Severe Retinal Damage and Choroidal Neovascularization Following Accidental Laser Exposure During Hair Removal: A Case Report.

Ocular injuries from cosmetic laser procedures are perhaps more problematic with regard to laser hair removal, given that some of the losses in vision may be significant and even permanent. Protective eyewear, for example, plays a very critical role in preventing such injuries. The following is a case report of a 24-year-old female technician who suffered serious retinal damage and consequent choroidal neovascularization (CNV) following accidental exposure to a laser hair removal device without wearing protective eyewear. She had first presented with a best-corrected visual acuity (BCVA) of 6/6 in the right eye and 6/60 in the left. An initial optical coherence tomography (OCT) had shown outer retinal damage. Within two weeks, she had a decrease of vision to counting fingers at three meters in the left eye, and it was diagnosed as CNV. Anti-vascular endothelial growth factor (VEGF) intravitreal therapy was promptly initiated. This case underlines the vital importance of very strict safety measures and timely intervention to manage laser-induced ocular injury effectively.

Insights From the Supreme Court Decisions: Undesirable Consequences After Minimally Invasive Cosmetic Interventions in Türkiye.

BACKGROUND: With the increasing demand for cosmetic procedures in recent years, the implementation of some of these procedures by unauthorized persons has led to undesirable results and subsequently to the creation of a large number of case files. AIMS: In this study, it is aimed to retrospectively evaluate the decision texts of the Turkish Supreme Court regarding minimally invasive cosmetic dermatology procedures and to evaluate the reasons and results of the applications reaching the high court in these procedures. METHODS: The Supreme Court's decisions in cases filed due to undesirable consequences caused by minimally invasive cosmetic interventions were scanned using the Supreme Court of Appeals' online database from 2013 to 2023. RESULTS: The majority of the procedures addressed by the lawsuits are carried out in beauty salons; laser epilation is the procedure that is conducted most frequently, and burns are the most prevalent complication (87.8%, 85.7%, and 77.6%, respectively). As an adverse event, 94.7% (n = 36) of burns occurred in beauty centers. Thirteen (26.5%) of the cases in our analysis were carried out by an unauthorized person. When laser epilation and other procedures are considered as two separate categories, in applications due to adverse events of laser epilation, 28 (66.7%) cases were concluded in favor of the defendant. CONCLUSIONS: Complications, especially burns, that occur after laser epilation performed by unauthorized persons in beauty salons constitute a serious caseload, and there seems to be a need for better control mechanisms to reduce this burden.

Physician Level Assessment of Hirsute Women and of Their Eligibility for Laser Treatment With Deep Learning.

OBJECTIVES: Hirsutism is a widespread condition affecting 5%-15% of females. Laser treatment of hirsutism has the best long-term effect. Patients with nonpigmented or nonterminal hairs are not eligible for laser treatment, and the current patient journey needed to establish eligibility for laser hair removal is problematic in many health-care systems. METHODS: In this study, we compared the ability to assess eligibility for laser hair removal of health-care professionals and convolutional neural network (CNN)-based models. RESULTS: The CNN ensemble model, synthesized from the outputs of five individual CNN models, reached an eligibility assessment accuracy of 0.52 (95% CI: 0.42-0.60) and a κ of 0.20 (95% CI: 0.13-0.27), taking a consensus expert label as reference. For comparison, board-certified dermatologists achieved a mean accuracy of 0.48 (95% CI: 0.44-0.52) and a mean κ of 0.26 (95% CI: 0.22-0.31). Intra-rater analysis of board-certified dermatologists yielded κ in the 0.32 (95% CI: 0.24-0.40) and 0.65 (95% CI: 0.56-0.74) range. CONCLUSION: Current assessment of eligibility for laser hair removal is challenging. Developing a laser hair removal eligibility assessment tool based on deep learning that performs on a par with trained dermatologists is feasible. Such a model may potentially reduce workload, increase quality and effectiveness, and facilitate equal health-care access. However, to achieve true clinical generalizability, prospective randomized clinical intervention studies are needed.

Standard operating protocol for utilizing energy-based devices in aesthetic practice.

BACKGROUND: Lasers and other energy-based devices are increasingly becoming popular in aesthetic practice. Many centers employ doctors or technicians to perform these procedures where treating doctor and operating doctor may be different. Hence the need for standard operative protocols, to be followed while performing these procedures to avoid mistakes, complications and to get optimum results. In the current review article, group of doctors who have worked with these energy-based devices over many years worked together and suggested the protocols to be followed for the most commonly used energy-based procedures. AIM: To provide Standard operating protocols for the operator and staff to ensure, efficacy, safety, for the patient and for the devices. METHODS: The following protocols have been drafted based on the best practices followed by the authors in their clinics and reflect their consensus opinion. The objective is to provide operating protocols in a standard format, which can be of use by practicing dermatologists and their staff. The protocols include both general guidelines for the laser room and specific protocols for different machines. The draft follows the following schema: General instructions for all the energy-based devices. Specific protocols for different devices: Laser hair removal, fractional lasers, Q-switched lasers, fractional microneedling radiofrequency and cryolipolysis. CONCLUSIONS: The protocols proposed help to maintain the uniformity and avoid complications. However, these instructions are generalized and not machine or lesion specific. There may be variations in the protocols depending on the treatment lesion and treating doctor as well as machine.

Laser hair removal complications and the associated risk factors at a tertiary dermatology center: a case-control study.

Laser hair removal (LHR) has been established as a safe and efficient method for eliminating unwanted hair. This study aimed to investigate the frequency of LHR complications and assess the contributing factors. During one year, 16,900 patients undergoing LHR therapy were evaluated for complications. For each case, two external controls were selected (matched based on age, sex, Fitzpatrick skin type (FST) III-IV, and the treated anatomical region). To assess the impact of anatomical region on complication occurrence, each patient was used as their internal control if another area was treated during the same session. GEE analysis was used for statistical analysis.The incidence of LHR complications was calculated to be 0.69%. The most common complications were petechia, purpura, and ecchymosis (31.66%) followed by pigmentation changes (20.0%). LHR complications were most commonly observed in the lower limbs (32.0%), face and neck (23.3%), and genitalia and thighs (22.3%), respectively. Possible risk factors were younger age (OR = 0.74, P-value ≤ 0.001), operating LHR in the head and neck (OR = 5.8, P-value = 0.022), utilization of the alexandrite laser (OR = 2.32, P-value = 0.011), and fluence in the Alexandrite laser (OR = 3.47, P-value = 0.003).Overall, the results of this study indicate that LHR is generally a safe method for removing unwanted hair. However, factors such as younger age, treatment of the facial area, and use of the alexandrite laser especially with higher fluence levels in patients with FST III-IV were identified as potential risk factors.

Unrecognized Cause of Native Valve Infective Endocarditis Due to Staphylococcus aureus: Laser Hair Removal.

Laser hair removal for esthetic purposes has commonly been performed worldwide. This procedure is considered to be safe and effective, and severe complications such as systemic bacterial infections have seldom been reported. We present a case of native valve infective endocarditis (IE) potentially associated with laser hair removal. A 32-year-old female with a history of childhood atopic dermatitis presented with fever and arthralgia. She had been receiving monthly total body laser hair removal treatments for nine months. Physical examination revealed numerous painful purpuras on her fingers and soles. Laboratory examinations revealed a positive troponin level, and a 12-lead electrocardiogram revealed ST-segment elevation in inferolateral leads. Transthoracic echocardiography revealed mild wall motion abnormalities from the mid-posterior wall to the apex and thickening of the anterior mitral valve leaflet. Blood cultures grew methicillin-susceptible Staphylococcus aureus (MSSA). Based on these findings, we made a diagnosis of native valve Staphylococcal IE and acute myocardial infarction due to septic embolism. Due to the progression of mitral valve destruction, she underwent mitral valve replacement surgery and received an eight-week course of antibiotics, leading to a successful recovery. This case highlights a potential association between laser hair removal and Staphylococcal IE. Laser hair removal may compromise the skin barrier, potentially allowing the entry of bacteria such as S. aureus. Increased awareness of this potential complication is necessary, especially in populations at high risk for IE. Further research is needed to investigate the link between laser hair removal and bacteremia, particularly in high-risk populations, to guide prevention strategies.

Angiokeratoma of Fordyce-A rare complication of laser hair removal: A case report of two patients.

Key Clinical Message: This study highlights the first documented cases of angiokeratoma of Fordyce following laser hair removal (LHR) emphasizing the importance of patient selection and careful laser use. It underscores the importance of understanding LHR-associated risks, particularly for patients with darker skin. The efficacy of topical rapamycin as an alternative treatment for angiokeratomas is also discussed. Abstract: Laser hair removal (LHR) has emerged as a widely accepted method for achieving long-term hair reduction. While generally considered safe, it is important to study the possible adverse events to optimize patient care. Here, we present a unique case report of angiokeratoma of Fordyce, a rare vascular lesion, following LHR. Two patients experienced the development of these lesions subsequent to LHR treatment sessions, characterized by a severe burning sensation during the procedure. Interestingly, both individuals exhibited varicose veins on their legs, suggesting a potential risk factor for this complication. Our findings highlight the importance of understanding the mechanisms underlying LHR-induced adverse events and the need for further research to elucidate associated risk factors and management strategies. This case report serves to enhance awareness among clinicians and emphasizes the significance of patient counseling regarding the potential side effects of LHR.

Evaluation of hair transplantation for improving unnatural hairlines after laser hair removal: A multicenter retrospective study.

CONTEXT: Laser hair removal treatment for hairlines with an unsatisfactory appearance often leads to an unnatural appearance; however, few studies have reported treatment outcomes. OBJECTIVE: To explore the satisfaction rate of laser hair removal involving the hairline. DESIGN: Retrospective analysis. SETTING: Data from 5 clinical institutions. PATIENTS: Patients (915; 630 female and 285 male) who underwent laser hair removal. INTERVENTIONS: Issues associated with hair removal were classified, and their proportions were calculated. Hair transplantation was performed to improve the appearance of different hairline issues. MAIN OUTCOME MEASURES: Relevant indicators of hair transplantation and postoperative effects. RESULTS: Overall, 82 patients were unsatisfied with their hairline appearance; of these patients, 58 underwent hair transplantation to improve the hairline. Additionally, demographic statistics showed that 68% and 32% of patients were in the 20 to 30 and 30 to 40 years age groups, respectively; there were no patients in the 40 to 50 years age group. Among female patients who underwent hair transplantation, 25% had a poor hairline position, 64% had a stiff hairline appearance, and 11% experienced both issues. Among male patients, 50% had a stiff hairline appearance, 28% had temporal absence, and 22% experienced both issues. Surgical treatment included moving the hairline forward and rebuilding the frontal curves. All patients were satisfied with hair transplantation outcomes. CONCLUSIONS: Laser hair removal can result in diverse types of unnatural hairlines. Hair transplantation has been proven to effectively improve the aesthetic appearance of the hairline.

Efficacy of laser hair removal in hidradenitis suppurativa: A systematic review and meta-analysis.

OBJECTIVES: Hidradenitis suppurativa (HS) is a chronic inflammatory condition characterized by painful nodules, draining tunnels, and fibrotic scarring in intertriginous, hair-bearing areas. The pathogenesis involves follicular occlusion and subsequent rupture, leading to uncontrolled inflammation. Treatment options for HS are limited and lack universal effectiveness. Laser hair removal (LHR) has been explored as a potential treatment; however, the efficacy and appropriate laser modalities remain unclear. This systematic review examined the efficacy and adverse effects of LHR in HS. METHODS: A comprehensive literature search was conducted from inception to September 2023 in Ovid MEDLINE, Ovid Embase, and The Cochrane Library (Wiley) with predefined inclusion and exclusion criteria, and a meta-analysis was conducted. RESULTS: Ten studies were selected (n = 227 total patients) and included six randomized controlled trials, two nonrandomized experimental studies, and two case series. Various laser modalities, including long-pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) (n = 115), intense pulsed light (n = 18), Alexandrite (n = 54), intralesional 1064 nm diode (n = 20), and combined fractional CO2 and long-pulsed Nd:YAG laser (n = 20), consistently demonstrated significant improvement in HS disease severity, irrespective of the disease scoring method used. Minimal adverse effects (primarily mild pain and erythema) were reported. A meta-analysis of three studies utilizing long-pulsed Nd:YAG laser demonstrated a standardized mean difference in disease severity of -1.68 (95% confidence interval: -2.99; -0.37), favoring treatment with LHR for HS. CONCLUSIONS: Hair follicles are key in HS pathogenesis and all included studies showed a significant improvement in HS disease severity after LHR regardless of the laser device used, likely related to hair follicle unit destruction. HS is a complex and heterogenous condition, and multiple disease scoring methods complicate outcome comparisons across studies. However, LHR, utilizing various techniques, is an effective treatment option for HS with minimal adverse effects.

Intraoral laser hair removal: A scoping review.

PURPOSE: Intraoral hair growth is a debilitating side effect of flap or graft-based oropharyngeal reconstruction. There is no standardized treatment, but groups have successfully eradicated unwanted hair growth with intraoral laser hair removal. This scoping review assesses the utility of laser therapy in managing this condition. METHODS: This scoping review followed PRISMA-ScR guidelines. Ovid Medline, Embase (Ovid) and Scopus were queried using index terms and keywords. Resulting articles were reviewed for inclusion by two independent reviewers against inclusion criteria and relevant data were extracted. RESULTS: The literature search yielded 297 articles, 22 of which met inclusion criteria. In total, 77 patients were treated: 38 patients with an Alexandrite laser, 19 with an Nd:YAG laser, 18 with a diode laser, and two with a CO2 laser. Complete response defined as 80% or more reduction in hair count was achieved in 70 patients (90%) and six patients (8%) achieved a partial response (10%-79% reduction in hair count). One patient (1%) with gray hair saw less than a 10% reduction in hair count. On average, 3.84 treatment sessions were needed, spaced 5.4 weeks apart. Treatments were well tolerated without major side effects. CONCLUSIONS: This is the first scoping review assessing the utility of intraoral laser hair therapy and suggests it may be a safe and effective treatment. However, surgeons should advise preoperative hair removal when clinically feasible to mitigate this side effect as much as possible.

Barriers to Completing Preoperative Hair Removal for Penile Inversion Vaginoplasty.

Penile inversion vaginoplasty (PIV) is a gender-affirming surgical procedure where the skin of the penis and scrotum is reconstructed into the neovaginal lining. To prevent hair-bearing skin from becoming incorporated into the neovaginal canal, transgender patients are encouraged to undergo hair removal of their external genitalia. The goal of this preoperative hair removal is to minimize the risk of potential hair-related complications after vaginoplasty. To better support patients seeking preoperative hair removal and identify current treatment barriers, we surveyed patients about their progress and satisfaction with hair removal. A cross-sectional survey was constructed to assess patient experiences with hair removal in advance of PIV. Sixty-seven patients met the inclusion criteria, of which 46 participated (68.7%). Both laser hair removal (LHR) and electrolysis were used. Although all patients had completed some preoperative hair removal at the time of survey (average of 14 sessions), the cohort completed only two-thirds of their total expected hair clearance. Multiple peri-procedural pain management therapies were employed, but overall satisfaction with pain management was low (57.4 ± 5.0 out of 100). LHR was associated with significantly lower procedural pain compared to electrolysis (p < .001). The average global satisfaction with the hair removal process was 57.9 ± 5.7 and incidents of mistreatment were associated with a statistically significant reduction in overall satisfaction (p = .02). Most patients felt that hair removal was important prior to surgery. Overall, LHR and electrolysis were both utilized as effective preoperative hair removal modalities; however, LHR has better pain tolerability than electrolysis.

Study on the efficacy and safety of a high-power triple wavelength diode laser (810, 940, 1060 nm) for removing fine and less pigmented facial hair on Asian skin.

INTRODUCTION: Performing laser hair removal treatments on dark skin is limited by the quantity of melanin within the skin. To minimize side effects, lower values of fluence are selected when using standard 755 or 810 nm diode lasers. However, this approach may limit the effectiveness of the procedure, particularly when treating areas with thin and less pigmented hair, which is often the case in facial regions. To improve results, high-power triple wavelength diode lasers can be used. This study aims to assess the efficacy, safety, and comfort of treatments that remove facial hair with a high-power triple wavelength diode laser (810, 940, and 1060 nm) in static mode on Asian patients with thin and less pigmented hair. MATERIALS AND METHODS: A single-center retrospective cohort study was carried out using a high-power triple wavelength diode laser (810, 940, and 1060 nm), with a 2.7 cm2 spot size, on faces with thin and less pigmented hair. The study comprised 23 subjects with Fitzpatrick skin types IV and V. Effectiveness was measured by counting the hairs that appeared in high-resolution photos taken prior to and following the procedure, in addition to the Global Aesthetic Improvement Scale (GAIS). Furthermore, mathematical 3D simulations were created on the COMSOL Multiphysics® software to allow for comparisons to be made with regard to thermal damage sustained by the hair follicles and epidermal heating. Assessments were also made in relation to side effects. RESULTS: An average of 66% hair reduction was observed. Patient satisfaction was between 4 and 5 points on the GAIS scale, indicating that the treatment was very well received and tolerated. Adverse side effects were not observed. CONCLUSION: It can be concluded that the use of a high-power triple wavelength diode laser (810, 940, and 1060 nm) is safe and effective for the treatment of very fine and less pigmented facial hair on Asian skin. Furthermore, a triple wavelength (810, 940, and 1060 nm) laser is absorbed less by the melanin in the skin, enabling the use of higher fluences in stamping mode, with greater efficacy and safety for darker skin.

Severe Burns of the Genital Area After Laser Hair Removal: A Case Report.

Burn injuries are among the most commonly observed complications of laser hair removal. Here, we present a case, in which severe massive burns were caused in the genital and perineal areas during such a procedure. The consequent scar formation led not only to negative aesthetic effects but also affected the physical and psychological health of the patient.

Changes in melanocytic nevi treated with laser hair removal: A systematic review.

BACKGROUND: Incidental treatment of melanocytic nevi during laser hair removal (LHR) has been noted to cause clinical and dermoscopic changes that may appear similar to findings seen in atypical or neoplastic melanocytic lesions. The rate and characteristics of these changes has not been well-studied. OBJECTIVES: The objective of this review article is to assess the literature for reported changes in melanocytic nevi following LHR to guide clinical practice. METHODS: PubMed was searched December 5, 2022 for articles evaluating changes in melanocytic nevi after LHR treatment using the following search terms: "nevi laser hair removal," "nevi diode," "nevi long pulse alexandrite," "nevi long pulse neodymium doped yttrium aluminum garnet," and "melanoma laser hair removal." All English language patient-based reports discussing incidental treatment of melanocytic nevi while undergoing LHR with a laser were eligible for inclusion, while reports of changes following hair removal with non-laser devices such as intense pulsed light were excluded. Studies evaluating non-melanocytic nevi such as Becker's nevus or nevus of Ota were excluded as were those evaluating the intentional ablation or removal of melanocytic lesions. RESULTS: Ten relevant studies were included, consisting of seven case reports or series and three observational trials, two of which were prospective and one retrospective. Among the seven case reports or series there were a total of 11 patients, six of which had multiple affected nevi. Clinical and dermoscopic changes to nevi following LHR appear to be common in clinical practice, though not well studied. Clinical and dermoscopic changes have been noted to present as early as 15 days after treatment and persist to the maximum time of follow up at 3 years. Commonly reported changes include regression, decreased size, laser induced asymmetry, bleaching, darkening, and altered pattern on dermoscopy. Histologic changes include mild atypia, thermal damage, scar formation, and regression. Although some of the clinical and dermoscopic alterations may be concerning for malignancy, to our knowledge, there are no documented cases of malignant transformation of nevi following treatment with LHR. LIMITATIONS: This study is limited by the low number of relevant reports and their generally small sample size, many of which is limited to single cases. Additionally, comparison of available data was limited by variable reporting of treatment regimens and outcomes. CONCLUSIONS: Changes to nevi treated during LHR are not uncommon. Modifications to nevi may occur and look similar to changes seen in dysplastic or neoplastic melanocytic lesions. Notably, despite the widespread use of LHR since the first device was Food and Drug Administration approved in 1995, a time span of nearly three decades, there have been no reported cases of melanoma or severe dysplastic changes within treated nevi. However, dermatologists should be aware that morphologic and dermoscopic alterations can occur after LHR to prevent unnecessary surgical procedures. Although melanoma has not been reported to occur in nevi treated with LHR nor with any other laser exposures, further long-term data is needed to fully elucidate this concern. Optimally, nevi should be examined by a dermatologist before LHR to determine a baseline clinical and dermoscopic morphology. If there is concern for potential atypia, laser should be avoided over such nevi to avoid confusion at future follow up visits.

Handheld dermatoscope versus digital camera for hair counts in laser facial hair removal.

The lack of uniform and objective techniques to evaluate treatment efficacy in photo-epilation studies leads to contradictory results. Thus, there is an urgent need to explore commonly accepted assessment tools. One of the most common methods uses hair counts via digital photography. However, macrophotography may not be able to depict the vellus-like hair induced by photo-epilation. On the other hand, handheld dermatoscopy is practical, affordable and offers high-quality magnification. Hair counts from a handheld dermatoscope and a digital camera were compared in 73 women who underwent 6 sessions with the Alexandrite 755 nm laser. Significantly more hairs were counted using the dermatoscope than using the digital camera (76.9 ± 41.3 vs. 58.6 ± 31.4, p < .005), independently of hair thickness and hair density. The difference in hair counts between the two instruments was inversely related to hair thickness and directly related to hair density. The handheld dermatoscope may be a more effective tool than the widely used digital camera in evaluating the response to laser hair removal treatment.

Novel laser hair removal in all skin types.

BACKGROUND: Laser has been long accepted as a solution for excess or unwanted hair growth yet traditional lasers are not always ideal for safe and effective outcome for all skin types and hair characteristics. A diode laser module combining three wavelengths (755, 810, and 1064 nm) in a single pulse was developed to provide a fast and long-term solution for subjects with various profiles. AIMS: To evaluate the safety and efficacy of a Triple wavelength diode laser module for hair removal treatment in all skin types (Fitzpatrick I-VI). SUBJECTS AND METHODS: This was a prospective, dual centered, single-arm study. Subjects were treated with a novel diode laser module. Thirty-six subjects were enrolled, sixteen with Fitzpatrick skin types I-IV (46%) and twenty with Fitzpatrick skin types V-VI (54%). Treatment areas were axilla and bikini lines. Subjects underwent 4 treatment sessions at 6 weeks ± 5 days intervals and attended a follow-up visit 3 months after the last treatment session. 2D digital photographs were taken at baseline and at the follow-up visit, and a hair count was conducted by three blinded evaluators. RESULTS: A significant reduction in hair count between baseline and the 3-month follow-up visit was observed in both axilla and bikini lines for all skin types. The mean hair reduction was 41.5 ± 19.4% and 48.1 ± 20.9% in the axilla and bikini line, respectively. A significant hair reduction was also observed within skin type groups; mean hair reduction 45.5 ± 16.9% and 40.3 ± 17.2% in skin types I-IV and V-VI, respectively, indicating similar efficacy for both light and dark skin types. No serious adverse events were reported. CONCLUSIONS: This study demonstrates that the Soprano Titanium laser platform is safe and effective for hair removal treatment in all skin types.

Comparative effectiveness of ice packs versus topical lidocaine-prilocaine mixture for pain control in laser hair removal of the axilla: A rater-blinded randomized controlled trial.

BACKGROUND: Laser hair removal is associated with moderate acute pain. OBJECTIVE: To compare effectiveness of ice pack to topical lidocaine-prilocaine for pain reduction during axillary laser hair removal. METHODS: Participants were randomly assigned to receive topical anesthetic to one axilla and ice packs to the other before each of 3, monthly 810 nm diode laser sessions. The primary endpoint was participant-reported pain on the visual analog scale (VAS) immediately following and 5 minutes after laser session. Posttreatment erythema, overall edema, and perifollicular edema were assessed by 2 blinded photoraters. Skin temperatures, patient preferences, and adverse events were recorded. RESULTS: Eighty-eight of 90 (98%) planned laser treatments were delivered and randomized. Participants reported higher VAS scores immediately after laser treatment with lidocaine-prilocaine compared to ice (P = .03). Five minutes after, participants reported higher VAS scores with ice (P = .03). After 53 of the 88 treatments (60.2%), participants reported preferring ice (P = .055). No serious adverse events were reported. LIMITATIONS: All participants were Caucasian or Asian with Fitzpatrick skin type I to III and coarse dark axillary hair, which may limit generalizability. CONCLUSIONS: While pain control with ice and topical anesthesia is associated with time after treatment, the 2 modalities do not differ in terms of degree of pain reduction associated with axillary laser hair removal.

Mechanism of crescent-shaped and ring-shaped epidermal damage from laser hair removal with cryogen spray cooling.

The safety and efficacy of laser hair removal have been well established through many clinical studies and through clinical use over the past 25 years. A laser hair removal device that protects the epidermis by utilizing cryogen spray cooling (CSC) is widely used internationally. In darker skin types, post-inflammatory hyperpigmentation (PIH) can occur after laser hair removal. In particular, laser hair removal with CSC is known to cause crescent-shaped or ring-shaped PIH. In this experiment, we report a visualization of this PIH mechanism. The laser used in this experiment is a 755-nm-long-pulsed alexandrite laser. Graph paper was treated with this laser to assess for thermal damage. We investigated changes in thermal damage due to differences in laser spot size, fluence output, and laser beam angle in relation to the graph paper. When using a spot size of 18 mm, we observed that higher fluences caused crescent-shaped thermal damage on the margins of the treated graph paper. It was also confirmed that when the hand piece is not held perpendicular to the skin, the laser-treated area is expanded and the CSC range is narrowed. These factors caused the area of thermal damage to widen. This widening causes ring-shaped thermal injury, leading to PIH. We treated graph paper using a hair removal laser with CSC to investigate the mechanism of crescent or ring-shaped thermal damage. Laser treatment on graph paper is effective as a test for defects in the CSC device. Factors that cause inadequate cooling, which leads to PIH, are large spot size, high fluence, not holding the laser hand piece perpendicular to the skin, and malfunctioning of CSC device.