1Harvard Medical School, Harvard University, Boston, MA, USA
2Department of Dermatology, Brigham and Women’s Hospital, Boston, MA, USA
3King Saud bin Abdulaziz University for Health Sciences, Jeddah, Saudi Arabia
4King Abdullah International Medical Research Center, Jeddah, Saudi Arabia
5Division of Dermatology, Department of Medicine, Ministry of the National Guard-Health Affairs, Jeddah, Saudi Arabia
6Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
7Farwaniya Hospital, Kuwait City, Kuwait
8Division of Dermatology, University of Toronto, Toronto, ON, Canada
Conflict of interest:
The authors have no conflicts to disclose.
Acne vulgaris is a troubling skin disease known to have both physiologic and psychological effects on patients. Acne scars, a frequent complication, can further impact patients’ quality of life. Scars result from an impairment in the healing process. Acne scars can be categorized as follows: atrophic scars (including ice pick, rolling, boxcar subtypes) and trophic (including hypertrophic and keloid scars), the latter being less common. Though various treatment approaches have been suggested, there is a lack of high‐quality evidence on effective, type-specific acne scar approaches. Herein, we aim to review the current evidence for treating various acne scars.
acne scars, atrophic, ice pick, rolling, boxcar, hypertrophic, keloid
Acne vulgaris is the most common skin disease affecting adolescents and adults.1 Studies have demonstrated that about 99% of the population has had acne at some point in their lives, varying in degree of severity, duration, and age of onset.1
The psychological impact of acne is well known. Acne can have social and psychological consequences beyond the apparent visual deformity. This common condition has been linked to stress, anxiety, depression, and suicidal ideation.2 Singam et al. reported that severe acne is associated with comorbid mental health disorders in 25% of acne patients, including anxiety, adjustment, personality, and substance use disorders.3 Acne has also been associated with reduced academic achievement and social difficulties.1
Acne scars are a frequent complication that results from damage to the skin during the healing process of lesions, with studies indicating that 50% of those suffering from acne may develop scars.4 Increased risk of scarring is associated with severe disease, time between acne onset and first effective treatment, relapsing acne, and males.4 Herein, we discuss different types of acne scars and present an updated review on type-specific management approaches.
Acne scars can be classified as atrophic, hypertrophic, or keloidal. The morphology of these scars is summarized in Figure 1. Atrophic acne scars are further subdivided into three subtypes: ice pick, rolling, and boxcar.
The management approach for treating acne scars should be type-specific given the differences in underlying pathophysiology. Treatment options for each type of scar are summarized in Table 1.
Table 1. Clinical presentation and treatment options of acne scars
Table 1. Clinical presentation and treatment options of acne scars
Ice Pick Scars
Ice pick scars extend vertically into the deep dermis or subcutaneous tissue. They are narrow (<2 mm) at the surface and taper as they extend into the deep dermis. Conventional skin resurfacing treatment options may not be adequate due to their depth. Punch excision can be used to treat ice pick scars. Though this method forms a new scar, it is generally less visible than the original ice pick scar.5 The punch excision can be followed by a resurfacing procedure after 4 to 6 weeks, which can further improve the scar’s appearance. Notably, laser skin resurfacing can be safely and effectively performed on the same day that the punch scar is created.6
Another treatment option for ice pick scars is chemical reconstruction of skin scars (CROSS) using high concentrations of trichloroacetic acid (TCA) to induce skin regeneration. TCA is strictly applied to localized areas; the controlled application results in a shorter recovery time compared to medium or deep chemical peels. The degree of clinical improvement is dependent on the total number of treatments.7
TCA CROSS can also be used in darker skin types. In a study evaluating the efficacy and safety of CROSS technique, researchers used 100% TCA to treat ice pick scars in patients with Fitzpatrick phototypes IV and V. Nearly 75% of participants experienced excellent improvement in the appearance of their scars after 4 sessions at 2-week intervals.8
Radiofrequency (RF) is another option for treating ice pick scars. RF devices use electromagnetic radiation to produce an electric current that delivers heat to the dermis, which in turn causes neocollagenesis and skin contraction. This technique is considered both safe and efficacious, offering minimal downtime and adverse events.9 Additionally, RF is a safe procedure in skin of color (SOC) as it does not directly target pigment.
Several studies have demonstrated the effectiveness of RF in the management of ice pick scars. Ramesh et al. reported that fractional bipolar RF (FRF) achieved good results in 73% patients after 4 sessions. Patients with ice pick scars exhibited a better response than those with rolling and boxcar scars.10
Conversely, Peterson et al. found that 15 patients diagnosed with rolling and boxcar scars responded better to 5 sessions of a combination of RF and FRF than patients with ice pick scars.11
Another mode of therapy for ice pick scars is resurfacing lasers. This treatment modality has yielded only mild-to-moderate efficacy for ice pick scars, compared to other subtypes. Sardana et al. reported that treatment with a 1,540 nm fractional nonablative laser improved scar appearance for only 25.9% of patients with ice pick scars, compared with 52.9% and 43.1% improvement in boxcar and rolling scars, respectively.12
Combining ablative fractional carbon dioxide (CO2) laser with platelet-rich plasma (PRP) injections represents an innovative approach. PRP involves preparing and administering the patient’s own concentrated platelets in plasma containing variable growth factors and cytokines that promote wound healing. A recent meta-analysis investigated the efficacy and safety of combining fractional CO2 laser with PRP for managing atrophic acne scars. It was concluded that the dual approach led to enhanced outcomes compared to using ablative fractional CO2 laser alone. Specifically, the combination resulted in clinical improvement, increased patient satisfaction, and accelerated recovery after laser damage. However, further research is needed to evaluate the efficacy of PRP for acne scars.13 PRP can also be combined with microneedling to treat any atrophic acne scars.
Rolling scars result from dermal tethering of abnormal fibrous bands that produce skin indentation. The scars are 4-5 mm wide and are sloped, with shallow borders.
Rolling scars can be best managed surgically with subcision, which involves the use of a tri-beveled hypodermic needle to free the tethering subdermal fibrous bands. Al-Dhalimi et. al showed
that subcision downgraded the severity of rolling acne scars from moderate-to-severe grade to mild grade in 53% of patients, with minimal side effects.14 The subcision was done once and repeated every 6 weeks, as required.
Subcision has been combined with the application of soft tissue fillers and non-ablative laser to improve the appearance of rolling scars. Hyaluronic acid fillers can expand the volume of tissue in these scars and encourage collagen production. Sapra et al. assessed the management of rolling scars with poly-L-lactic acid (PLLA) in 22 patients and demonstrated that after 3 to 4 treatments at 4-week intervals with PLLA, 54.4% of patients exhibited excellent results.15 A controlled and blinded study was performed on 147 patients with rolling acne scars to evaluate the effectiveness of 1 injection of polymethylmethacrylate (PMMA) filler. Neary 65% of patients demonstrated good improvement, compared to 33% of control subjects.16
Microdermabrasion and dermabrasion are physical ablating modalities used to manage rolling scars. Microdermabrasion is more superficial whereas dermabrasion reaches the deeper papillary dermis layer. The procedures promote a wound healing response and new collagen formation. Eventually, dermabrasion treatment results in smoother and uniform appearance of the scar.17 Microdermabrasion received at weekly intervals appears to be safe in SOC.18
Microneedling is another beneficial option for managing rolling scars. Microneedling involves creating small wounds in the dermis to activate a cascade of growth factors and eventually stimulate collagen production.19 Microneedling can be effective in managing rolling scars for darker-skinned patients due to the low risk of hyperpigmentation compared to fractional nonablative laser therapy.7
RF can also be used safely and effectively to manage rolling acne scars with minimum adverse effects and limited downtime.7
Non-ablative lasers can also be used to manage rolling scars. Their mechanism of action involves targeting tissues in the dermis for selective photothermolysis to encourage collagen and
dermal remodeling, thereby improving the appearance of scars.20
Boxcar scars are broad, round-to-oval or rectangular box-like depressions with sharply defined edges. Punch excision and punch elevation are two excellent techniques for the treatment of boxcar scars, but there is still a paucity in literature evaluating their effectiveness for improving acne scarring.7 For punch elevation, the punch biopsy tool is used to fragment the deeper aspect of the scar without removing any epidermis or dermis.
Dermabrasion can be an effective option for managing boxcar scars, but it is a painful procedure that requires local or general anesthesia and the healing time may extend to several weeks, with significant postoperative discomfort.21 Microneedling RF is another useful technique that can be employed to manage atrophic boxcar scars.11 RF does not directly target melanin and can thus be safely used in SOC.
Subcision is moderately effective for managing boxcar scars, but it can be combined with other resurfacing procedures such as cosmetic fillers and non-ablative lasers to achieve better results.20 Chemical peeling with TCA can be used to manage hard-to-treat boxcar scars.22 Finally, laser skin resurfacing can deliver excellent results for managing acne scars. One study demonstrated that use of a high-energy pulsed CO2 laser provided 75% improvement in atrophic facial scars, including boxcar scars.23 Ablative lasers, such as CO2 and erbium-doped yttrium aluminum garnet (Er:YAG), should be used with caution when treating atrophic scars in SOC. The risk of postinflammatory hyperpigmentation (PIH) appears to be decreased with Er:YAG. Post ablative laser PIH may last for 5 weeks and can be treated with a topical depigmenting agent such as hydroquinone 4% or combination topicals (retinoid, hydroquinone and corticosteroid).24,25
Hypertrophic Scars and Keloids
Hypertrophic scars and keloids are more severe types of acne scars. They are less common compared to atrophic acne scars, but can be difficult to treat. Typically, hypertrophic scars appear as pink, raised lesions that persist within the borders of the original site of injury.26 Keloids present as reddish-purple scars that frequently extend beyond the borders of the original site of injury.27 From a pathophysiological perspective, hypertrophic and keloidal scars demonstrate excessive expression of collagen with reduced collagenase activity.28
Intralesional corticosteroid injections represent the mainstay of treatment for hypertrophic and keloid scars. However, multiple treatment approaches can be used simultaneously to maximize the potential for success and minimize adverse effects.29 For example, intralesional corticosteroid injections can be accompanied by 5-fluorouracil (5-FU) to reduce the risk for hypopigmentation, skin atrophy, telangiectasias, rebound scars, ineffectiveness, and injection site pain.28
Laser resurfacing can be considered for managing hypertrophic and keloid acne scars. Specifically, pulsed dye laser is an excellent option to consider.30 Thick keloid or hypertrophic scars can benefit from using a combination of pulsed dye laser and intralesional corticosteroid injections along with 5-FU.31 In fact, this combination seems to be the most promising, currently available therapy for keloids.32
Another effective non-surgical method for managing small hypertrophic acne scars is cryotherapy, which can also be combined with intralesional triamcinolone to maximize effectiveness.33
Surgical excision can be used in combination with other approaches including radiotherapy, interferon, bleomycin, cryotherapy, or corticoids to optimize the efficacy of the management protocol.34 Surgical excision may be needed when acne scars are disabling, but in some cases laser and light-based therapies may be preferential.35
Large keloid scars have been effectively managed with surgical excision followed by radiation using brachytherapy. This is better tolerated and enables delivery of high radiation doses to a focused area, with decreased side effects, in comparison to traditional external beam radiation.36 Intralesional injection of interferon and bleomycin are additional options for managing keloid and hypertrophic scars. These treatments work to increase collagen breakdown and inhibit collagen synthesis, respectively. Both therapies can enhance the scar’s appearance.37,38
The post-excision recurrence of keloids has shown to decrease with daily application of topical imiquimod 5% cream for 8 weeks.39,40
The management of acne scars often requires a combination of different treatment options. An understanding of each scar type and formulating a case-specific approach are required to achieve optimal outcomes.
- Jordan R, Cummins C, Burls A. Laser resurfacing of the skin for the improvement of facial acne scarring: a systematic review of the evidence. Br J Dermatol. 2000 Mar;142(3):413-23.
- Sereflican B, Tuman TC, Tuman BA, et al. Type D personality, anxiety sensitivity, social anxiety, and disability in patients with acne: a cross-sectional controlled study. Postepy Dermatol Alergol. 2019 Feb;36(1):51-7.
- Singam V, Rastogi S, Patel KR, et al. The mental health burden in acne vulgaris and rosacea: an analysis of the US National Inpatient Sample. Clin Exp Dermatol. 2019 Oct;44(7):766-72.
- Tan J, Kang S, Leyden J. Prevalence and risk factors of acne scarring among patients consulting dermatologists in the USA. J Drugs Dermatol. 2017 Feb 1;16(2):97-102.
- Levy LL, Zeichner JA. Management of acne scarring, part II: a comparative review of non-laser-based, minimally invasive approaches. Am J Clin Dermatol. 2012 Oct 1;13(5):331-40.
- Grevelink JM, White VR. Concurrent use of laser skin resurfacing and punch excision in the treatment of facial acne scarring. Dermatol Surg. 1998 May;24(5):527-30.
- Boen M, Jacob C. A review and update of treatment options using the acne scar classification system. Dermatol Surg. 2019 Mar;45(3):411-22.
- Khunger N, Bhardwaj D, Khunger M. Evaluation of CROSS technique with 100% TCA in the management of ice pick acne scars in darker skin types. J Cosmet Dermatol. 2011 Mar;10(1):51-7.
- el-Domyati M, el-Ammawi TS, Medhat W, et al. Radiofrequency facial rejuvenation: evidence-based effect. J Am Acad Dermatol. 2011 Mar;64(3): 524-35.
- Ramesh M, Gopal M, Kumar S, et al. Novel technology in the treatment of acne scars: the matrix-tunable radiofrequency technology. J Cutan Aesthet Surg. 2010 May;3(2):97-101.
- Peterson JD, Palm MD, Kiripolsky MG, et al. Evaluation of the effect of fractional laser with radiofrequency and fractionated radiofrequency on the improvement of acne scars. Dermatol Surg. 2011 Sep;37(9):1260-7.
- Sardana K, Manjhi M, Garg VK, et al. Which type of atrophic acne scar (ice-pick, boxcar, or rolling) responds to nonablative fractional laser therapy? Dermatol Surg. 2014 Mar;40(3):288-300.
- Wu N, Sun H, Sun Q, et al. A meta-analysis of fractional CO2 laser combined with PRP in the treatment of acne scar. Lasers Med Sci. 2021 Feb;36(1):1-12.
- Al-Dhalimi MA, Arnoos AA. Subcision for treatment of rolling acne scars in Iraqi patients: a clinical study. J Cosmet Dermatol. 2012 Jun;11(2):144-50.
- Sapra S, Stewart JA, Mraud K, et al. A Canadian study of the use of poly-Llactic acid dermal implant for the treatment of hill and valley acne scarring. Dermatol Surg. 2015 May;41(5):587-94.
- Karnik J, Baumann L, Bruce S, et al. A double-blind, randomized, multicenter, controlled trial of suspended polymethylmethacrylate microspheres for the correction of atrophic facial acne scars. J Am Acad Dermatol. 2014 Jul; 71(1):77-83.
- Goodman GJ. Postacne scarring: a review of its pathophysiology and treatment. Dermatol Surg. 2000 Sep;26(9):857-71.
- El-Domyati M, Hosam W, Abdel-Azim E, et al. Microdermabrasion: a clinical, histometric, and histopathologic study. J Cosmet Dermatol. 2016 Dec; 15(4):503-13.
- Fabbrocini G, Annunziata MC, D’Arco V, et al. Acne scars: pathogenesis, classification and treatment. Dermatol Res Pract. 2010 2010:893080.
- Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science. 1983 Apr 29;220(4596):524-7.
- Hession MT, Graber EM. Atrophic acne scarring: a review of treatment options. J Clin Aesthet Dermatol. 2015 Jan;8(1):50-8.
- Agarwal N, Gupta LK, Khare AK, et al. Therapeutic response of 70% trichloroacetic acid CROSS in atrophic acne scars. Dermatol Surg. 2015 May;41(5):597-604.
- Walia S, Alster TS. Prolonged clinical and histologic effects from CO2 laser resurfacing of atrophic acne scars. Dermatol Surg. 1999 Dec;25(12):926-30.
- Majid I, Imran S. Fractional CO2 laser resurfacing as monotherapy in the treatment of atrophic facial acne scars. J Cutan Aesthet Surg. 2014 Apr;7(2): 87-92.
- You HJ, Kim DW, Yoon ES, et al. Comparison of four different lasers for acne scars: resurfacing and fractional lasers. J Plast Reconstr Aesthet Surg. 2016 Apr;69(4):e87-95.
- Brown JJ, Bayat A. Genetic susceptibility to raised dermal scarring. Br J Dermatol. 2009 Jul;161(1):8-18.
- Gauglitz GG, Korting HC, Pavicic T, et al. Hypertrophic scarring and keloids: pathomechanisms and current and emerging treatment strategies. Mol Med. 2011 Jan-Feb;17(1-2):113-25.
- Alster TS, Tanzi EL. Hypertrophic scars and keloids: etiology and management. Am J Clin Dermatol. 2003;4(4):235-43.
- Mutalik S. Treatment of keloids and hypertrophic scars. Indian J Dermatol Venereol Leprol. 2005 Jan-Feb;71(1):3-8.
- Alster TS. Laser treatment of hypertrophic scars, keloids, and striae. Dermatol Clin. 1997 Jul;15(3):419-29.
- Parrett BM, Donelan MB. Pulsed dye laser in burn scars: current concepts and future directions. Burns. 2010 Jun;36(4):443-9.
- Asilian A, Darougheh A, Shariati F. New combination of triamcinolone, 5-fluorouracil, and pulsed-dye laser for treatment of keloid and hypertrophic scars. Dermatol Surg. 2006 Jul;32(7):907-15.
- Atiyeh BS. Nonsurgical management of hypertrophic scars: evidence-based therapies, standard practices, and emerging methods. Aesthetic Plast Surg. 2020 Aug;44(4):1320-44.
- Mustoe TA, Cooter RD, Gold MH, et al; International Advisory Panel on Scar Management. International clinical recommendations on scar management. Plast Reconstr Surg. 2002 Aug;110(2):560-71.
- Hultman CS, Edkins RE, Wu C, et al. Prospective, before-after cohort study to assess the efficacy of laser therapy on hypertrophic burn scars. Ann Plast Surg. 2013 May;70(5):521-6.
- Guix B, Henríquez I, Andrés A, et al. Treatment of keloids by high-dose-rate brachytherapy: a seven-year study. Int J Radiat Oncol Biol Phys. 2001 May 1; 50(1):167-72.
- Tredget EE, Shankowsky HA, Pannu R, et al. Transforming growth factor-beta in thermally injured patients with hypertrophic scars: effects of interferon alpha-2b. Plast Reconstr Surg. 1998 Oct;102(5):1317-28; discussion 1329-30.
- Saray Y, Güleç AT. Treatment of keloids and hypertrophic scars with dermojet injections of bleomycin: a preliminary study. Int J Dermatol. 2005 Sep;44(9):777-84.
- Mrowietz U, Seifert O. Keloid scarring: new treatments ahead. Actas Dermosifiliogr. 2009 Dec;100 Suppl 2:75-83.
- Occleston NL, O’Kane S, Goldspink N, et al. New therapeutics for the prevention and reduction of scarring. Drug Discov Today. 2008 Nov;13(21-22):973-81.