The role of oculoplastic surgeons in minimally invasive cosmetic injectables.

PURPOSE OF REVIEW: In recent years, the field of aesthetic medicine has witnessed a paradigm shift with an increasing demand for minimally invasive cosmetic procedures, including cosmetic injectables. This review aims to delineate the distinctive role played by oculoplastic surgeons in the administration of cosmetic injectables, comparing their expertise to that of nonphysician practitioners. RECENT FINDINGS: Complications arising from cosmetic injections are discussed, including skin discoloration, inflammation, necrosis, vision loss, retinal pathology, and central nervous system adverse effects. Injector expertise, patient factors, type of filler, location of injection, and management strategies are reviewed. Findings highlight diverse practitioner involvement, common adverse effects like skin necrosis and vision loss, with hyaluronic acid fillers being prominent. Areas at the highest risk for ocular complication include the glabella and nose with potential management involving dissolving fillers and reducing pressure. Emphasis is placed on expert injector selection and patient awareness. SUMMARY: The administration of cosmetic injectables requires a profound understanding of facial anatomy, vasculature, and potential complications. In contrast to nonphysician practitioners, oculoplastic and aesthetic surgeons bring a level of anatomical precision and clinical acumen that is essential for navigating the complexities of cosmetic injectables. Emphasis on training and collaboration among practitioners will be essential in advancing the field while prioritizing patient safety and satisfaction.

Consideration of the diameter of superficial temporal arteries related to filler injections in the temporal region.

BACKGROUND: The concavity of the temple due to adipose tissue atrophy from aging accentuates the zygomatic arch and lateral orbital rim, leading to an aged appearance. The use of hyaluronic acid filler in the temporal region has gained popularity due to its procedural simplicity and consistent outcomes. OBJECTIVE: To evaluate the safety of administering hyaluronic acid filler in the temporal region concerning the frontal branch of the superficial temporal artery, which is at risk of injury. METHODS: Empirical observations were conducted on the internal diameter of the frontal branch of the superficial temporal artery, a critical anatomical site for potential injury. RESULTS: A significant proportion of the artery segments exhibited an internal diameter below 1 mm. Given that the outer diameter of an 18-gauge cannula is 1.27 mm, this method can be considered a relatively secure approach for enhancing the temporal region. CONCLUSION: The use of an 18-gauge cannula for hyaluronic acid filler administration in the temporal region appears to be a safe and effective method, with the potential risk to the frontal branch of the superficial temporal artery being minimal.

Complications, Treatment, and Outcomes of Self-Injecting Substances Into the Face: A Systematic Review.

BACKGROUND: The increased demand for minimally invasive facial cosmetic procedures in tandem with the ease of acquiring injectable cosmetics through direct-to-consumer retailers has led to a rise in self-injecting cosmetics among untrained individuals. OBJECTIVE: To analyze complications, treatments, and outcomes associated with self-injecting fillers into the face. METHODS: A systematic review of the literature from PubMed and Embase databases was performed from inception to September 10, 2022, to identify studies pertaining to self-injection of facial fillers. RESULTS: A total of 15 articles describing 38 complications among 18 patients were included in the data collection. The most commonly injected substance was hyaluronic acid (76.4%). The lips were the most common site of injection (33%). The most reported complication was edema (61%). Severe complications included acute vascular compromise (11%) and acute hearing loss (5%). The most common intervention was use of hyaluronidase and/or antibiotics (87.5%). Patients generally healed after treatment although residual localized hyperpigmentation was noted among 11% of patients. CONCLUSION: Injecting commercially available substances into the face is associated with potentially irreversible aesthetic, infectious, and vascular complications, especially in the hands of untrained consumers. Patients and providers should be aware of this dangerous trend.

Home-Use Hyaluronic Acid Jet Injectors: Unreliable and Unsafe.

BACKGROUND: Needle-free hyaluronic acid (HA) jet injectors are gaining popularity for rejuvenation treatment. The devices are widely available online and are used for self-injection or in beauty salons by nonphysicians. However, little is known about their performance and safety. OBJECTIVE: To explore the injection efficiency and cutaneous biodistribution patterns administered with home-use compared with medical jet injectors and to assess safety aspects. MATERIALS AND METHODS: The authors injected HA into ex vivo human skin with 4 home-use and 2 medical injectors. The intracutaneous dose of HA was calculated, and the cutaneous biodistribution of HA was assessed using a 3-dimensional Fluorescent Imaging Cryomicrotome System (3D-FICS). Safety aspects were evaluated based on the presence of a manual, CE (conformité européenne) mark, and sterility. RESULTS: The intracutaneous dose delivered by the home-use injectors was markedly lower compared with the medical injectors. 3D imaging for home-use injectors showed superficial epidermal distribution with low distribution volumes. For medical injectors, volumes were substantially larger and mainly middermal. All evaluated safety aspects were lacking. CONCLUSION: Results of this study suggest that the specific combinations of home-use injectors and HA used in this study are unreliable and unsafe, which casts doubts on the performance of these treatments in general.

Efficacy of a New Hyaluronic Acid Dermal Filler on Nasolabial Folds Correction: A Prospective, Comparative, Double-Blinded Clinical Trial.

BACKGROUND: Hyaluronic acid-based dermal fillers are the cornerstones of wrinkle correction and facial contour redefinition. OBJECTIVE: To assess the efficacy and safety of EST LF compared with RES L for the treatment of nasolabial folds (NLFs). MATERIALS AND METHODS: In this prospective, split-face, randomized, investigator and subject-blinded trial, 45 subjects with moderate-to-severe symmetrical NLFs were randomized to EST LF on one side of the face and RES L on the other side and were followed up for 9 months. The primary end point was change in WSRS score from the baseline to Month 1 (M1). Secondary end points included changes in WSRS score at other time points, aesthetic improvement, wrinkle volume quantification, adverse events, and local tolerance. RESULTS: The efficacy difference between EST LF and RES L at M1 was in favor of EST LF (-0.16, CI, -0.28 to -0.03]), demonstrating its noninferiority. Considering other time points, significant differences were observed at 3 and 6 months for EST LF , assessed with WSRS, GAIS, or NLF volume quantification. Both treatments were well tolerated. CONCLUSION: EST LF is effective and well tolerated for the treatment of NLFs.

One-Year Safety Evaluation of New Hyaluronic Acid Fillers (YYS Series): A Prospective, Multicenter, Observational Study.

BACKGROUND: With the continuous increasing availability of new filler products, each hyaluronic acid filler brand has distinctive pharmacokinetics, which may be associated with different complications. Therefore, the long-term safety of new generations of fillers should be evaluated. OBJECTIVE: This prospective, multicenter, observational, postmarketing study ( ClinicalTrials.gov identifier: NCT04738019) aimed to investigate the incidence of delayed-onset nodules and adverse reactions after the injection of new hyaluronic acid fillers (YYS series) into the facial skin. METHODS: Subjects scheduled to receive an injection YYS series filler were followed up for 52 weeks. The authors aimed to determine the incidence of a self-reported delayed-onset nodule-a visible or palpable nodule or mass at the injection site that was detected beyond the 14th day following the injection-during the 1-year follow-up period. RESULTS: Among the 1,022 subjects who received an injection of the YYS series, the incidences of delayed-onset nodules were 0% for YYS 360, YYS 540, and YYS 720. A 0.21% incidence (1 delayed hypersensitivity reaction) of a delayed-onset adverse reaction was noted for YYS 720, although none were reported for YYS 360 and YYS 540. CONCLUSION: In this study, a notably low frequency of adverse reactions associated with the YYS series was observed.

A Natural Flat Volumized Lips Filler Technique: Retrospective Analysis of 920 Patients.

BACKGROUND: Traditionally, hyaluronidase (HYAL) is used after hyaluronic acid (HA) injection to dissolve the undesired migration of product. OBJECTIVE: To describe a novel lip augmentation technique that uses HA and HYAL simultaneously in patients who previously had HA migration. METHODS AND MATERIALS: Nine hundred twenty female patients were included. In the first group ( n = 793), HA injections were performed in subcutaneous plane of the lips. In the second group who had previous product migration ( n = 127), 7.5 units of HYAL is injected in 4 points in ergotrid area before proceeding with HA injection. RESULTS: The medicis lip fullness scale scores after 2 weeks improved in all patients, while 92% of patients perceived the results as "very much improved" with Global Aesthetic Improvement Scale ( p ˂ .001). There was no difference between 2 groups regarding the patient satisfaction rates ( p ˃.05), while filler migration was seen in 0.2% ( n : 15) of patients in the first group during the follow-up period. CONCLUSION: The new vertical injection approach provided an increased vertical height, optimal eversion, and an incisor display on the lips. The simultaneous use of HYAL before HA injection seems to be a safe and effective practice in 1-stage treatment of the previously injected lips with filler migration into ergotrid area.

Post-Hyaluronic Acid Filler Reaction Treated With Abrocitinib: A Case Report.

Post-hyaluronic acid filler nodules are uncommon, unpredictable complications that present a challenge to clinical therapy. We report a case of a female in her fifties who developed edema and nodules 6 weeks after hyaluronic acid (HA) filler injection. After minimal improvement with oral steroids and intralesional hyaluronidase, a trial of oral abrocitinib was initiated, which yielded significant clinical improvement. Thus, abrocitinib may be a novel therapeutic option for delayed-onset nodules following injection of hyaluronic acid. J Drugs Dermatol. 2024;23(1):1355-1356.   doi:10.36849/JDD.7271.

A Retrospective Analysis of Patient Satisfaction With a Graft-Based Non-Surgical Rhinoplasty Procedure Using a Modified Surgical Rhinoplasty Module.

Non-surgical rhinoplasty, also known as liquid or injection rhinoplasty, utilizes hyaluronic acid-based fillers to offer a minimally invasive alternative to surgical rhinoplasty. Patient goals for injection rhinoplasty include improving various aspects of their nose, including the bridge of the nose, tip of the nose, shape of the nose in profile, and how well the nose suits the face. The purpose of this study is to use a modified surgical rhinoplasty questionnaire to analyze patient satisfaction and adverse complication rates of the authors' non-surgical injection rhinoplasty technique using a hyaluronic acid-based filler. A retrospective data analysis of 56 patients who had received a graft-based non-surgical rhinoplasty procedure between January 2019 and December 2019 was conducted. All procedures were performed at a single center by the primary investigator. Participants completed a questionnaire to assess for preoperative and postoperative satisfaction with their nose using a visual analog scale and modified "FACE-Q" module. Two-tailed paired t-tests and confidence intervals were calculated using bootstrapping/resampling techniques. Visual analog scale results depict a paired median difference of 4, yielding a P-value of 0.00001. Results illustrate that using a graft-based non-surgical rhinoplasty technique presents a promising alternative to surgical rhinoplasty that significantly improves patient satisfaction with their nose while ensuring minimal complication rates. Over 98% of patients indicated feeling "somewhat" or "very likely" to repeat the procedure. J Drugs Dermatol. 2024;23(1):1292-1296.     doi:10.36849/JDD.7073.

Effectiveness and Safety of a New Hyaluronic Acid Injectable for Augmentation and Correction of Chin Retrusion.

BACKGROUND: A hyaluronic acid (HA) filler intended for non-surgical improvement of chin appearance should ideally be of high strength/firmness (high G') to allow for deep injections on the bone. HASHA (Restylane Shaype) is a new hyaluronic acid (HA) injectable with high G' and high HA concentration (25 mg/mL), engineered by the new NASHA-HD (High Definition) technology. HASHA is suitable to be placed periosteally, aiming to mimic the natural shape of the bony chin. This pivotal clinical investigation evaluated effectiveness and safety of HASHA for augmentation and correction of chin retrusion.  Methods: Subjects 18 years or older with mild or moderate chin retrusion by the Galderma Chin Retrusion Scale (GCRS), were randomized 3:1 to HASHA (n=103) or no treatment (n=37). Assessments included GCRS (blinded evaluator), aesthetic improvement (Global Aesthetic Improvement Scale [GAIS]), subject satisfaction, and safety.  Results: GCRS responder rate (1-grade or greater improvement from baseline) was significantly higher for HASHA (83.3%) versus controls (10.8%) at month 3 (P<0.001) and maintained through month 12 (P<0.001). Aesthetic improvement was high throughout the study in the HASHA group, according to investigators (97% or greater) and subjects (89% or greater). Overall, subject satisfaction was high at month 3 and maintained at month 12. Product- or injection-related adverse events were mostly mild or moderate and transient. No product- or injection-related serious adverse events were reported. CONCLUSIONS: HASHA, a new NASHA-HD injectable with extra strength/firmness, was safe and effective for chin augmentation and correction of chin retrusion, with high aesthetic improvement and subject satisfaction throughout 12 months. J Drugs Dermatol. 2024;23(4):255-261.     doi:10.36849/JDD.8145.

The Efficacy of Three Different Oral Hygiene Regimens in Preventing Chemotherapy-Induced Oral Mucositis in Pediatric Patients Receiving Hematopoietic Stem Cell Transplantation.

BACKGROUND: Oral mucositis is one of the side effects developed post-hematopoietic stem cell transplant. This retrospective study aimed to assess the efficacy of a mouthwash mixture (lidocaine, sodium alginate, sucralfate, pheniramine) versus hyaluronic acid and a solution of sodium bicarbonate in terms of healing time and weight gain in the treatment of oral mucositis in pediatric patients undergoing allogeneic hematopoietic stem cell transplantation with hemato-oncological malignancies. METHODS: A total of 171 patients that received chemotherapy for the hematopoietic stem cell transplant were divided into three groups; group 1, treated with a mixed mouthwash of lidocaine, sodium alginate, sucralfate, and pheniramine; group 2, treated with hyaluronic acid; and group 3, treated with an aqueous solution of 5% sodium bicarbonate. Weight and mucositis scale scores derived from medical records of patients. RESULTS: There was a statistically significant difference in the mucositis scale scores between the groups on the transplant day and days 5, 10, 15 and 20 after the transplantation. At these measurement points, Group 2 (receiving hyaluronic acid) had a lower score, and Group 3 (who received sodium bicarbonate) had a higher score, especially on days 5 and 10 after the transplantation. CONCLUSION: The results suggest that hyaluronic acid is a more effective treatment option than the other oral care solutions that are frequently used for prophylaxis and treatment of oral mucositis.

A Rare Complication of Temporomandibular Joint Viscosupplementation Associated With the Intra-Articular Agent: A Case Report.

Viscosupplementation, which has been referred to as intra-articular injections of hyaluronic acid, is preferable in the treatment of patients with degenerative disease of the temporomandibular joint who have not responded to conservative therapy. The complications of intra-articular injections are reported as pain, swelling, heat, rash, itching, bruising, or redness. This article describes a patient who underwent arthrocentesis followed by viscosupplementation and subsequently experienced pain and malocclusion related to the applied agent.

Association between intra-articular hyaluronic acid injections in delaying total knee arthroplasty and safety evaluation in primary knee osteoarthritis: analysis based on Health Insurance Review and Assessment Service (HIRA) claim database in Republic of Korea.

BACKGROUND: The prevalence of knee osteoarthritis (KOA), a progressive degenerative disease, is gradually increasing, and it is a progressive degenerative disease. In patients with mild-to-moderate KOA, intra-articular hyaluronic acid (IA-HA) has been shown to be an effective non-operative treatment option that can provide significant pain relief and symptom improvement by increasing intra-articular viscoelasticity. This study aimed to evaluate the efficacy of IA-HA injections in delaying total knee arthroplasty (TKA) and the safety of IA-HA according to IA-HA type and combination with intra-articular corticosteroid (IA-CS) using a large health insurance claim database. METHODS: For this retrospective cohort study, the study population included patients aged ≥ 50 years with a first diagnosis of KOA between 2009 and 2014, who underwent TKA by 2020, using the Health Insurance Review and Assessment Service claim database in Republic of Korea. IA-HA injections were categorized as single or multiple injection regimen agents. Cox proportional hazard models estimated hazard ratios (HR) for TKA risk, adjusted for covariates. Logistic regression assessed the occurrence of adverse events after IA-HA administration. RESULTS: In all, 36,983 patients were included. Patients who received IA-HA injections had a significantly longer time to TKA compared to those who did not (mean delay of approximately 1 year). The IA-HA group had a significantly lower risk of TKA (HR: 0.61, 95% CI: 0.60-0.62) than non-IA-HA group after adjusting for covariates, which included age, sex, medical history, number of hospital beds, and CS injection. Single injection IA-HA regimen agents showed the longest time to TKA and lowest risk (HR: 0.56, 95% CI: 0.53-0.59). TKA risk decreased with the number of IA-HA cycles. Adverse events occurred in 6.7% of IA-HA cases without CS, with very low incidence of infection. Multiple injection regimen agents (multiple injection regimen 7.0% vs. single injection regimen 3.6%) and concurrent IA-CS use (concurrent IA-CS use 13.9% vs. IA-HA only 6.7%) were associated with higher infection risk. CONCLUSION: IA-HA injections were associated with a significant delay in TKA among patients with KOA. Single-injection regimen agents had the lowest TKA risk. Infection risk increased with multiple injections and concurrent IA-CS use. These findings could suggest the use of IA-HA as an effective non-operative intervention option for managing KOA and delaying TKA. Careful selection of IA-HA type and consideration of concurrent IA-CS use could play a role in delaying the time to TKA and reducing complications.

Isolated Ophthalmoplegia After Periorbital Hyaluronic Acid Filler Injection.

Facial filler injections are the second most commonly performed in-office cosmetic procedure. Vision loss is the most feared complication of hyaluronic acid (HA) filler injection, but isolated ophthalmoplegia can also occur. We report the case of a 45-year-old woman who developed nausea and diplopia following HA filler injection to the bilateral periorbital region. She presented with a left hypertropia and left-sided motility deficit without vision involvement. MRI of the orbits demonstrated mild enhancement and enlargement of the left inferior rectus and inferior oblique muscles. Treatment consisted of hyaluronidase injection and oral steroids. HA filler can cause isolated ocular misalignment and diplopia without associated vision loss. Patients should be counseled on these risks before undergoing soft tissue augmentation of the face with HA filler.

Aesthetic Surgical Pathway in Permanent Facial Filler Removal.

Although permanent fillers have been introduced in order to get long-lasting results, many studies have shown numerous severe and disfiguring complications. Nonsurgical procedures may mitigate those adverse events but the only way to remove the filler previously injected is represented by surgical excision. We present a pathway of facial surgical accesses to be performed achieving two goals: permanent filler removal and restore facial aesthetic balance. The proposed surgical accesses are already standardized in aesthetic surgical practice in order to avoid direct excision and unpleasant facial scar. A total of 231 patients underwent surgery for permanent filler removal and aesthetic restoration of the involved facial area, represented by forehead, glabella, nose, cheeks, eyelids, chin, jawline, and lips. Magnetic resonance evaluation was performed with the exception of lip patients who were evaluated with ultrasound. Postoperative follow-up was 12 months to 6 years. Subjective and objective methods were used for outcome evaluation according to the FACE-Q questionnaire. Functional and aesthetic correction was scored using the patient-graded Global Aesthetic Improvement Scale (GAIS), overall patient satisfaction was assessed by a five-point scale questionnaire. Functional and aesthetic restoration was globally recognized as improved according to the GAIS. Patients reported high levels of satisfaction assessed by a five-point scale questionnaire. A very good satisfaction level was registered in both subjective and objective judgment scores. To the best of our knowledge, we present the largest case series regarding surgical removal of permanent facial fillers. A proper preoperative evaluation, filler removal followed by restorative facial aesthetic surgery technique is paramount to approach challenging cases.

Comparative In Vivo Study of Solid-Type Pure Hyaluronic Acid in Thread Form: Safety and Efficacy Compared to Hyaluronic Acid Filler and Polydioxanone Threads.

INTRODUCTION: Although various products are commonly used for skin rejuvenation, solid-type hyaluronic acid (HA) as an injectable form has not been researched or utilized. This study aimed to demonstrate the safety and efficacy of solid-type HA in thread form, which differs from the conventional gel-type HA commonly used. METHOD: Solid-type HA threads, conventional HA fillers, and polydioxanone (PDO) threads were inserted into the dorsal subcutaneous layer of mice. Photographs were taken on days 0, 1, 3, and 7, and on day 7, the samples were harvested for histological analysis. Inflammatory reactions and detection of collagen were confirmed through tissue staining, and real-time PCR was conducted to quantify collagen synthesis. RESULTS: In the histological analysis, the PDO threads exhibited a greater inflammatory response compared to the HA threads. Masson's trichrome staining revealed a higher degree of collagen synthesis in the HA thread group compared to the HA filler group. While collagen type 1 expression was significantly higher in the PDO thread group than in the HA thread group, the HA thread group showed higher expression levels of collagen type 3. Furthermore, the PDO thread group demonstrated a statistically significant increase in TGF-ß1 compared to the HA group. CONCLUSION: This in vivo study demonstrated the stable application of solid-type pure HA threads and their potential for inducing collagen production, while also yielding a low inflammatory response. The findings highlight the promising applications of solid-type HA in the field of cosmetic dermatology. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Adverse Events Associated with Hyaluronic Acid Filler Injection for Non-Surgical Facial Aesthetics: A Systematic Review of High Level of Evidence Studies.

The article titled "Adverse Events Associated with Hyaluronic Acid Filler Injection for Non-surgical Facial Aesthetics: A Systematic Review of High Level of Evidence Studies" by Kyriazidis et al.in Aesthetic Plastic Surgery presents a systematic review focused on categorizing complications linked to hyaluronic acid (HA) dermal fillers. However, concerns arise about the methodologies employed in the reviewed studies. Precise knowledge of the active substance's properties is vital for treatment standardization. Gaining a comprehensive understanding of the key characteristics of the employed HA is of paramount importance to ascertain whether an association exists between these properties and the risk of complications. Understanding the rheological properties of HA, including viscosity, elasticity, and cohesiveness, is crucial for optimal facial filler selection. Acknowledging the authors' contributions, further analysis should encompass these factors.Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Adverse Events Associated with Hyaluronic Acid Filler Injection for Non-surgical Facial Aesthetics: A Systematic Review of High Level of Evidence Studies.

In response to the letter from Drs. Mataro and La Padula addressing our systematic review entitled "Adverse Events Associated with Hyaluronic Acid Filler Injection for Non-surgical Facial Aesthetics: A Systematic Review of High Level of Evidence Studies", we emphasize the deliberate scope of our research. Our review, grounded in rigorous Cochrane standards, specifically aimed to elucidate the adverse events reported in high-quality randomized control studies. While we recognize the importance of understanding HA's rheological properties for non-surgical facial aesthetics, our primary focus was on clinical outcomes and adverse events. Concerns insinuated about our methodologies based on the exclusion of rheological parameters are addressed, clarifying that such a decision was a deliberate scope limitation and not an oversight. We reaffirm the significance of our review and its contribution to the facial aesthetics field, promoting well-informed clinical decisions. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Nonsurgical Chin Augmentation Using Hyaluronic Acid: A Systematic Review of Technique, Satisfaction, and Complications.

The article titled "Nonsurgical Chin Augmentation Using Hyaluronic Acid: A Systematic Review of Technique, Satisfaction, and Complications" by Ou et al. in Aesthetic Plastic Surgery presents a systematic review focused on categorizing complications associated with hyaluronic acid (HA) dermal fillers. However, concerns arise regarding the methodologies employed in the reviewed studies. It is essential to have precise knowledge of the properties of the active substance for treatment standardization. Gaining a comprehensive understanding of the key characteristics of the HA used is paramount to determine if there is an association between these properties and the risk of complications.Understanding HA's rheological properties, including viscosity, elasticity, and cohesiveness, is crucial for selecting the most suitable facial filler. While we acknowledge the authors' contributions, we strongly believe that further analysis should incorporate these factors.Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Allergic Complications of Hyaluronidase Injection: Risk Factors, Treatment Strategies, and Recommendations for Management.

BACKGROUND: Hyaluronidase is used as a reversal agent for hyaluronic acid fillers and to increase the diffusion of other medications after infiltration. Cases of hyaluronidase allergy have been described in the literature since 1984. However, it is still frequently misdiagnosed. This review aims to summarize the current literature to describe the clinical picture of hyaluronidase allergy and identify any risk factors associated with its development, as well as provide recommendations for management in plastic surgery. METHODS: A digital search of PubMed, Scopus, and Embase databases was performed by two reviewers following the PRISMA guidelines. This search identified 247 articles. RESULTS: Two hundred forty-seven articles were identified, and 37 of them met the eligibility criteria. One hundred six patients with a mean age of 54.2 years were included in these studies. History of allergy to other substances (timothy grass, egg white, horse serum, penicillin, insect bites, wasp venom, thimerosal, potassium, histamine, phenylmercuric acetate, and nickel) and allergic diseases (asthma, dermatitis, atopy, rhinitis) was reported. A large portion of the patients with a history of repeated exposure (2-4) experienced the symptoms with their second injection. Nonetheless, there was no significant association between time to allergy development and the number of exposures (P = 0.3). Treatment with steroids +/- antihistamines resulted in the rapid and predominantly complete reversal of the symptoms. CONCLUSIONS: Prior injections or sensitization by insect/wasp venom might be the primary factor associated with hyaluronidase allergy development. The time between the repeated injections is not a likely contributor to the presentation. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .