndromes, and in some people with allergic (atopic) conditions. A 2018 review notes that they are hard to confirm, because a very minor injury or bout of inflammation may have been the real trigger (Jfri and Alajmi, 2018).

Where keloids appear is not random. The Cameroonian clinics found the front of the chest most often affected, the Japanese childhood series found the chest and the arm most often affected, and the ear lobe is the typical site after piercing. Ogawa's 2020 update names tension on the wound or scar as a local risk factor — the chest and shoulders are places where the skin is stretched by breathing and arm movement.

Back to Table of Contents

The Biology in Plain Words

Normal healing runs in stages: bleeding stops, inflammation cleans the wound, cells called fibroblasts lay down new collagen, and then over months the scar is remodelled and softened. The site's wound-healing animation shows those stages.

In keloids and hypertrophic scars, the inflammation stage does not end. Ogawa (2017) describes the deeper skin of these scars as packed with inflammatory cells, extra fibroblasts, new blood vessels and collagen. Signalling molecules that drive inflammation — interleukin-1 alpha and beta, interleukin-6 and tumour necrosis factor alpha — are raised in keloid tissue. In this view keloids are better understood as an inflammatory disorder of the deeper skin than as a skin tumour. The review points out that nearly every treatment that works — steroid, radiation, freezing, pressure, 5-fluorouracil and surgery that reduces skin tension — acts by reducing that inflammation.

Three kinds of factors seem to push the process along:

• Local: stretching forces on the wound and slow, prolonged healing.
• Body-wide: high blood pressure, pregnancy and female sex are listed as factors that worsen keloids (Noishiki and colleagues, 2023; Arima and colleagues, 2015).
• Genetic: the inherited family patterns and the gene regions found in the Japanese genome study, including one in a gene called NEDD4 (Nakashima and colleagues, 2010).

The plant compounds in gotu kola have been tested on keloid fibroblasts grown in a dish; that cell research is described on the site's gotu kola for wound healing and scars page.

Back to Table of Contents

Treatments and What the Trials Found

A 2018 review states that no universally effective therapy for keloids has been found (Morelli Coppola and colleagues). A 2023 review of 25 randomised trials with at least 20 patients each found that injections into the scar reduced scarring by an average of 64.1%, compared with 29.9% for physical treatments and 34% for creams and gels (Worley and colleagues, 2023). The details for each treatment follow.

Silicone gel sheets and silicone gel

The 2013 Cochrane review (O'Brien and Jones) included 20 trials with 873 people aged 1.5 to 81 years. For prevention in people prone to raised scars, silicone gel sheeting lowered the rate of hypertrophic scarring compared with no treatment (risk ratio 0.46 — roughly half the rate). For existing scars it reduced thickness and improved colour. The reviewers rated the evidence as weak: the trials were of poor quality and "highly susceptible to bias." A 2020 analysis of six trials (375 patients) found that silicone gel reduced pigmentation, height and stiffness scores after surgery compared with placebo or nothing, and that the gel and the sheet performed about the same; silicone gel was also no better than other non-silicone creams in the trials that compared them (Wang and colleagues, 2020).

Pressure garments

Tight elastic garments are standard care for burn scars worldwide. The 2024 Cochrane review (Harris and colleagues) included 15 trials with 1,179 participants and found the evidence "very uncertain" for every comparison, concluding there is insufficient evidence for or against pressure garments in preventing hypertrophic burn scars. It noted that the full effect of any scar treatment may not be seen until about 18 months, while most trials followed people for less time. An earlier analysis of 12 trials with 710 patients found that pressure of 15 to 25 millimetres of mercury modestly improved scar scores, thickness and hardness but not blood-vessel content (Ai and colleagues, 2017).

Steroid injection into the scar

Triamcinolone acetonide, a corticosteroid, injected directly into the scar is the most common first treatment for keloids. A 2018 review reports that steroid injection alone gives 50% to 100% regression, with recurrence of 33% after one year and 50% after five years (Morelli Coppola and colleagues).

5-fluorouracil injection

5-fluorouracil is a cancer medicine that slows dividing cells; in keloids it is injected in small amounts into the scar. A review of 18 papers covering 482 patients found it effective in 45% to 96% of patients, but only the steroid-plus-5-fluorouracil mixture showed signs of beating steroid alone (Bijlard and colleagues, 2015). In a Finnish randomised trial of 43 patients with 50 keloids, the six-month remission rate was 46% with 5-fluorouracil and 60% with triamcinolone, a difference that was not statistically significant (Hietanen and colleagues, 2019).

The combination has the strongest trial record. A 2023 meta-analysis of 13 studies (12 randomised) found the mixture of triamcinolone and 5-fluorouracil to give about three and a half times the odds of a good result compared with triamcinolone alone (odds ratio 3.45) and about four times the odds compared with 5-fluorouracil alone (odds ratio 4.17) (Mavilakandy and colleagues, 2023). A 2025 network meta-analysis of 22 randomised trials (1,398 cases) found that only combinations containing both drugs beat triamcinolone alone, with the mixture plus pulsed dye laser ranking highest (Chandra and colleagues, 2025).

Freezing (cryotherapy)

Freezing can be applied to the surface or from inside the scar with a needle-shaped probe. In 10 patients with 12 scars treated once from inside, scar volume fell by an average of 51.4%, with no recurrence over 18 months (Har-Shai and colleagues, 2003). A larger Dutch study of 27 patients with 29 keloids, including all skin types, found an average volume reduction of 63% at 12 months, but 24% of the keloids came back (van Leeuwen and colleagues, 2015).

Laser

A systematic review of eight randomised trials found that the pulsed dye laser, which targets blood vessels in the scar, may improve overall appearance more than conventional treatment, though results were similar when individual scar features were measured (de las Alas and colleagues, 2012). In a randomised trial on breastbone surgery scars, steroid, 5-fluorouracil, the mixture and the pulsed dye laser all improved the scars about equally; the injections worked faster, the laser did better on texture (Manuskiatti and Fitzpatrick, 2002). In a Thai trial of 22 keloid patients, fractional carbon dioxide laser with steroid applied on top completely cleared the keloids in 63.6% of patients and injected steroid in 72.7%; recurrence over a year was 9.1% and 18.2% respectively (Tawaranurak and colleagues, 2022). The 2023 review of 25 trials found that laser response was linked to skin type, with more benefit in lighter skin (Fitzpatrick types I to III) than darker skin (types IV to VI) (Worley and colleagues, 2023). Laser alone is reported to carry a high recurrence rate for keloids (Morelli Coppola and colleagues, 2018).

Botulinum toxin

Botulinum toxin type A relaxes muscle and may reduce the pulling force on a healing wound. A 2024 meta-analysis of seven randomised trials found it improved overall scar scores and softness, but not scar height or thickness, redness from blood vessels, or colour (Raslan and colleagues, 2024). A 2019 meta-analysis, which included Chinese-language databases, concluded that injected botulinum toxin worked better than injected steroid or placebo (Bi and colleagues, 2019). The site's hyperhidrosis page covers another use of the same toxin.

Back to Table of Contents

Surgery Alone and Surgery With Follow-Up Treatment

Cutting a keloid out on its own usually fails. A 2023 systematic review states that recurrence after excision alone "is reported in almost 100% of cases" (Bjerremand and colleagues), and a 2024 meta-analysis cites earlier reported rates of 45% to 100% after complete excision (Lawera and colleagues). For that reason surgery for keloids is almost always combined with something else.

Surgery plus radiation. Low-dose radiation to the wound after excision has been used for over a century. The largest analysis, published in 2026, pooled 106 studies covering 10,745 keloids: recurrence was 18% with X-ray treatment, 14% with brachytherapy (a radiation source placed in or on the wound) and 16% with electron beam therapy (Seth and colleagues). In a United States series of 168 keloids treated by one surgeon, where every patient also had steroid and 5-fluorouracil injected at the time of surgery, recurrence was about 16% to 17% with radiation added and about 44% to 47% without it, on both ear and non-ear sites (Kumar and colleagues, 2026). An older series of 375 irradiated keloid sites treated from 1928 to 1986 reported recurrence of 2.4% (Borok and colleagues, 1988).

The studies disagree on timing. A 2015 review found lower recurrence when radiation began within 7 hours of surgery than after more than 24 hours, and lower recurrence with high-dose-rate brachytherapy (van Leeuwen and colleagues). A 2021 meta-analysis of 16 observational studies found the opposite for electron beam therapy — 3.80% recurrence when started more than 24 hours after surgery against 37.16% within 24 hours — and no difference for the other types (Hsieh and colleagues). The 2026 analysis found no significant difference between early and late radiation at all (Seth and colleagues).

Surgery plus steroid or other injections. A review of seven controlled trials of excision followed by steroid injection, radiation, silicone gel, pressure, verapamil or 5-fluorouracil found all reported promising results, but every study carried a high risk of bias (Bjerremand and colleagues, 2023). In the 2025 network meta-analysis, the lowest recurrence came with triamcinolone plus bleomycin and with triamcinolone plus 5-fluorouracil plus brachytherapy (Chandra and colleagues, 2025).

Removing the inside only. One surgical technique cuts out the inside of the keloid and leaves its outer rim in place. A meta-analysis of 22 studies covering 608 keloids found a pooled recurrence of 13% with this "intralesional" excision, followed for an average of 19.2 months (Lawera and colleagues, 2024). Adding other therapies made no measurable difference to that rate.

Back to Table of Contents

Side Effects Reported for Each Treatment

• Steroid injection: thinning of the skin (atrophy), small visible blood vessels (telangiectasia) and lighter skin (hypopigmentation). In the Finnish trial, skin thinning occurred in 44% of steroid-treated keloids against 8% with 5-fluorouracil, and visible blood vessels in 50% against 21% (Hietanen and colleagues, 2019). In the breastbone scar trial, half of the segments treated with steroid alone (5 of 10) showed thinning, lighter skin or visible vessels; no long-term problems were seen with the other treatments (Manuskiatti and Fitzpatrick, 2002). Adding 5-fluorouracil to the steroid cut the rate of visible vessels (odds ratio 0.24) (Mavilakandy and colleagues, 2023).
• 5-fluorouracil: findings conflict. A 2018 review reports more side effects with 5-fluorouracil alone than with steroid alone, and fewer with the combination than with either (Morelli Coppola and colleagues), while the Finnish trial found fewer local effects with 5-fluorouracil.
• Freezing: loss of skin colour. In the Dutch study, lighter skin recovered in 69% of keloids within 12 months, but persistent lightening was more common in African American patients (van Leeuwen and colleagues, 2015). The smaller Israeli study reported only mild swelling and blistering and no permanent loss of colour (Har-Shai and colleagues, 2003).
• Radiation: in the 2026 pooled analysis, complication rates were 9% for X-ray, 18% for brachytherapy and 16% for electron beam (Seth and colleagues). In the United States series, radiation side effects were more common at non-ear sites (37%) than on the ear (20%) (Kumar and colleagues, 2026). In the 1928–1986 series, temporary darkening of the skin occurred in 24% of sites (Borok and colleagues, 1988).
• Radiation and cancer: a search of the literature from 1901 to 2009 found five reported cancers associated with keloid radiation — including a fibrosarcoma, a basal cell carcinoma, thyroid cancer and breast cancer — in cases where it was unclear whether the dose was appropriate or nearby tissue was shielded (Ogawa and colleagues, 2009). About 80% of radiation oncologists surveyed considered radiation acceptable for keloids. The authors concluded the risk is very low when the thyroid and breast are shielded, "especially in children and infants." The 1988 series reported no cancers (Borok and colleagues).
• Botulinum toxin: a meta-analysis of 16 trials found no significant difference in adverse events between toxin and control (Fu and colleagues, 2022).
• Pressure garments: the Cochrane review found the evidence on harms and on how well people keep wearing them "very uncertain", and possibly fewer problems with silicone than with garments (Harris and colleagues, 2024).
• Topical gels: in an onion-extract trial, 13.6% of people had mild stinging that went away on its own (Draelos and colleagues, 2012). Vitamin E rubbed on surgical scars caused a skin allergy (contact dermatitis) in 33% of people in one trial (Baumann and Spencer, 1999).

Back to Table of Contents

Prevention After Surgery or Piercing in the Studies

• Silicone after surgery: silicone sheeting roughly halved the rate of hypertrophic scars in people prone to them, with weak evidence (O'Brien and Jones, 2013); silicone gel reduced height, pigmentation and stiffness after operations (Wang and colleagues, 2020).
• Botulinum toxin at the time of surgery: 16 randomised trials covering 671 wounds in 510 patients found better scar scores, narrower scars and more satisfied patients with toxin than with placebo or nothing, with the clearest effect in facial wounds of Asian patients (Fu and colleagues, 2022).
• Reducing tension: Ogawa's 2020 update lists tension on the wound as a key local factor and includes tape fixation of the wound among the conservative measures.
• Blood pressure: the Dutch chest-surgery study found fewer hypertrophic scars in people taking blood pressure medicines (Butzelaar and colleagues, 2015). This is an association, not a trial.
• Piercing: the ear-piercing survey found keloids more often in people pierced at age 11 or older, a pattern that also held in people with a family history (Lane and colleagues, 2005). The study was small (32 people) and surveyed only people who already had keloids. Its authors concluded that keloids are more likely when ears are pierced after age 11.
• Re-piercing after treatment: 7 of 9 recurrences in the 1988 radiation series followed re-piercing of the treated ear (Borok and colleagues).
• Long follow-up: because recurrences appear up to 36 months later (van Leeuwen and colleagues, 2015), the 2020 treatment algorithm states that patients are followed over the long term (Ogawa, 2022).

Back to Table of Contents

Home and Traditional Measures People Report

Many people treat raised scars at home with creams, oils and plant extracts. The measures below are what people report using; the trial results that exist are given beside them.

Onion extract gel

Onion (Allium cepa) extract gels are sold over the counter for scars. Four small trials point in different directions:

• In 17 patients after Mohs skin surgery, onion gel did not improve redness or itching over one month; a plain petroleum ointment did reduce redness (Jackson and Shelton, 1999).
• In 24 patients whose new surgical scars were split in half, onion gel and petroleum ointment gave no difference in appearance, redness, thickening, itching or pain (Chung and colleagues, 2006).
• In 44 people with two small chest wounds, the treated side looked better than the untreated side after four and eight weeks. The trial was funded by the gel's maker and four authors were its employees (Draelos and colleagues, 2012). The comparison was against nothing, not against a plain ointment.
• In 20 Asian women in Bangkok with caesarean-section scars (16 finished), 12% onion gel improved scar height and symptoms but not redness, stiffness or overall appearance compared with placebo (Chanprapaph and colleagues, 2012).

Vitamin E oil

Breaking open vitamin E capsules onto a scar is a common home practice. In a double-blind trial of 15 people after skin-cancer surgery, vitamin E mixed into ointment had no effect on, or worsened, the appearance of the scar in 90% of cases, and 33% developed contact dermatitis (Baumann and Spencer, 1999). The site's vitamin E and skin health page reviews the wider evidence.

Gotu kola (Centella asiatica)

Gotu kola has a long traditional use for wounds in Asian medicine, and a purified extract was sold as a scar medicine in Europe. A 1979 report on that extract described it as "of clinical value in stopping the inflammatory phase of hypertrophic scars and keloids" and reported a placebo response of 29% (Bossé and colleagues, 1979); the abstract gives no patient numbers. In a 2023 Turkish trial, 280 patients after wrist surgery were randomised to a 1% gotu kola cream for six months or nothing; the cream group had better scar scores at three to six months and better hand function at six months (Balevi and Balevi, 2023). That trial was about ordinary surgical scars, not keloids. The site's gotu kola scar page covers this in depth.

Massage, moisturisers and covering the scar

Scar massage, cocoa butter and keeping a new scar out of the sun are widely used; the site's wound healing page describes them. Two of the onion trials above found that a plain petroleum ointment did as well as or better than the onion gel, which suggests that keeping the scar moist accounts for much of what people notice. No trial found here tested these measures on keloids themselves.

Back to Table of Contents

Signs That Can Mean a Different Growth

Most firm lumps in a scar are keloids or hypertrophic scars. Published case reports describe other growths that were first taken for keloids:

• A 73-year-old woman with lung cancer treated 20 months earlier had firm, plum-coloured lumps on her side, referred as suspected keloids. A small tissue sample (biopsy) showed the lung cancer had spread to the skin (Newcomer and colleagues, 2022). The authors describe such skin spread as nodular, firm, fixed and flesh-coloured to reddish-purple.
• A 71-year-old woman with a scalp lump at a previous surgical site had a skin muscle-cell cancer (dermal leiomyosarcoma) that was diagnosed late because it looked like a keloid. The authors note that the two are hard to tell apart, especially when the person has a history of wounds or surgery in that spot (Hwang and colleagues, 2021).
• A patient first diagnosed with a keloid was found on biopsy to have a lymphoma of the skin (Kong and Deng, 2023).

The features in these reports were a lump with no clear injury behind it, a lump in an older person with a past cancer, firm purple or fixed lumps, and a lump growing where it would not be expected. Spontaneous keloids with no injury are themselves rare and hard to confirm (Jfri and Alajmi, 2018). In each report the diagnosis was made by examining tissue under the microscope.

Back to Table of Contents

What Is Not Known

• Which treatment is best. Reviews keep finding trials that are small, short and at high risk of bias (O'Brien and Jones, 2013; Bjerremand and colleagues, 2023). Standard measures differ from study to study.
• Whether pressure garments work. They are standard care for burns, yet the 2024 Cochrane review rated the evidence very uncertain.
• When to give radiation. Three reviews reached three different conclusions on timing.
• Long-term recurrence. Keloids can return up to three years later, and many studies stop before then.
• Darker skin. Keloids are most common in people of African descent, yet laser responses and freezing side effects differ by skin type, and early freezing studies included only lighter-skinned patients (van Leeuwen and colleagues, 2015; Worley and colleagues, 2023).
• What blood pressure, fibroids and allergy have to do with it. The links are measured associations; whether treating any of them changes keloids has not been tested in trials.
• Home measures on keloids. The onion, vitamin E and gotu kola trials were on ordinary surgical scars; none tested an established keloid.

Back to Table of Contents

Key Research Papers

1. Delaleu J, Charvet E, Petit A. Keloid disease: Review with clinical atlas. Part I: Definitions, history, epidemiology, clinics and diagnosis. Ann Dermatol Venereol. 2023;150(1):3-15. PubMed PMID: 36494213
2. Morelli Coppola M, Salzillo R, Segreto F, Persichetti P. Triamcinolone acetonide intralesional injection for the treatment of keloid scars: patient selection and perspectives. Clin Cosmet Investig Dermatol. 2018;11:387-396. PubMed PMID: 30087573
3. Ogawa R. Keloid and Hypertrophic Scars Are the Result of Chronic Inflammation in the Reticular Dermis. Int J Mol Sci. 2017;18(3):606. PubMed PMID: 28287424
4. Ogawa R. The Most Current Algorithms for the Treatment and Prevention of Hypertrophic Scars and Keloids: A 2020 Update of the Algorithms Published 10 Years Ago. Plast Reconstr Surg. 2022;149(1):79e-94e. PubMed PMID: 34813576
5. Clark JA, Turner ML, Howard L, Stanescu H, Kleta R, Kopp JB. Description of familial keloids in five pedigrees: evidence for autosomal dominant inheritance and phenotypic heterogeneity. BMC Dermatol. 2009;9:8. PubMed PMID: 19638218
6. van Leeuwen MC, Stokmans SC, Bulstra AE, Meijer OW, Heymans MW, Ket JC, et al. Surgical Excision with Adjuvant Irradiation for Treatment of Keloid Scars: A Systematic Review. Plast Reconstr Surg Glob Open. 2015;3(7):e440. PubMed PMID: 26301129
7. Stanley GHM, Pitt ER, Lim D, Pleat J. Prevalence, exposure and the public knowledge of keloids on four continents. J Plast Reconstr Aesthet Surg. 2023;77:359-370. PubMed PMID: 36621239
8. Kouotou EA, Nansseu JR, Omona Guissana E, Mendouga Menye CR, Akpadjan F, Tounkara TM, et al. Epidemiology and clinical features of keloids in Black Africans: a nested case-control study from Yaoundé, Cameroon. Int J Dermatol. 2019;58(10):1135-1140. PubMed PMID: 31429935
9. Sun LM, Wang KH, Lee YC. Keloid incidence in Asian people and its comorbidity with other fibrosis-related diseases: a nationwide population-based study. Arch Dermatol Res. 2014;306(9):803-8. PubMed PMID: 25081927
10. Olopoenia A, Yamaguchi Y, Peeva E, Berman B, Jagun O, George P. Demographics, clinical characteristics, and treatment patterns among keloid patients: United States Electronic Health Records (EHR) Database Study. Int J Dermatol. 2024;63(8):e163-e170. PubMed PMID: 38411301
11. Nakashima M, Chung S, Takahashi A, Kamatani N, Kawaguchi T, Tsunoda T, et al. A genome-wide association study identifies four susceptibility loci for keloid in the Japanese population. Nat Genet. 2010;42(9):768-71. PubMed PMID: 20711176
12. Noishiki C, Hayasaka Y, Yoshida R, Ogawa R. Over 90% of Childhood BCG Vaccine-Induced Keloids in Japan Occur in Women. Dermatol Ther (Heidelb). 2023;13(5):1137-1147. PubMed PMID: 36952124
13. Arima J, Huang C, Rosner B, Akaishi S, Ogawa R. Hypertension: a systemic key to understanding local keloid severity. Wound Repair Regen. 2015;23(2):213-21. PubMed PMID: 25728259
14. Lawrence JW, Mason ST, Schomer K, Klein MB. Epidemiology and impact of scarring after burn injury: a systematic review of the literature. J Burn Care Res. 2012;33(1):136-46. PubMed PMID: 22138807
15. Butzelaar L, Soykan EA, Galindo Garre F, Beelen RH, Ulrich MM, Niessen FB, et al. Going into surgery: Risk factors for hypertrophic scarring. Wound Repair Regen. 2015;23(4):531-7. PubMed PMID: 25857804
16. Lane JE, Waller JL, Davis LS. Relationship between age of ear piercing and keloid formation. Pediatrics. 2005;115(5):1312-4. PubMed PMID: 15867040
17. Borok TL, Bray M, Sinclair I, Plafker J, LaBirth L, Rollins C. Role of ionizing irradiation for 393 keloids. Int J Radiat Oncol Biol Phys. 1988;15(4):865-70. PubMed PMID: 3182326
18. Jfri A, Alajmi A. Spontaneous Keloids: A Literature Review. Dermatology. 2018;234(3-4):127-130. PubMed PMID: 30114700
19. Worley B, Kim K, Jain-Poster K, Reynolds KA, Merkel EA, Kang BY, et al. Treatment of traumatic hypertrophic scars and keloids: a systematic review of randomized control trials. Arch Dermatol Res. 2023;315(7):1887-1896. PubMed PMID: 36781457
20. O'Brien L, Jones DJ. Silicone gel sheeting for preventing and treating hypertrophic and keloid scars. Cochrane Database Syst Rev. 2013;2013(9):CD003826. PubMed PMID: 24030657
21. Wang F, Li X, Wang X, Jiang X. Efficacy of topical silicone gel in scar management: A systematic review and meta-analysis of randomised controlled trials. Int Wound J. 2020;17(3):765-773. PubMed PMID: 32119763
22. Harris IM, Lee KC, Deeks JJ, Moore DJ, Moiemen NS, Dretzke J. Pressure-garment therapy for preventing hypertrophic scarring after burn injury. Cochrane Database Syst Rev. 2024;1(1):CD013530. PubMed PMID: 38189494
23. Ai JW, Liu JT, Pei SD, Liu Y, Li DS, Lin HM, et al. The effectiveness of pressure therapy (15-25 mmHg) for hypertrophic burn scars: A systematic review and meta-analysis. Sci Rep. 2017;7:40185. PubMed PMID: 28054644
24. Bijlard E, Steltenpool S, Niessen FB. Intralesional 5-fluorouracil in keloid treatment: a systematic review. Acta Derm Venereol. 2015;95(7):778-82. PubMed PMID: 25805099
25. Hietanen KE, Järvinen TA, Huhtala H, Tolonen TT, Kuokkanen HO, Kaartinen IS. Treatment of keloid scars with intralesional triamcinolone and 5-fluorouracil injections - a randomized controlled trial. J Plast Reconstr Aesthet Surg. 2019;72(1):4-11. PubMed PMID: 30448246
26. Mavilakandy AK, Vayalapra S, Minty I, Parekh JN, Charles WN, Khajuria A. Comparing Combination Triamcinolone Acetonide and 5-Fluorouracil with Monotherapy Triamcinolone Acetonide or 5-Fluorouracil in the Treatment of Hypertrophic Scars: A Systematic Review and Meta-Analysis. Plast Reconstr Surg. 2024;153(6):1318-1330. PubMed PMID: 37337341
27. Chandra AF, Kamayana J, Tunjung N, Rini IS. Comparative Efficacy and Recurrence of Combination Therapies in Keloid Management: A Systematic Review and Network Meta-analysis. Plast Reconstr Surg Glob Open. 2025;13(8):e7048. PubMed PMID: 40771257
28. Har-Shai Y, Amar M, Sabo E. Intralesional cryotherapy for enhancing the involution of hypertrophic scars and keloids. Plast Reconstr Surg. 2003;111(6):1841-52. PubMed PMID: 12711943
29. van Leeuwen MCE, van der Wal MBA, Bulstra AJ, Galindo-Garre F, Molier J, van Zuijlen PPM, et al. Intralesional cryotherapy for treatment of keloid scars: a prospective study. Plast Reconstr Surg. 2015;135(2):580-589. PubMed PMID: 25626801
30. de las Alas JM, Siripunvarapon AH, Dofitas BL. Pulsed dye laser for the treatment of keloid and hypertrophic scars: a systematic review. Expert Rev Med Devices. 2012;9(6):641-50. PubMed PMID: 23249157
31. Manuskiatti W, Fitzpatrick RE. Treatment response of keloidal and hypertrophic sternotomy scars: comparison among intralesional corticosteroid, 5-fluorouracil, and 585-nm flashlamp-pumped pulsed-dye laser treatments. Arch Dermatol. 2002;138(9):1149-55. PubMed PMID: 12224975
32. Tawaranurak N, Pliensiri P, Tawaranurak K. Combination of fractional carbon dioxide laser and topical triamcinolone vs intralesional triamcinolone for keloid treatment: A randomised clinical trial. Int Wound J. 2022;19(7):1729-1735. PubMed PMID: 35166029
33. Raslan EE, Bakhamees BH, Howsawi TA, Alshmrani LS, Alruwaili AG, Alhashmi AY, et al. The Efficacy of Botulinum Toxin Type A (BTA) in the Treatment of Hypertrophic Scars and Keloids: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Cureus. 2024;16(10):e71161. PubMed PMID: 39525161
34. Bi M, Sun P, Li D, Dong Z, Chen Z. Intralesional Injection of Botulinum Toxin Type A Compared with Intralesional Injection of Corticosteroid for the Treatment of Hypertrophic Scar and Keloid: A Systematic Review and Meta-Analysis. Med Sci Monit. 2019;25:2950-2958. PubMed PMID: 31006769
35. Bjerremand JR, Haerskjold A, Karmisholt KE. Excision and adjuvant treatment to prevent keloid recurrence. - a systematic review of prospective, clinical, controlled trials. J Plast Surg Hand Surg. 2023;57(1-6):38-45. PubMed PMID: 35848929
36. Lawera NG, Madzia J, Casey LC, Guyton RL, Woodyard De Brito KC, Kinzer A, et al. Keloid Intralesional Excision Reduces Recurrence: A Meta-analytic Study of the Available Literature on 608 Keloids. Plast Reconstr Surg Glob Open. 2024;12(3):e5652. PubMed PMID: 38463702
37. Seth I, Gibson D, Marcaccini G, Pentangelo P, Xie Y, Lim B, et al. Post-excisional radiotherapy for keloid treatment: A systematic review and meta-analysis. J Plast Reconstr Aesthet Surg. 2026;113:459-531. PubMed PMID: 41401628
38. Kumar SIS, Katta T, Anderson M, McRae C, Rallapalle V, Yerabolu K, et al. Regional Differences in Postexcision Outcomes of Keloids: A Focus on Auricular Versus Nonauricular Sites. Ann Plast Surg. 2026;97(1):24-29. PubMed PMID: 42184131
39. Hsieh CL, Chi KY, Lin WY, Lee LT. Timing of Adjuvant Radiotherapy After Keloid Excision: A Systematic Review and Meta-Analysis. Dermatol Surg. 2021;47(11):1438-1443. PubMed PMID: 34417379
40. Ogawa R, Yoshitatsu S, Yoshida K, Miyashita T. Is radiation therapy for keloids acceptable? The risk of radiation-induced carcinogenesis. Plast Reconstr Surg. 2009;124(4):1196-1201. PubMed PMID: 19935303
41. Fu Z, Huang H, Huang J. Efficacy and safety of botulinum toxin type A for postoperative scar prevention and wound healing improvement: A systematic review and meta-analysis. J Cosmet Dermatol. 2022;21(1):176-190. PubMed PMID: 34859567
42. Jackson BA, Shelton AJ. Pilot study evaluating topical onion extract as treatment for postsurgical scars. Dermatol Surg. 1999;25(4):267-9. PubMed PMID: 10417579
43. Chung VQ, Kelley L, Marra D, Jiang SB. Onion extract gel versus petrolatum emollient on new surgical scars: prospective double-blinded study. Dermatol Surg. 2006;32(2):193-7. PubMed PMID: 16442038
44. Draelos ZD, Baumann L, Fleischer AB Jr, Plaum S, Avakian EV, Hardas B. A new proprietary onion extract gel improves the appearance of new scars: a randomized, controlled, blinded-investigator study. J Clin Aesthet Dermatol. 2012;5(6):18-24. PubMed PMID: 22768353
45. Chanprapaph K, Tanrattanakorn S, Wattanakrai P, Wongkitisophon P, Vachiramon V. Effectiveness of onion extract gel on surgical scars in asians. Dermatol Res Pract. 2012;2012:212945. PubMed PMID: 22924037
46. Baumann LS, Spencer J. The effects of topical vitamin E on the cosmetic appearance of scars. Dermatol Surg. 1999;25(4):311-5. PubMed PMID: 10417589
47. Bossé JP, Papillon J, Frenette G, Dansereau J, Cadotte M, Le Lorier J. Clinical study of a new antikeloid agent. Ann Plast Surg. 1979;3(1):13-21. PubMed PMID: 396846
48. Balevi M, Balevi A. The effect of Centella Asiatica cream on scar development in patients who underwent open carpal tunnel release surgery. J Hand Ther. 2023;36(4):962-966. PubMed PMID: 36918311
49. Newcomer JB, Durbin A, Wilson C. Cutaneous Metastasis of Lung Adenocarcinoma: Initially Mimicking and Misdiagnosed as Keloids. Cureus. 2022;14(7):e27285. PubMed PMID: 36039229
50. Hwang YJ, Chung JH, Yoon ES. Scalp Reconstruction in Delayed Diagnosed Dermal Leiomyosarcoma Mimicking Keloid Scar. J Craniofac Surg. 2021;32(7):e620-e622. PubMed PMID: 33654031
51. Kong D, Deng D. A Case of Anaplastic Large Cell Lymphoma Misdiagnosed with Keloid. Clin Cosmet Investig Dermatol. 2023;16:1243-1248. PubMed PMID: 37200841

PubMed Topic Searches

1. PubMed: keloid treatment and recurrence in randomised trials
2. PubMed: hypertrophic scar prevention with silicone
3. PubMed: keloid excision with radiotherapy
4. PubMed: steroid and 5-fluorouracil injection for keloids
5. PubMed: keloid epidemiology and genetics
6. PubMed: onion extract and scars

Back to Table of Contents

Connections

• Dermatology — the parent section for skin conditions
• Wound Healing — what speeds normal repair and everyday scar care
• How a Wound Heals — the four phases, animated
• Gotu Kola for Wound Healing and Scars — the plant extract tested on scars
• Vitamin E and Skin Health — the scar trials in detail
• Acne — a common source of raised scars
• Folliculitis — inflamed hair follicles, another trigger
• Hidradenitis Suppurativa — a scarring skin disease
• High Blood Pressure — linked to keloid size and number
• Uterine Fibroids — another fibrous growth linked to keloids

Back to Table of Contents

Featured Videos