June marks the beginning of Acne Awareness Month 2023, during which dermatologic and aesthetic medicine organisations aim to reduce stigma, spread awareness and elucidate possible treatment options for this common skin condition. Acne vulgaris is a chronic skin condition that, depending on its course, is characterised by the occurrence of skin eruptions, such as open and closed comedones, pustules, papules, and cysts; it is also one of the most common skin conditions globally, affecting more than 80% of adolescents, 50–60% of women aged 20–25 years, and 12% of women over 25 years (Chilicka et al, 2022). Alongside acne itself, the scarring resulting from the condition, which ranges in severity, is also a frequent presentation at clinics, estimated to affect clinically 55% of patients with acne (Tan et al, 2021). Acne merits its own treatment and management strategy, especially as scarring is associated with impaired psychosocial functioning and quality of life. Some 25.7% of Tan et al's (2021) cross-sectional survey participants felt less attractive or were embarrassed or self-conscious because of their scars; furthermore, 8.3% reported being regularly verbally and/or physically abused because of their scars, and 43.2% felt that their scars had negatively impacted their relationships (Tan et al, 2021). Thus, when consulting with a patient, it is imperative to correctly identify the type of scarring and consider patient-related factors, to thereby select the appropriate treatment modality to achieve the best possible results and alleviate any potential psychological distress they may experience.
Incorrect production and degradation of collagen during the healing process can lead to the development of various types of scars, which can be classified according to the cause and time of their formation and appearance. Acne scars fall into three broad categories: atrophic, which are recessed and below the surface of the skin; hypertrophic, which are raised above the skin surface; and keloidal, which often present as firm, rubbery nodules that extend beyond the initial site of trauma (Chilicka et al, 2022; McGinty and Siddiqui, 2023). Atrophic scars can be further divided into the following types: icepick, boxcar and rolling. Icepick scars have sharp edges, a width of not more than 2 mm and a V-shaped cross-section, with a narrowing deep into the skin; boxcar scars are large, flat and are often U-shaped or square, with a demarcated edge; and rolling scars, which can reach a diameter of 5 mm, are the largest of all types and give the skin a rolling or undulating appearance (Chilicka et al, 2022; West, 2023). All three types of atrophic acne scars may be simultaneously present in the same patient (Gupta, 2020).
Given the variety in scar presentation and severity, and the constant appearance of new technologies and modalities, it is important to review the most prevalent and commonly available options to be able to address patients' concerns with optimal efficacy.
Laser resurfacing treatments
Laser treatment of acne scars can be divided into two main categories: ablative and non-ablative (Table 1). Thermal injury delivered by lasers leads to stimulation of dermal fibroblasts, which initiates new collagen and elastin production, resurfacing the skin (Gupta et al, 2020). In darker skin types, lower energy should be used to minimise post-inflammatory hyperpigmentation (PIH) (Gupta et al, 2020); however, if PIH does occur, it can be managed successfully with topical agents, such as azelaic acid and hydroquinone (Levy and Zeichner, 2012).
Table 1. Different types of lasers used in post-acne scarring
| Ablative non-fractional | Ablative fractional | Non-ablative non-fractional | Non-ablative fractional |
|---|---|---|---|
| 10 600 nm CO2 (pulsed) | 1550 nm erbium doped | 1320 nm Nd:YAG1064 nm Nd:YAG | 1550 nm erbium doped |
| 2 940 nm erbium:YAG (pulsed) | 1540 nm erbium:glass | 755 nm picosecond pulse1450 nm diode | 1540 nm erbium:glass |
| 2 790 erbium:YSGG | 1440 nm diode-based laser | 585 nm pulsed dye595 nm pulsed dye532 nm KTPIPL 515–1,200 nm | 1440 nm diode-based laser |
Note: NoteS: YAG = yttrium aluminium garnet; KTP = potassium titanyl phosphate; IPL = intense pulse light; YSSG = yttrium, scandium, gallium and garnet.
Adapted from Gupta et al (2020)
Ablative lasers
Several traditional ablative lasers are used to treat acne scars: 10,600 nm carbon dioxide (CO2) lasers and 2940 nm pulsederbium-doped yttrium aluminium garnet (Er:YAG) lasers. The CO2 laser, either fully ablative or fractional mode, is appropriate to treat various conditions, alone or combined with other devices. Galal et al (2019) conducted a split-face study on 30 patients using a fractional CO2 laser and a fractional CO2 laser followed by platelet-rich plasma intradermal injections. In both groups, the effects were satisfactory; however, the synergy of the treatments contributed to a better improvement in atrophic scars, which was shown 3 months after treatment completion using a skin analysis camera (Galal et al, 2019). As with many scarring treatment modalities, combination therapies are typically much more efficacious than standalone treatments.
The pulsed Er:YAG laser (2940 nm) was developed as a less aggressive alternative to the traditional CO2 laser, as the laser ensures that all energy is absorbed in the epidermis and superficial dermis and causes less damage to the skin (Chilicka et al, 2022). With a fractional 2940 nm Er:YAG, pain and PIH incidence are lessened in comparison to the fractional CO2 laser; in a group of Indian patients, more than 25% improvement was demonstrated, with PIH seen in only one patient (Gupta et al, 2020). Cenk et al (2020) investigated the effectiveness of a series of four multifractional Er:YAG laser treatments in women and men with acne scars. At the end of the fourth session, the improvement rate was 26–50% in 14 of 24 patients and 51–75% in 10 patients (Cenk et al, 2020).
Non-ablative lasers
This group of lasers includes a pulsed dye laser (PDL) with a wavelength of 585 to 600 nm; ND:YAG with a wavelength of 1320 nm; and a diode laser with a wavelength of 1450 nm (Chilicka et al, 2022). The overall efficacy of ablative fractional lasers appears to be higher than non-ablative fractional lasers, with recent studies have reported scar improvement ranging from 26–50% versus 26–83% in non-ablative versus ablative fractional lasers, respectively (Gupta et al, 2020). However, PDL lasers are helpful in reducing boxcar scars, with the simultaneous elimination of blood vessels (Chilicka et al, 2022). Tanzi and Alster (2006) compared the 1450-nm diode laser with the 1320-nm ND:YAG laser by conducting a split-face trial with 20 patients with mild-to-moderate atrophic facial acne scars, who randomly received three monthly treatments with these respective lasers; the 1450-nm diode laser was thereby demonstrated to have a better clinical scar response. In a case report of a 42-year-old man, after laser treatment with a new 675-nm laser device, skin biopsies showed the proliferation of new collagen fibres in the treated area (Cannarozzo et al, 2021).
Chemical peels
Chemical peels, depending on their strength, coagulate proteins and target the epidermis and the epidermal–dermal interface, causing partial or complete necrosis (O'Connor, 2018). Trichloroacetic acid (TCA) is the one of the most effective and strongest acids, with a power of 0.26 in comparison to glycolic acid, which is 3.83 (Chilicka et al, 2022). A study evaluating the application of 70% TCA every 2 weeks in 53 patients with atrophic scars using the chemical reconstruction of skin scars technique reported good or very good improvement in 66% of patients (Agarwal et al, 2015). A parallel group trial comparing glycolic acid peels with glycolic acid cream and with placebo cream concluded that glycolic acid peels were effective for the treatment of atrophic acne scars, but repetitive peels (at least six times) with 70% concentration are necessary to obtain evidence of improvement (National Guideline Alliance, 2021).
Dermal fillers
Dermal fillers may be considered for boxcar or rolling atrophic acne scars, with insufficient evidence to support their use for deeper icepick scars, and are injected by various techniques, such as linear threading, depot, fanning, layering and tower (Gupta et al, 2020). Both immediate flattening and short-term improvement were noted in a study involving 12 patients with moderate-to-severe acne scars, with up to 2 mL hyaluronic acid gel, a temporary filler, was injected over three sessions, four weeks apart (Dierickx et al, 2018). Various semi-permanent and permanent fillers, such as calcium hydroxylapatite and polymethyl methacrylate, have also been shown to be effective, with the former causing improvement in boxcar scars (but not in icepick scars) and the latter demonstrating 64% versus 33% improvement when compared to placebo, respectively (Gupta et al, 2020).
Conclusion
There are a plethora of other treatment modalities for acne scarring not discussed here (Table 2), but combining different treatments, either sequentially or in the same session, has been shown to produce better outcomes. The type of treatment should be carefully chosen based on patient factors and scar presentation, but it has been suggested that the best results in scar reduction are achieved with treatments using lasers, radiofrequency, microneedling and platelet-rich plasma intradermal injections (Chilicka et al, 2022). As the condition's psychosocial impact is significant, and complete resolution of the condition is rarely achieved, patient expectations should be managed before commencement of any treatment. However, affected individuals should be reassured existing treatment options can achieve significant results, and it is encouraging that new and experimental treatments are emerging, such as autologous non-cultured dermal cell suspension injections and Jet volumetric remodelling (Gupta et al, 2022), which may show promise in the future.
Table 2. Clinical presentation of, and treatment options for, acne scars
| Scar type | Presentation | Treatment options |
|---|---|---|
| Icepick | Narrow (<2 mm) at the surface and tapers as they extend to deep dermis into the deep dermis or subcutaneous tissue |
|
| Rolling | Dermal tethering of abnormal fibrous bands which produces a dell in the skin; scars are 4–5 mm wide, sloped and with shallow borders |
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| Boxcar | Broad, round-to-oval or rectangular depressions, usually box-like depressions with sharply defined edges |
|
| Hypertrophic | Pink raised lesions that persist within the borders of the original site of injury |
|
Key points
- Although cosmetic and dermatological in nature, scarring from acne vulgaris can have a huge psychosocial impact on patients and merits its own treatment and management strategy. Many affected individuals report impacted body image, damaged relationships and verbal and physical abuse, attributed to their scars
- There is a wide variety in scar presentation and severity and a consistent emergence of new treatment technologies and modalities; therefore, it is critical to have an overview of the available options, to enable appropriate and effective person-centred treatment
- Albative and non-ablative lasers, chemical peels and dermal fillers are well-supported by the literature and have been demonstrated to be effective in treatment of atrophic acne scars; however, combining different treatments, either sequentially or in the same session, has been shown to produce better outcomes