Scar

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All scarring is composed of the same collagen as the tissue it has replaced, but the composition of the scar tissue, compared to the normal tissue, is different. Scar tissue also lacks elasticity{{cite book | last = A. Bernard Ackerman, MD, Almut Böer, MD, Bruce Bennin, MD, Geoffrey J. Gottlieb, MD | title = Histologic Diagnosis of Inflammatory Skin Diseases An Algorithmic Method Based on Pattern Analysis: Embryologic, Histologic, and Anatomic Aspects: Elastic Fibers | publisher = Ardor Scribendi | edition = Third | date = January 2005 | pages = 522 | language = en | url = https://www.derm101.com/inflammatory/embryologic-histologic-and-anatomic-aspects/elastic-fibers/ | isbn = 9781893357259 | access-date = 19 September 2017 | archive-date = 20 June 2018 | archive-url = https://web.archive.org/web/20180620024213/https://www.derm101.com/inflammatory/embryologic-histologic-and-anatomic-aspects/elastic-fibers/ | url-status = dead }} unlike normal tissue which distributes fiber elasticity. Scars differ in the amounts of collagen overexpressed. Labels have been applied to the differences in overexpression. Two of the most common types are hypertrophic and keloid scarring, both of which experience excessive stiff collagen bundled growth overextending the tissue, blocking off regeneration of tissues. Another form is atrophic scarring (sunken scarring), which also has an overexpression of collagen blocking regeneration. This scar type is sunken, because the collagen bundles do not overextend the tissue. Stretch marks (striae) are regarded as scars by some.

High melanin levels and either African or Asian ancestry may make adverse scarring more noticeable.{{cite journal |doi=10.1016/j.sder.2009.04.002 |pmid=19608056 |title=Update on the Management of Keloids |journal=Seminars in Cutaneous Medicine and Surgery |volume=28 |issue=2 |pages=71–76 |year=2009 |last1=Kelly |first1=A. Paul |doi-broken-date=1 November 2024 }}

{{main|Hypertrophic scars}}

Hypertrophic scars occur when the body overproduces collagen, which causes the scar to be raised above the surrounding skin. Hypertrophic scars take the form of a red raised lump on the skin for lighter pigmented skin and the form of dark brown for darker pigmented skin. They usually occur within 4 to 8 weeks following wound infection or wound closure with excess tension and/or other traumatic skin injuries.{{cite journal |doi=10.2119/molmed.2009.00153 |pmid=20927486 |pmc=3022978 |year=2011 |last1=Gauglitz |first1=Gerd |journal=Molecular Medicine |volume=17 |issue=1–2 |pages=113–25 |last2=Korting |first2=Hans |title=Hypertrophic Scarring and Keloids: Pathomechanisms and Current and Emerging Treatment Strategies }}

{{Main|Keloid}}

Keloid scars are a more serious form of excessive scarring, because they can grow indefinitely into large, tumorous (although benign) neoplasms.

Hypertrophic scars are often distinguished from keloid scars by their lack of growth outside the original wound area, but this commonly taught distinction can lead to confusion.{{cite journal |vauthors=Roseborough IE, Grevious MA, Lee RC | title = Prevention and treatment of excessive dermal scarring | journal = J Natl Med Assoc | volume = 96 | issue = 1 | pages = 108–16 | date = January 2004 | pmid = 14746360 | pmc = 2594768 }}

Keloid scars can occur on anyone, but they are most common in dark-skinned people.Martini, Frederic H. (2006). Fundamentals of Anatomy & Physiology, Seventh Edition, p. 171. Benjamin Cummings, San Francisco. They can be caused by surgery, cuts, accident, acne or, sometimes, body piercings. In some people, keloid scars form spontaneously. Although they can be a cosmetic problem, keloid scars are only inert masses of collagen and therefore completely harmless and not cancerous. However, they can be itchy or painful in some individuals. They tend to be most common on the shoulders and chest. Hypertrophic scars and keloids tend to be more common in wounds closed by secondary intention. Surgical removal of keloid is risky and may exacerbate the condition and worsening of the keloid.

File:Atrophic scar of Ehlers Danlos syndrome.jpg

An atrophic scar takes the form of a sunken recess in the skin, which has a pitted appearance. These are caused when underlying structures supporting the skin, such as fat or muscle, are lost. This type of scarring is often associated with acne,{{cite journal | author = Goodman GJ | title = Postacne scarring: A review of its pathophysiology and treatment | journal = Dermatologic Surgery | volume = 26 | issue = 9 | pages = 857–871 | year = 2000 | pmid = 10971560 | doi=10.1046/j.1524-4725.2000.99232.x| s2cid = 25244676 }}{{cite journal |vauthors=Fabbrocini G, Annunziata MC, D'Arco V, De Vita V, Lodi G, Mauriello MC, Pastore F, Monfrecola G | title = Acne Scars: Pathogenesis, Classification and Treatment | journal = Dermatology Research and Practice | volume = 2010 | pages = 1–13 | year = 2010 | pmid = 20981308 | pmc = 2958495 | doi = 10.1155/2010/893080 | doi-access = free }} chickenpox, other diseases (especially Staphylococcus infection), surgery, certain insect and spider bites, or accidents. It can also be caused by a genetic connective tissue disorder, such as Ehlers–Danlos syndrome.{{Cite web|url=http://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-ehlers-danlos-syndromes#H35121407|title=Clinical manifestations and diagnosis of Ehlers-Danlos syndromes|website=www.uptodate.com|access-date=2017-06-15}}

{{Main|Stretch marks}}

Stretch marks (technically called striae) are also a form of scarring. These are caused when the skin is stretched rapidly (for instance during pregnancy,{{Cite journal |last1=Brennan |first1=Miriam |last2=Young |first2=Gavin |last3=Devane |first3=Declan |date=2012-11-14 |title=Topical preparations for preventing stretch marks in pregnancy |journal=The Cochrane Database of Systematic Reviews |volume=2012 |issue=11 |pages=CD000066 |doi=10.1002/14651858.CD000066.pub2 |issn=1469-493X |pmid=23152199|pmc=10001689 }} significant weight gain, or adolescent growth spurts),{{cite journal |vauthors=Elsaie ML, Baumann LS, Elsaaiee LT | title = Striae Distensae (Stretch Marks) and Different Modalities of Therapy: An Update | journal = Dermatologic Surgery | volume = 35 | issue = 4 | pages = 563–573 | year = 2009 | pmid = 19400881 | doi = 10.1111/j.1524-4725.2009.01094.x | s2cid = 7887237 }} or when skin is put under tension during the healing process (usually near joints). This type of scar usually improves in appearance after a few years.

Elevated corticosteroid levels are implicated in striae development.{{cite journal |vauthors=Hengge UR, Ruzicka T, Schwartz RA, Cork MJ | title = Adverse effects of topical glucocorticosteroids | journal = Journal of the American Academy of Dermatology | volume = 54 | issue = 1 | pages = 1–15 | year = 2006 | pmid = 16384751 | doi = 10.1016/j.jaad.2005.01.010 }}

Humans and other placental mammals have an umbilical scar (commonly referred to as a navel) which starts to heal when the umbilical cord is cut after birth. Egg-laying animals have an umbilical scar which, depending on the species, may remain visible for life or disappear within a few days after birth.{{cite news|url=https://www.smithsonianmag.com/arts-culture/what-types-of-animals-have-been-to-space-and-more-questions-from-our-readers-63029589/ |title=What Types of Animals Have Been to Space and More Questions From our Readers|work= Smithsonian |date=May 2012|access-date=25 November 2017}}{{cite web|url=https://www.fws.gov/southwest/es/arizona/Documents/Redbook/Flat-Tailed%20Horned%20Lizard%20RB.pdf |title=Flat-tailed horned lizard (Phrynosoma mcallii)|website= US Fish & Wildlife Service |access-date=25 November 2017}}

File:Key processes contributing to the quasi-neoplastic expression of keloid pathobiology.jpg

A scar is the product of the body's repair mechanism after tissue injury. If a wound heals quickly within two weeks with new formation of skin, minimal collagen will be deposited and no scar will form.{{Cite web| title = POST BURN SCAR RELATIVE TO RE-EPITHELIALIZATION| publisher = eplasty.com| year = 2011| url = http://eplasty.com/images/PDF/ManageBurnWound-part4.pdf| quote = Healing in 2 weeks – minimal to no scar; Healing in 3 weeks – minimal to no scar except in high risk scar formers;Healing in 4 weeks or more – hypertrophic in more than 50% of patients| access-date = 6 February 2016| archive-date = 5 October 2016| archive-url = https://web.archive.org/web/20161005230211/http://eplasty.com/images/PDF/ManageBurnWound-part4.pdf| url-status = dead}} When the extracellular matrix senses elevated mechanical stress loading, tissue will scar, and scars can be limited by stress shielding wounds.{{cite journal |doi=10.1038/jid.2011.212 |pmid=21776006 |title=Pushing Back: Wound Mechanotransduction in Repair and Regeneration |journal=Journal of Investigative Dermatology |volume=131 |issue=11 |pages=2186–2196 |year=2011 |last1=Wong |first1=Victor W. |last2=Akaishi |first2=Satoshi |last3=Longaker |first3=Michael T. |last4=Gurtner |first4=Geoffrey C. |doi-access=free }} Small full thickness wounds under 2mm reepithelize fast and heal scar free.{{cite journal |last1=Tam |first1=Joshua |last2=Wang |first2=Ying |last3=Vuong |first3=Linh N. |last4=Fisher |first4=Jeremy M. |last5=Farinelli |first5=William A. |last6=Anderson |first6=R. Rox |title=Reconstitution of full-thickness skin by microcolumn grafting |journal=Journal of Tissue Engineering and Regenerative Medicine |date=2016 |doi=10.1002/term.2174 |pmid=27296503 |pmc=5697650 |volume=11 |issue=10 |pages=2796–2805}} Deep second-degree burns heal with scarring and hair loss.{{cite web |last1=Kraft |first1=John |last2=Lynde |first2=Charles |title=Giving Burns the First, Second and Third Degree - Classification of burns |url=http://www.skincareguide.ca/articles/general_skin_care/gen_skin_care_art_3.html |access-date=31 January 2012 |publisher=skincareguide.ca |quote=Formation of a thick eschar, slow healing (>1month), Obvious scarring, hair loss.}} Sweat glands do not form in scar tissue, which impairs the regulation of body temperature.{{cite journal | vauthors = Fu XB, Sun TZ, Li XK, Sheng ZY | title = Morphological and distribution characteristics of sweat glands in hypertrophic scar and their possible effects on sweat gland regeneration | journal = Chinese Medical Journal | volume = 118 | issue = 3 | pages = 186–91 | date = February 2005 | pmid = 15740645 | url = http://cmj.yiigle.com/CN112154200503/1023825.htm | quote = In hypertrophic scar tissue, no sweet gland and hair follicle exist usually because of the dermal and epidermal damage in extensive thermal skin injury, thus impairing regulation of body temperature }} Elastic fibers are generally not detected in scar tissue younger than 3 months old.{{cite journal| title = Elastic fibers in scar tissue.| last = Roten SV1, Bhat S, Bhawan J.| date = February 1996| journal = Journal of Cutaneous Pathology| pmid=8720985| volume=23| issue = 1| pages=37–42| doi=10.1111/j.1600-0560.1996.tb00775.x| s2cid = 37823718}} In scars, rete pegs are lost; through a lack of rete pegs, scars tend to shear easier than normal tissue.{{cite book | last = Ira D. Papel | title = Facial Plastic and Reconstructive Surgery | publisher = Thieme Medical Publishers | edition = Third | date = 2011 | location = USA | pages = 7 | language = en | url = https://books.google.com/books?id=k6tyROvsZY4C&q=Facial+Plastic+and+Reconstructive+Surgery+7 | isbn = 9781588905154}}

The endometrium, the inner lining of the uterus, is the only adult tissue to undergo rapid cyclic shedding and regeneration without scarring, shedding and restoring roughly inside a 7-day window on a monthly basis.{{cite web| title = Endometrial repair| quote = Importantly, the endometrium is the only adult tissue to undergo rapid cyclic repair without scarring.| publisher = princehenrys.org| date = 18 September 2012 | url = http://www.princehenrys.org/endometrial-repair-menstruation| access-date = 30 June 2013| archive-url =https://web.archive.org/web/20090914010721/http://www.princehenrys.org/endometrial-repair-menstruation| url-status = dead| archive-date =2009-09-14}} All other adult tissues, upon rapid shedding or injury, can scar.

Prolonged inflammation, as well as the fibroblast proliferation, can occur. Redness that often follows an injury to the skin is not a scar and is generally not permanent (see wound healing). The time it takes for this redness to dissipate may, however, range from a few days to, in some serious and rare cases, a few years.{{cite journal | vauthors = Bayat A, McGrouther DA, Barton JJ, Ferguson MW | title = Skin scarring | journal = BMJ (Clinical Research Ed.) | publisher

= The BMJ | date = 11 January 2003 | volume = 326 | issue = 7380 | pages = 88–92 | doi = 10.1136/bmj.326.7380.88 | pmid = 12521975| pmc = 5398751 }}{{Citation needed|date=August 2010}}

Scars form differently based on the location of the injury on the body and the age of the person who was injured.{{Citation needed|date=August 2010}}

The worse the initial damage is, the worse the scar will generally be. {{Citation needed|date=August 2010}}

Skin scars occur when the dermis (the deep, thick layer of skin) is damaged. Most skin scars are flat and leave a trace of the original injury that caused them.{{Citation needed|date=August 2010}}

Wounds allowed to heal secondarily tend to scar worse than wounds from primary closure.{{Cite web | title = Practical Plastic Surgery for Nonsurgeons - Secondary Wound Closure - Scarring | quote = Wounds that are allowed to heal secondarily tend to have larger and more noticeable scars than the scars that results from primary closure. Secondary healing also has a greater tendency for hypertrophic scar/keloid formation. (page 86) | url = http://www.practicalplasticsurgery.org/docs/Practical_10.pdf | access-date = 2017-01-11 | archive-url = https://web.archive.org/web/20160826074024/http://www.practicalplasticsurgery.org/docs/Practical_10.pdf | archive-date = 2016-08-26}}

An injury does not become a scar until the wound has completely healed; this can take many months, or years in the worst pathological cases, such as keloids. To begin to patch the damage, a clot is created; this clot is the beginning process that results in a provisional matrix. In the process, the first layer is a provisional matrix and is not a scar. Over time, the wounded body tissue overexpresses collagen inside the provisional matrix to create a collagen matrix. This collagen overexpression continues and crosslinks the fiber arrangement inside the collagen matrix, making the collagen dense. This densely packed collagen, morphing into an inelastic whitish collagen scar wall, blocks off cell communication and regeneration; as a result, the new tissue generated will have a different texture and quality than the surrounding unwounded tissue. This prolonged collagen-producing process results in a fortuna scar.

The scarring is created by fibroblast proliferation, a process that begins with a reaction to the clot.{{cite journal |doi=10.1083/jcb.200704042 |pmid=18086923 |pmc=2140013 |title=Myofibroblast contraction activates latent TGF-β1 from the extracellular matrix |journal=The Journal of Cell Biology |volume=179 |issue=6 |pages=1311–1323 |year=2007 |last1=Wipff |first1=Pierre-Jean |last2=Rifkin |first2=Daniel B. |last3=Meister |first3=Jean-Jacques |last4=Hinz |first4=Boris }} To mend the damage, fibroblasts slowly form the collagen scar. The fibroblast proliferation is circular and cyclically, the fibroblast proliferation lays down thick, whitish collagen inside the provisional and collagen matrix, resulting in the abundant production of packed collagen on the fibers{{cite encyclopedia | title = Facts about fibroblast: scar tissue formation| quote = As part of the healing process, specialized cells called fibroblasts in adjacent areas of skin produce a fibrous connective tissue made up of collagen. The bundles formed by these whitish, rather inelastic fibres make up the bulk of the scar tissue...| encyclopedia = Britannica.com| url = http://www.britannica.com/facts/5/264152/fibroblast-as-discussed-in-scar-biology| access-date = 19 April 2010}} giving scars their uneven texture. Over time, the fibroblasts continue to crawl around the matrix, adjusting more fibers and, in the process, the scarring settles and becomes stiff. This fibroblast proliferation also contracts the tissue. In unwounded tissue, these fibers are not overexpressed with thick collagen and do not contract.

EPF and ENF fibroblasts have been genetically traced with the Engrailed-1 genetic marker. EPFs are the primary contributors to all fibrotic outcomes after wounding. ENFs do not contribute to fibrotic outcomes.{{Citation| last1 = Jiang| first1 = D| last2 = Rinkevich| first2 = Y | title = Scars or Regeneration?—Dermal Fibroblasts as Drivers of Diverse Skin Wound Responses| journal = International Journal of Molecular Sciences| year = 2020| volume = 21| issue = 2| page = 617| doi = 10.3390/ijms21020617| pmid = 31963533| pmc = 7014275| language = English| doi-access = free}}{{Citation| last = Rinkevich| first = Y| title = Skin fibrosis. Identification and isolation of a dermal lineage with intrinsic fibrogenic potential| journal = Science| year = 2015| volume = 348| issue = 6232| pages = aaa2151| doi = 10.1126/science.aaa2151| pmid = 25883361| pmc = 5088503| language = English}}

Mammalian wounds that involve the dermis of the skin heal by repair, not regeneration (except in 1st trimester inter-uterine wounds and in the regeneration of deer antlers). Full-thickness wounds heal by a combination of wound contracture and edge re-epitheliasation. Partial thickness wounds heal by edge re-epithelialisation and epidermal migration from adnexal structures (hair follicles, sweat glands and sebaceous glands). The site of keratinocyte stem cells remains unknown but stem cells are likely to reside in the basal layer of the epidermis and below the bulge area of hair follicles.

The fibroblast involved in scarring and contraction is the myofibroblast, which is a specialized contractile fibroblast. These cells express α-smooth muscle actin (α-SMA).{{cite journal |pmid=17586870 |url=https://www.o-wm.com/content/regenerative-healing-fetal-skin-a-review-literature?page=0,11 |year=2007 |last1=Wilgus |first1=T. A. |title=Regenerative healing in fetal skin: A review of the literature |journal=Ostomy/Wound Management |volume=53 |issue=6 |pages=16–31; quiz 32–3 }}

The myofibroblasts are absent in the first trimester in the embryonic stage where damage heals scar-free; in small incisional or excision wounds less than 2 mm that also heal without scarring; and in adult unwounded tissues where the fibroblast in itself is arrested; however, the myofibroblast is found in massive numbers in adult wound healing which heals with a scar.

The myofibroblasts make up a high proportion of the fibroblasts proliferating in the postembryonic wound at the onset of healing. In the rat model, for instance, myofibroblasts can constitute up to 70% of the fibroblasts,{{Cite web |author=Linge, Claire (Harrow, GB), Mackie, Ian Paul (Sheffield, GB) | title = Method of preventing or reducing scarring of human skin | quote = myofibroblasts become differentiated from other cells in the wound within a few days after the onset of healing, and in the rat model can reach a peak where about 70% of the fibroblastic cells present are of the myofibroblast phenotype. | publisher = freepatentsonline.com | url = http://www.freepatentsonline.com/y2005/0054608.html| access-date = 26 March 2010}} and is responsible for fibrosis on tissue.{{needs source|date=October 2024}} Generally, the myofibroblasts disappear from the wound within 30 days, but can remain in pathological cases in hypertrophy, such as keloids.{{Cite web |author=Linge, Claire (Harrow, GB), Mackie, Ian Paul (Sheffield, GB) | title = Method of preventing or reducing scarring of human skin| quote = These cells, which differentiate from the unwounded tissue cell type (fibroblasts), are responsible for laying down scar tissue. Indeed, myofibroblasts remain present in hypertrophic scars up to four years after the original wounding event. An in vitro assay was accordingly developed to identify actives which prevent or reduce myofibroblast formation and thus identify actives which are effective in reducing and/or preventing scar tissue formation. | publisher = freepatentsonline.com | url = http://www.freepatentsonline.com/y2005/0054608.html| access-date = 26 March 2010}}{{Cite web |author=Linge, Claire (Harrow, GB), Mackie, Ian Paul (Sheffield, GB) | title = Method of preventing or reducing scarring of human skin | quote = the number of myofibroblasts present in the forming scar tissue begins to reduce via apoptosis, until by about 30 days no myofibroblasts are obvious within the scar.| publisher = freepatentsonline.com | url = http://www.freepatentsonline.com/y2005/0054608.html| access-date = 26 March 2010}} Myofibroblasts have plasticity and in mice can be transformed into fat cells, instead of scar tissue, via the regeneration of hair follicles.{{cite journal | title = Regeneration of fat cells from myofibroblasts during wound healing | last = Plikus |display-authors=etal | date = 5 January 2017 | journal = Science | pmid=28059714 | doi=10.1126/science.aai8792 | volume=355 | issue = 6326 | pmc=5464786 | pages=748–752| bibcode = 2017Sci...355..748P }}{{cite journal | title = Repeal and Replace: Adipocyte Regeneration in Wound Repair. | last = Horsley, Watt | date = 6 April 2017 | journal = Cell Stem Cell | pmid=28388424 | doi=10.1016/j.stem.2017.03.015 | volume=20 | issue = 4 | pages=424–426| url = https://kclpure.kcl.ac.uk/portal/en/publications/repeal-and-replace-adipocyte-regeneration-in-wound-repair(bd32d20d-cd1f-4336-a20d-df4f2cda095b).html | type = Submitted manuscript | doi-access = free }}

Wounds under 2 millimeters generally do not scar, but larger wounds generally do scar. In 2011, it was found that mechanical stress can stimulate scarring and that stress shielding can reduce scarring in wounds. In 2021, it was found that using chemicals to manipulate fibroblasts to not sense mechanical stress brought scar-free healing. The scar-free healing also occurred when mechanical stress was placed onto a wound.{{cite web | url =https://www.statnews.com/2021/04/22/scientists-unlock-key-to-scar-free-skin-healing/ | title = In mouse experiments, scientists unlock the key to scar-free skin healing| last =Molteni | first =Megan | date =22 April 2021 | website = statnews.com| publisher = | access-date = 1 May 2021 | quote = }}

Early and effective treatment of acne scarring can prevent severe acne and the scarring that often follows.{{cite web | title = What is a Scar | url = http://www.aad.org/public/publications/pamphlets/cosmetic_scar.html | publisher = American Academy of Dermatology | quote = Early and effective acne treatment can prevent severe acne and the scarring that often follows | year = 2011 | access-date = 25 August 2011 | archive-date = 12 February 2011 | archive-url = https://web.archive.org/web/20110212180603/http://www.aad.org/public/publications/pamphlets/cosmetic_scar.html | url-status = dead }} In 2004, no prescription drugs for the treatment or prevention of scars were available.{{cite journal |vauthors=Ferguson MW, O'Kane S | title = Scar-free healing: from embryonic mechanisms to adult therapeutic intervention | journal = Philos. Trans. R. Soc. Lond. B Biol. Sci. | volume = 359 | issue = 1445 | pages = 839–50 | date = May 2004 | pmid = 15293811 | pmc = 1693363 | doi = 10.1098/rstb.2004.1475 }}

Chemical peels are chemicals which destroy the epidermis in a controlled manner, leading to exfoliation and the alleviation of certain skin conditions, including superficial acne scars.{{cite journal | author = Khunger N | title = Standard guidelines of care for acne surgery | journal = Indian Journal of Dermatology, Venereology and Leprology | volume = 74 Suppl | pages = S28–36 | date = January 2008 | pmid = 18688101 | url = http://www.ijdvl.com/article.asp?issn=0378-6323;year=2008;volume=74;issue=7;spage=28;epage=36;aulast=Khunger }} Various chemicals can be used depending upon the depth of the peel, and caution should be used, particularly for dark-skinned individuals and those individuals susceptible to keloid formation or with active infections.{{cite journal | author = Khunger N | title = Standard guidelines of care for chemical peels | journal = Indian Journal of Dermatology, Venereology and Leprology | volume = 74 Suppl | pages = S5–12 | date = January 2008 | pmid = 18688104 | url = http://www.ijdvl.com/article.asp?issn=0378-6323;year=2008;volume=74;issue=7;spage=5;epage=12;aulast=Khunger }}

Filler injections of collagen can be used to raise atrophic scars to the level of surrounding skin.{{cite journal |vauthors=Cooper JS, Lee BT | title = Treatment of facial scarring: lasers, filler, and nonoperative techniques | journal = Facial Plastic Surgery | volume = 25 | issue = 5 | pages = 311–5 | date = December 2009 | pmid = 20024872 | doi = 10.1055/s-0029-1243079 | s2cid = 260136591 }} Risks vary based upon the filler used, and can include further disfigurement and allergic reaction.{{cite journal |vauthors=Lemperle G, Rullan PP, Gauthier-Hazan N | title = Avoiding and treating dermal filler complications | journal = Plastic and Reconstructive Surgery | volume = 118 | issue = 3 Suppl | pages = 92S–107S | date = September 2006 | pmid = 16936549 | doi = 10.1097/01.prs.0000234672.69287.77 | s2cid = 32471639 | url = http://www.escholarship.org/uc/item/4t0019d6 }}

Nonablative lasers, such as the 585 nm pulsed dye laser, 1064 nm and 1320 nm Nd:YAG, or the 1540 nm Er:Glass are used as laser therapy for hypertrophic scars and keloids.{{cite journal |vauthors=Elsaie ML, Choudhary S |title=Lasers for scars: A review and evidence-based appraisal |journal=Journal of Drugs in Dermatology |volume=9 |issue=11 |pages=1355–62 |date=November 2010 |pmid=21061757}} There is tentative evidence for burn scars that they improve the appearance.{{cite journal |last1=Willows |first1=B.M. |last2=Ilyas |first2=M. |last3=Sharma |first3=A. |title=Laser in the management of burn scars |journal=Burns |date=4 August 2017 |doi=10.1016/j.burns.2017.07.001 |pmid=28784339 |volume=43 |issue=7 |pages=1379–1389}}{{cite journal |last1=Friedstat |first1=JS |last2=Hultman |first2=CS |title=Hypertrophic burn scar management: what does the evidence show? A systematic review of randomized controlled trials. |journal=Annals of Plastic Surgery |date=2014 |volume=72 |issue=6 |pages=S198–201 |doi=10.1097/SAP.0000000000000103 |pmid=24835874|s2cid=47573176 }}

Ablative lasers such as the carbon dioxide laser (CO{{sub|2}}) or Er:YAG offer the best results for atrophic and acne scars.{{cite journal |vauthors=Khatri KA, Mahoney DL, McCartney MJ |title=Laser scar revision: A review |journal=Journal of Cosmetic and Laser Therapy |volume=13 |issue=2 |pages=54–62 |date=April 2011 |pmid=21401378 |doi=10.3109/14764172.2011.564625|s2cid=11520661 }} Like dermabrasion, ablative lasers work by removing the epidermis.{{Citation |last1=Verma |first1=Neil |title=Ablative Laser Resurfacing |date=2022 |url=http://www.ncbi.nlm.nih.gov/books/NBK557474/ |work=StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=32491406 |access-date=2022-07-21 |last2=Yumeen |first2=Sara |last3=Raggio |first3=Blake S.}}{{Cite web |title=Laser resurfacing |url=https://www.mayoclinic.org/tests-procedures/laser-resurfacing/about/pac-20385114 |access-date=2022-07-21 |website=Mayo Clinic |language=en}} Healing times for ablative therapy are much longer and the risk profile is greater compared to nonablative therapy; however, nonablative therapy offers only minor improvements in cosmetic appearance of atrophic and acne scars.

Low-dose, superficial radiotherapy is sometimes used to prevent recurrence of severe keloid and hypertrophic scarring. It is thought to be effective despite a lack of clinical trials, but only used in extreme cases due to the perceived risk of long-term side effects.{{cite journal |vauthors=Ogawa R, Yoshitatsu S, Yoshida K, Miyashita T | title = Is radiation therapy for keloids acceptable? The risk of radiation-induced carcinogenesis | journal = Plastic and Reconstructive Surgery | volume = 124 | issue = 4 | pages = 1196–201 | date = October 2009 | pmid = 19935303 | doi = 10.1097/PRS.0b013e3181b5a3ae | s2cid = 25294698 }}

Silicone scar treatments are commonly used in preventing scar formation and improving existing scar appearance.{{cite journal |vauthors=Stavrou D, Weissman O, Winkler E, Yankelson L, Millet E, Mushin OP, Liran A, Haik J | title = Silicone-based scar therapy: a review of the literature | journal = Aesthetic Plastic Surgery | volume = 34 | issue = 5 | pages = 646–51 | date = October 2010 | pmid = 20354695 | doi = 10.1007/s00266-010-9496-8 | s2cid = 43820233 }} A meta-study by the Cochrane collaboration found weak evidence that silicone gel sheeting helps prevent scarring. However, the studies examining it were of poor quality and susceptible to bias.{{cite journal|last1=O'Brien|first1=L|last2=Jones|first2=DJ|title=Silicone gel sheeting for preventing and treating hypertrophic and keloid scars.|journal=The Cochrane Database of Systematic Reviews|date=12 September 2013|volume=9|issue=9|pages=CD003826|pmid=24030657|doi=10.1002/14651858.CD003826.pub3|pmc=7156908}}

Pressure dressings are commonly used in managing burn and hypertrophic scars, although supporting evidence is lacking.{{cite journal |vauthors=Shih R, Waltzman J, Evans GR | title = Review of over-the-counter topical scar treatment products | journal = Plastic and Reconstructive Surgery | volume = 119 | issue = 3 | pages = 1091–5 | date = March 2007 | pmid = 17312518 | doi = 10.1097/01.prs.0000255814.75012.35 | s2cid = 2756632 }} Care providers commonly report improvements, however, and pressure therapy has been effective in treating ear keloids. The general acceptance of the treatment as effective may prevent it from being further studied in clinical trials.

Verapamil, a type of calcium channel blocker, is considered a candidate drug for the treatment of hypertrophic scars. A study conducted by the Catholic University of Korea concluded that verapamil-releasing silicone gel is effective and is a superior alternative to the conventional silicone gel where decreased median SEI, fibroblast count, and collagen density in all verapamil-added treatment groups were observed.{{Cite journal |last1=Choi |first1=Jangyoun |last2=Han |first2=Yu Na |last3=Rha |first3=Eun Young |last4=Kang |first4=Hwi Ju |last5=Kim |first5=Ki Joo |last6=Park |first6=Il Kyu |last7=Kim |first7=Hyun-Jung |last8=Rhie |first8=Jong Won |date=2021-03-17 |title=Verapamil-containing silicone gel reduces scar hypertrophy |journal=International Wound Journal |volume=18 |issue=5 |pages=647–656 |doi=10.1111/iwj.13566 |issn=1742-4801 |pmc=8450805 |pmid=33733593}}{{rp|647–656}} Gross morphologic features suggested that the combination of verapamil and silicone improves the overall quality of hypertrophic scars by reducing scar height and redness. This was verified with quantifiable histomorphometric parameters; however, oral verapamil is not a good choice because of its effect of lowering blood pressure. Intralesional injection of verapamil is also suboptimal because of the required frequency for injections. Topical silicone gel combined with verapamil does not lead to systemic hypotension, is convenient to apply, and shows enhanced results.{{rp|647–656}}

A long-term course of corticosteroid injections into the scar may help flatten and soften the appearance of keloid or hypertrophic scars.{{cite journal |vauthors=Roques C, Téot L | title = The Use of Corticosteroids to Treat Keloids: A Review | journal = The International Journal of Lower Extremity Wounds | volume = 7 | issue = 3 | pages = 137–145 | year = 2008 | pmid = 18611924 | doi = 10.1177/1534734608320786 | s2cid = 9577277 }}

Topical steroids are ineffective.Jenkins M, Alexander JW, MacMillan BG, Waymack JP, Kopcha R. Failure of topical steroids and vitamin E to reduce postoperative scar formation following reconstructive surgery. J Burn Care Rehabil. 1986 Jul–Aug;7(4):309–312. However, clobetasol propionate can be used as an alternative treatment for keloid scars.{{Cite journal | title=A Randomized, Single-Blind Trial of Clobetasol Propionate 0.05% Cream Under Silicone Dressing Occlusion Versus Intra-Lesional Triamcinolone for Treatment of Keloid | journal=Clinical Drug Investigation | volume=37 | issue=3 | pages=295–301 | date=2016-11-25 | pmid=27888448 | last1=Nor | first1=N. M. | last2=Ismail | first2=R. | last3=Jamil | first3=A. | last4=Shah | first4=S. A. | last5=Imran | first5=F. H. | doi=10.1007/s40261-016-0484-x | s2cid=33614354 }}

Topical steroid applied immediately after fractionated {{CO2}} laser treatment is however very effective (and more efficacious than laser treatment alone) and has shown benefit in numerous clinical studies.

File:scar revision.jpg (left), and photo one day after scar revision surgery: The area around sutures is still swollen from surgery.]]

Scar revision is a process of cutting the scar tissue out. After the excision, the new wound is usually closed up to heal by primary intention, instead of secondary intention. Deeper cuts need a multilayered closure to heal optimally, otherwise depressed or dented scars can result.{{Cite web | title = Scar revisions | quote = Deep cuts need multi-layered closure to heal optimally; otherwise, depressed or dented scars can result | url = http://www.haplasticsurgery.com/scar-revision-surgery-dallas-texas.html | access-date = 16 October 2010 | archive-url = https://web.archive.org/web/20120119050557/http://www.haplasticsurgery.com/scar-revision-surgery-dallas-texas.html | archive-date = 19 January 2012 | url-status = dead | df = dmy-all }}

Surgical excision of hypertrophic or keloid scars is often associated to other methods, such as pressotherapy or silicone gel sheeting. Lone excision of keloid scars, however, shows a recurrence rate close to 45%. A clinical study is currently ongoing to assess the benefits of a treatment combining surgery and laser-assisted healing in hypertrophic or keloid scars.

Subcision is a process used to treat deep rolling scars left behind by acne or other skin diseases. It is also used to lessen the appearance of severe glabella lines, though its effectiveness in this application is debatable. Essentially the process involves separating the skin tissue in the affected area from the deeper scar tissue. This allows the blood to pool under the affected area, eventually causing the deep rolling scar to level off with the rest of the skin area. Once the skin has leveled, treatments such as laser resurfacing, microdermabrasion or chemical peels can be used to smooth out the scarred tissue.{{Cite web|date=2014-09-17|title=Chemical peels vs laser peels vs microdermabrasion: which one is right for you?|url=https://www.bclaserandskincare.com/2014/09/lasers-chemical-peels/|access-date=2021-06-24|website=Beautiful Canadian Laser and Skincare Clinic|language=en-CA}}

Research shows the use of vitamin E and onion extract (sold as Mederma) as treatments for scars is ineffective. Vitamin E causes contact dermatitis in up to 33% of users and in some cases it may worsen scar appearance and could cause minor skin irritations, but Vitamin C and some of its esters fade the dark pigment associated with some scars.Farris PK. Topical vitamin C: a useful agent for treating photoaging and other dermatologic conditions. Although many people claim that vitamin therapy does in fact help. Dermatol Surg 2005;31:814-818.

• Cosmetics; Medical makeup can temporarily conceal scars.{{Cite journal|title = Medical Makeup for Concealing Facial Scars|url = http://pubs.bli.uci.edu/sites/default/files/publications/s-0032-1325647.pdf|journal = Facial Plastic Surgery|date = 2012-10-01|pages = 536–540|volume = 28|issue = 5|doi = 10.1055/s-0032-1325647|language = en|first1 = Donna|last1 = Mee|first2 = Brian|last2 = Wong|pmid = 23027221|s2cid = 23900892|access-date = 30 January 2016|archive-date = 5 October 2016|archive-url = https://web.archive.org/web/20161005230125/http://pubs.bli.uci.edu/sites/default/files/publications/s-0032-1325647.pdf|url-status = dead}} This is most commonly used for facial scars.
• Dermabrasion involves the removal of the surface of the skin with special equipment, and usually involves a local anaesthetic.
• A 2012 literature review found weak evidence that massage was efficacious in scar management. Any beneficial effect appeared to be greater in wounds created by surgical incision than for traumatic or burn wounds.{{cite journal|last1=Shin|first1=Thuzar M.|last2=Bordeaux|first2=Jeremy S.|title=The Role of Massage in Scar Management: A Literature Review|journal=Dermatologic Surgery|volume=38|issue=3|year=2012|pages=414–423|issn=1076-0512|doi=10.1111/j.1524-4725.2011.02201.x|pmid=22093081|s2cid=1018590}} A 2022 scoping review covering twenty-five studies of 1515 participants reported that all studies reviewed reported favorable outcomes for scar massage, but that "while there may be benefits to scar massage in reducing pain, increasing movement and improving scar characteristics", there was a lack of "consistent research methods, intervention protocols and outcome measures".{{cite journal | last1=Scott | first1=Helen C. | last2=Stockdale | first2=Claire | last3=Robinson | first3=Andrea | last4=Robinson | first4=Luke S | last5=Brown | first5=Ted | title=Is massage an effective intervention in the management of post-operative scarring? A scoping review | journal=Journal of Hand Therapy | volume=35 | issue=2 | date=2022 | doi=10.1016/j.jht.2022.01.004 | pages=186–199| pmid=35227556 }}
• Microneedling{{cite journal|last1=Cohen|first1=BE|last2=Elbuluk|first2=N|title=Microneedling in skin of color: A review of uses and efficacy.|journal=Journal of the American Academy of Dermatology|date=February 2016|volume=74|issue=2|pages=348–55|pmid=26549251|doi=10.1016/j.jaad.2015.09.024}}

{{main|Scarification}}

The permanence of scarring has led to its intentional use as a form of body art within some cultures and subcultures. These forms of ritual and non-ritual scarring practices can be found in many groups and cultures around the world.

First attested in English in the late 14th century, the word scar derives from a conflation of Old French escharre, from Late Latin eschara,[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Deschara eschara],

Charlton T. Lewis, Charles Short, A Latin Dictionary, on Perseus which is the Latinisation of the Greek ἐσχάρα (eskhara), meaning "hearth, fireplace", but in medicine "scab, eschar on a wound caused by burning or otherwise",[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3De%29sxa%2Fra ἐσχάρα], Henry George Liddell, Robert Scott, A Greek-English Lexicon, on perseus[http://www.etymonline.com/index.php?term=scar Online Etymology Dictionary] and Middle English skar ("cut, crack, incision"), which is from Old Norse skarð ("notch, gap"). The conflation helped to form the English meaning. Compare the place name Scarborough for evolution of skarð to scar.

{{Further|Scar free healing}}

Research, before 2009, focused on scar improvements with research into molecular mechanisms. Treatments involving molecular mechanisms including avotermin,{{cite journal |doi=10.1016/S0140-6736(09)60322-6 |pmid=19362676 |title=Prophylactic administration of avotermin for improvement of skin scarring: Three double-blind, placebo-controlled, phase I/II studies |journal=The Lancet |volume=373 |issue=9671 |pages=1264–1274 |year=2009 |last1=Ferguson |first1=Mark WJ |last2=Duncan |first2=Jonathan |last3=Bond |first3=Jeremy |last4=Bush |first4=James |last5=Durani |first5=Piyush |last6=So |first6=Karen |last7=Taylor |first7=Lisa |last8=Chantrey |first8=Jonquille |last9=Mason |first9=Tracey |last10=James |first10=Gaynor |last11=Laverty |first11=Hugh |last12=Occleston |first12=Nick L. |last13=Sattar |first13=Abdul |last14=Ludlow |first14=Anna |last15=O'Kane |first15=Sharon |s2cid=35671002 }}{{cite journal |doi=10.1016/S0140-6736(09)60705-4 |pmid=19362658 |title=Wound healing: From embryos to adults and back again |journal=The Lancet |volume=373 |issue=9671 |pages=1226–1228 |year=2009 |last1=Tredget |first1=Edward E. |last2=Ding |first2=Jie |s2cid=10236414 }} ribosomal s6 kinase (RSK),{{cite news |title=Liver damage 'could be reversed' |url=http://news.bbc.co.uk/2/hi/health/7152415.stm |date=27 December 2007 |work=BBC News |access-date=1 January 2008}} and osteopontin[http://jem.rupress.org/cgi/content/abstract/205/1/43 'Molecular mechanisms linking wound inflammation and fibrosis: knockdown of osteopontin leads to rapid repair and reduced scarring']{{cite news| url=http://news.bbc.co.uk/2/hi/health/7199897.stm | work=BBC News | title=Gel 'to speed up wound healing' | date=22 January 2008 | access-date=23 May 2010}} were investigated at the time. After successful phase I/II trials, human recombinant TGF-β3 (avotermin, planned trade name Juvista) failed in Phase III trials.[http://www.thepharmaletter.com/file/102058/renovo-shares-plummet-75-as-scar-revision-product-juvista-fails-to-meet-study-endpoints.html Renovo shares plummet 75% as scar revision product Juvista fails to meet study endpoints], 14 February 2011

In 2011, the scientific literature highlighted stress shielding a fresh wound through the wound healing process, brings significant scar improvement and smaller scars.{{cite journal | title = Updated Scar Management Practical Guidelines: Non-invasive and invasive measures | last = Monstrey | first = Stan | date = 1 August 2014 | journal = Journal of Plastic, Reconstructive & Aesthetic Surgery | volume = 67 | issue = 8 | pages = 1017–25 | doi = 10.1016/j.bjps.2014.04.011 | pmid = 24888226 | doi-access = free | hdl = 11577/2834337 | hdl-access = free }}

By 2016, skin had been regenerated in vivo and in vitro. and scar-free healing had been operationalized and induced by four main regeneration techniques: by instrument, by materials, by drugs, and by in vitro 3-D printing. In 2018, a silk-derived sericin hydrogel dressing was undergoing research, the material was shown to prevent scar formation.{{cite news |last=Dey |first=Becky |url=https://www.chemistryworld.com/news/silk-route-to-scar-free-skin/3009682.article |title=Silk route to scar-free skin |work=Chemistry World |date=2018-10-29 |access-date=2019-06-18 }} By 2021, more people were paying attention to the possibility of scar revision and new technologies.{{cite journal | last = Tang | first = Xuwen | author-link = | title = Micro-compound tissue grafting for repairing linear scars | journal = Chinese Journal of Plastic and Reconstructive Surgery | volume = 3 | issue = 4 | pages = 202–203 | location = China | date = 1 December 2021 | doi = 10.1016/j.cjprs.2021.11.002 | s2cid = 244827273 | language = English | issn = 2096-6911 | doi-access = free }}

In 2021, researchers found that, verteporfin, an FDA-approved drug for eye disease, could enable scar-free healing in mice. According to the study, the drug works by blocking mechanical stress signals in fibroblast cells.{{Cite web |last=Vaughan |first=Christopher |date=22 April 2021 |title=Researchers find drug that enables healing without scarring |url=https://med.stanford.edu/news/all-news/2021/04/drug-enables-healing-without-scarring.html |access-date=13 September 2024 |website=Stanford Medicine |language=en-US}}{{Cite journal |last1=Mascharak |first1=Shamik |last2=desJardins-Park |first2=Heather E. |last3=Davitt |first3=Michael F. |last4=Griffin |first4=Michelle |last5=Borrelli |first5=Mimi R. |last6=Moore |first6=Alessandra L. |last7=Chen |first7=Kellen |last8=Duoto |first8=Bryan |last9=Chinta |first9=Malini |last10=Foster |first10=Deshka S. |last11=Shen |first11=Abra H. |last12=Januszyk |first12=Michael |last13=Kwon |first13=Sun Hyung |last14=Wernig |first14=Gerlinde |last15=Wan |first15=Derrick C. |date=2021-04-23 |title=Preventing Engrailed-1 activation in fibroblasts yields wound regeneration without scarring |journal=Science |language=en |volume=372 |issue=6540 |doi=10.1126/science.aba2374 |issn=0036-8075 |pmc=9008875 |pmid=33888614}}{{Cite web |last=Kolata |first=Gina |date=22 April 2021 |title=Imagine, Surgery Without a Scar |url=https://www.nytimes.com/2021/04/22/health/surgery-scar.html |archive-url=https://archive.today/20231209113757/https://www.nytimes.com/2021/04/22/health/surgery-scar.html |archive-date=9 December 2023 |access-date=13 September 2024 |website=The New York Times}}

• Wound healing
• Regeneration in humans

{{reflist|25em}}

{{commons category}}

• [https://web.archive.org/web/20170921235712/http://www.webmd.com/skin-problems-and-treatments/skin-scars-directory WebMd.com: Skin Scars Directory] (archived 21 September 2017)
• [http://www.aad.org/public/kids/skin/scars/ American Academy of Dermatology: What is a scar?] {{Webarchive|url=https://web.archive.org/web/20181121093841/https://www.aad.org/public/kids/skin/scars |date=21 November 2018 }}

{{Medical resources

| DiseasesDB =

| ICD10 = L90.5

| OMIM =

| MedlinePlus =

| eMedicineSubj =

| eMedicineTopic =

| MeshID = D002921

}}

{{Wound healing}}

{{Cutaneous keratosis, ulcer, atrophy, and necrobiosis}}

{{Connective tissue}}

{{Authority control}}

Category:Healing

Category:Skin conditions resulting from physical factors